RADIO-TIMETRAVELLER

Loop Calculations, Part 2

2011-12-26T17:35:00.000-05:00

Continuing the Quest for an Accurate Coil Inductance
-and The Mysteries of Distributed Capacitance

In Part 1 of this series we began our search for an accurate inductance formula. Accuracy is imperative in order to correctly predict our passive loop's inductance value and thus its tuning range. Passive loops for mediumwave are a special breed of coil animal. They could be termed "very large, very short coils", and they don't fit the common formulas found for calculating coil inductance.

Coils can basically be divided into two groups, long and short. The dividing line seems to be that 0.5 ratio of length/diameter. By coil length we mean the length of the winding as opposed to the diameter of the winding. If a coil's length is greater than half its diameter, it can be considered a long coil. If its length is shorter than half its diameter, it can be considered a short coil. The long coil inductance formulas put forth in the 1920s really didn't work well for short coils, those having a length/diameter ratio less than about 0.4. And the short coil formulas of the day only worked down to a length/diameter ratio of about 0.2, greatly losing accuracy below this. Our passive loop lies well south of 0.2, usually in the range 0.05 to 0.1. And it is usually square - not to our advantage as we swim in a sea of mostly circular coil formulas.

Wheeler's and other long coil formulas of the late 1920s were simple and accurate within the range of coil geometries for which they were intended. Many inductance calculators you find on the web use these formulas, despite the fact that there are far more accurate formulas for short coils. The problem with these calculators is there is no indication of coil geometry limitation, leaving the uninitiated to believe the result as accurate. Even Wheeler's short coil formula of this era, thought to be accurate to within 2%, was in later years revised upwards nearly 10% for some coil geometries!

At 79 years old and fourteen years before his death at age 93, Wheeler published in 1982 his continuous inductance formula, a single encompassing formula which calculates the coil inductance of all cylindrical coils, long and short. Using Grover, Wheeler and others work, and refined by Rosa's corrections and unmentioned scientists Lundin, Nagaoka, Knight and more, we have an accurate formula for predicting the inductance of coils with length/diameter ratios approaching that of a passive loop.

One would think we were done now - simply figure the tuning range of the passive loop using the calculated inductance. We have one more complication, however, and that is the loop's unknown self-capacitance. It must be accounted for in the second formula which calculates the tuning range of the loop.

Now we open that can of worms, that of self-capacitance, or commonly but erroneously known as distributed capacitance. Every coil also has self-capacitance as well as inductance. Self-capacitance is the inherant internal capacitance of the wire-formed coil itself. This spurious capacitance adds extra capacitance to the tuned circuit, changing (in fact further lowering) the resonant frequency. Additionally, this self-capacitance reduces the overall tuning range of the coil because it alters the range of the tuning capacitor. For example, if our common 10-365pF tuning capacitor is used in parallel with a proper loop happening to have 30pF of self-capacitance, the capacitive tuning range in reality is 40-405pF. What may have been a perfect, calculated tuning range of 530-1700 KHz is now altered downward to 500-1450 KHz. So, it is advantageous to design a loop with as little self capacitance as possible, or at least account for it in our design.

As stated, few formulas are commonly found which accurately calculate the inductance of a very large, very short coil like our passive loop antenna, whether it be square or circular. Virtually none of these account for coil self-capacitance, which, as we have seen, greatly changes the tuned circuit's operating parameters. An accurate self-capacitance figure is necessary to predict an accurate tuning range for our loop. Now we must wrestle with attempting to calculate or measure the loop's self-capacitance, which conceivably may change our tuning range by perhaps an additional 5-10 percent.

Much fact and fiction has been written concerning the cause and calculation of self-capacitance of coils. Once again, a little history is in order. Bear with me as I think you will find it interesting, especially if you like a bit of intrigue.

Little work if any had been done in this area of radio science much before 1920 - that of predicting coil self-capacitance. In 1917, J. C. Hubbard publishes a little-known paper in Physical Review entitled, "On the Effect of Distributed Capacity in Single-layer Solenoids". He measures coils of varying geometry down to a 0.2 length/diameter ratio, some with as few as 35 turns. He ponders that, "There is no evidence that the variation of ratio of pitch to diameter of wire [turns spacing] has a measurable effect on the distributed capacity in the region studied, though some effect is to be expected for coils of a smaller number of turns than those studied here."

S. Butterworth, famous innovator and designer of frequency filtering circuitry, tackles the problem again from 1922 - 1926. He publishes self-capacitance formulas which purport to cover single layer solenoids wound with round wire, the stipulations being that the number of turns have to be large (our long coil again) and well spaced.

In 1934, engineer A. J. Palermo enters with his text, "Distributed Capacity of Single-layer Coils", published in the proceedings of the Institute of Radio Engineers. In that text he presents a formula for calculating the self-capacitance of coils, based on his theory of accumulated inner-winding capacitance of a coil's adjacent turns. The paper is widely accepted by the engineering community of the day in both the scientific and popular press. The premise derived from his theory is that spacing of coil turns plays a major part in self capacitance, in that wider turn spacing lowers self capacitance, and tighter turn spacing increases it. Palermo claims to have found the solution. Has he?

Experimentation in the field continues. General Electric engineer R. J. Medhurst suddenly springs onto the scene in 1947 with his two-part article, "H.F. Resistance and Self-Capacitance of Single-Layer Solenoids" in Wireless Engineer. After exhaustive testing of self-capacitance on some 40 coils, Medhurst summarizes:

"These measurements show a very considerable divergence from the formula of A. J. Palermo though they are in quite good agreement with other previous experimental work [inferring Butterworth]. Self-capacitance of coils of this type is shown to be substantially independent of the spacing of the turns. It is given by an expression of this form:

Cd(picofarads) = H * D

where D(cm) is the mean coil diameter and H depends on the length/diameter. A table of H is given, based on these measurements."

"....to better than 5%, the measured values [of self-capacitance] fit the expression:

Cd(picofarads) = 0.46 * D

"....being independent of the spacing ratio."

Medhurst presents a table of values for H, covering coil geometries down to 0.1 length/diameter ratio. Accuracy below about 0.2 is still in question. It also seems that the most efficient length/diameter ratio causing the lowest self-capacitance in a coil is near 1.0, that is, a coil having a length equal to its diameter.

Medhurst explains further:

"Measurements of self-capacitance of a wide range of single-layer coils were consequently carried out. The results failed to confirm Palermo's claim that the self-capacitance varies steeply with the spacing of turns. They are, instead, in quite good agreement with previous work which had shown the self-capacitance to be very nearly independent of d/s (spacing ratio of diameter/turns)."

"Thus, the capacitance between adjacent turns will be less than that predicted by Palermo. The fact that self-capacitance is substantially independent of spacing of turns suggests that the part of the self-capacitance considered by Palermo is actually negligible."

At this, J. C. Hubbard remarked, "....we apparently have two quite independent factors [determining the self-capacitance of coils], one predominating greatly in very short coils, the other, in very long coils."

Medhursts's findings are approximate of course, though a rudimentary start to the overall understanding of the self-capacitance of coils. Experimentation continues through the next decades, each overwhelmingly refuting Palermo's theory. However, the myth of accumulated inter-turn capacitance has been cast and continues through the years, propagated through popular writing and idle commentary.

On his exceptional web site Dr. David Knight (G3YNH) delves into great detail concerning loop inductance and self-capacitance, both explaining and expanding upon current knowledge in the field. His articles on the current state of inductance calculation and self-capacitance of coils are well worth the read if you have a mathematical curiosity about such things.

The general thinking in past years has pointed to transmission line theory as being the root driving mechanism of coil self-capacitance. So interesting I find the huge amount of evidence against Palermo's supposition of turns spacing driving coil self-capacitance, I'll reproduce some of David Knight's eloquent analysis here. It makes for very interesting reading.

From David Knight's article, "The Self-Resonance and Self-Capacitance of Solenoid Coils", Version 0.01 (provisional), 9th May 2010, and "From Transmitter to Antenna, Inductors and Transformers: Solenoids, Part 1":

"Attributing self-capacitance to the static turn-to-turn electric field is a fallacy akin to taking the coil apart and trying to find the capacitor....The solution, of course, lies in recognising that the coil is a transmission line; except that the line in question turns out to be a rather complicated one."

"Unfortunately, the electrical literature abounds with articles which claim that the self capacitance of a coil is due to the capacitance between adjacent turns. This hypothesis is easily refuted, because it makes the wholly incorrect prediction that coils which have closely-spaced turns will have much greater self-capacitance than those which do not. The static component of self capacitance is small in single-layer coils, because a wave travelling along the wire does so with its electric vector nearly perpendicular to the coil axis, i.e., the electric field component parallel to the axis is almost negligible in comparison to the radial component. Nevertheless, the static capacitance idea appears to be so intellectually compelling, that there are at least two examples, in the peer-reviewed literature, where researchers have been motivated to fabricate or selectively report experimental evidence in order to support it."

"There is even a school of thought which says that the self-capacitance is due to the capacitance between adjacent turns; and although this is partly true for multi-layer coils, the hypothesis turns out to be a hopeless predictor of the reactance of single-layer coils. Experimentally, it transpires that self-capacitance increases as the spacing between turns increases...."

"Palermo gives a formula based on the hypothesis that the self-capacitance can be deduced by considering the capacitance between adjacent turns. Medhurst, being a meticulous experimenter, soon ran into difficulties with that approach; and so was forced to 'find out whether Palermo's formula did in fact agree with experiment'". He concluded that the data supporting Palermo's theory were suspect; and fell only a little short of accusing Palermo of scientific fraud.....Medhurst was aware that self-capacitance is substantially independent of turn-spacing provided that the coil has plenty of turns. He therefore chose to keep the number of turns per unit length high to eliminate pitch effects."

"A trivial investigation involving a Grid-Dip oscillator and a set of engineer's callipers will confirm that the various resonances exhibited by a disconnected coil are associated with the total conductor length. It is therefore extraordinary that the self-capacitance of single-layer coils is still routinely attributed to the static capacitance which is presumed exist between adjacent turns."

"Palermo reported a total of 19 self-capacitance measurements, 12 of which he carried out himself, and 7 of which were communicated to him by F W Grover of the National Bureau of Standards. It was in the group of measurements performed by Palermo himself that Medhurst found some of the numbers to be unreproducibly large....Medhurst was right to cry foul; but, in fact, the extent of the tampering was even greater than Medhurst had suspected."

"His [Palermo] formula often produces values which are much too large. In such cases, he appears to have adopted the habit of adjusting the calculated value downwards and the measured value upwards in order to obtain plausible agreement. Since he acknowledges the help of F W Grover however, he was evidently not in a position to tamper with the NBS data; and so in that case he confined himself to writing down false calculation results. In the worst instance, his formula gives 27pF, but he reports 12.9pF to confer with an NBS measurement of 12.8pF. There are other sleights of hand for those who wish to pursue the issue, but overall the paper is a travesty."

"That then is the insalubrious basis on which the inter-turn capacitance hypothesis became part of electromagnetic folklore. What Palermo hoped to gain by promoting his defective theory is difficult to guess; but he may have been motivated by inability to accept failure after an early success. His formula was subsequently turned into tables and abacs to 'assist' the radio engineer; and his dogma diffused naturally into the textbooks to lie in wait for the unwary. The 'capacitance between adjacent turns' hypothesis re-emerged in a new guise in 1999, in a paper by Grandi, Kazimierczuk, Massarini and Reggiani. These authors cite Medhurst, only to dismiss his work for being empirical; and make no mention of Palermo despite the strong parallel and Medhurst's barbed discussion."

"In summary, it is fair to say that theories which attempt to attribute the self-capacitance of single-layer solenoids to the inter-turn capacitance are wrong. In Palermo's case, the problem lies firstly in the assumption that a single wire can behave like two wires lying parallel, and secondly that the resulting capacitance should be divided by N [number of coil turns]. Logically, his theory is no better than a guess; which happens to work roughly for some coils, but has no actual predictive power."

How interesting and so anti the commonplace conception we have about self-capacitance so often found in the idle writing of today! We see that number of coil turns and spacing of coil turns matters very little in single-layer solenoid coils of many turns, so-called long coils. It is only when we get to the very short coil that matters begin to get sticky. Passive loop territory, again.

So where does this leave us? Even today, commonly-found formula predictors of self-capacitance still fall short of the mark of accuracy when dealing with in very short coils, coils having less than about 0.2 length/diameter ratio. Their result is often high by a factor of two and sometimes more. Over the years, Medhurst produced not one but several formulas for calculating self-capacitance for different coil geometries. Medhurst's original simple formula of Cd(picofarads) = 0.46 * D seems to give a nearly workable result in the region for very short coils. Two other Medhurst formulas purportedly come even closer in accuracy.

We have one additional way to predict, actually calculate, the self-capacitance of a coil. It is fail-safe in its accuracy. We first wind a test loop, then wire a tuning capacitor with known range to the loop. Using a receiver, we record the lower and upper frequency of the capacitor's tuning range by listening for signal or background noise peak at either extent of its range. Plugging the capacitor's known low and high values and the low and high tuned frequency extent into a simple (okay, maybe not so simple) formula, we can directly calculate the coil's exact inductance and self-capacitance. We then have a basis upon which to refine our calculation and thus the number of loop turns to satisfy our goal of tuning the mediumwave band completely.

Our last problem now is predicting the inductance of a very short, very large diameter square coil to a high degree of accuracy. We will take our best shot with Wheeler's Continuous inductance formula and Nagaoka's formula for circular coils, using Rosa's corrections for both, and then interpolate for a square loop. This, because we know that inductance varies very nearly proportionally with the area of the loop. A third formula we will use for comparison is a derivation of one of Grover's old formulas for polygonal square loops.

Next up in Part 3: The Inductance Calculator Program - Loop Calculator 1.0

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Bibliography:

Frederick W. Grover "Additions to Inductance Formulas", Scientific Paper #320, Bulletin of the Bureau of Standards 14, pp. 555-570 (1918).

Frederick W. Grover "Tables for the Calculation of the Inductance of Circular Coils of Rectangular Cross Section", Scientific Paper #455, Scientific Papers of the Bureau of Standards 18, pp. 451-487 (1922).

Frederick W. Grover "Formulas and Tables for the Calculation of the Inductance of Coils of Polygonal Form", Scientific Paper #468, Scientific Papers of the Bureau of Standards 18, pp. 737-762 (1922).

Frederick W. Grover "The Calculation of the Inductance of Single-Layer Coils and Spirals Wound with Wire of Large Cross Section", Proceedings of the Institute of Radio Engineers (1929).

Frederick W. Grover "Inductance Calculations: Working Formulas and Tables", (Van Nostrand, 1946 and Dover, 1962 and 2004).

Harold A. Wheeler "Simple Inductance Formulas for Radio Coils", Proceedings of the Institute of Radio Engineers, Vol. 16, No. 10, October 1928.

A. J. Palermo. "Distributed Capacity of Single-layer Coils", Proceedings of the Institute of Radio Engineers, Vol. 22, pp. 897 (1934).

H. Nagaoka, "The Inductance Coefficients of Solenoids", Tokyo, Vol. 27, No. 6, (1909).

E. B. Rosa, "The Self and Mutual Inductances of Linear Conductors", BBS Vol. 4, No. 2, (1908).

E. B. Rosa, Bulletin of the Bureau of Standards, Vol. 2, pp. 161-187 (1906).

E. B. Rosa and F. W. Grover, "Formulas and Tables for the Calculation of Mutual and Self Induction", [Revised], Bulletin of the Bureau of Standards, Vol. 8, No. 1, p. 122 (1911).

R. G. Medhurst, "H.F. Resistance and Self-Capacitance of Single-Layer Solenoids", Wireless Engineer, Feb. 1947, pp. 35-43 & Mar. 1947 pp. 80-92.

J. C. Hubbard, "On the Effect of Distributed Capacity in Single-layer Solenoids", Physical Review, 1917, Vol. 9, p. 529.

R. Lundin, "A Handbook Formula for the Inductance of a Single-Layer Circular Coil", Proceedings IEEE, Vol. 73, No. 9, pp. 1428-1429 (1985).

David W. Knight, G3YNH, "From Transmitter to Antenna, Inductors and Transformers: Solenoids, Part 1"

David W. Knight, G3YNH, "The Self-Resonance and Self-Capacitance of Solenoid Coils", Version 0.01 (provisional), 9th May 2010.

Loop Calculations, Part 1

2011-12-12T15:07:00.001-05:00

The Search for an Accurate Inductance Formula

Mediumwave DXers routinely use passive antenna devices to enhance signal pickup to a portable or handheld AM radio. Many of these are multi-turn loop antennas wound on a frame, usually square, some as small as 12 inches across. Tuned to resonance with a variable capacitor, the passive loop is placed in the near-field of the radio, coupling the enhanced signal to the radio's ferrite loopstick antenna.

The loop antenna is actually sensitive to the magnetic field and not the electric field of the transmitted signal. It outputs a voltage proportional to that field. Antenna performance is influenced by the number of turns and the area of the loop. For an air core loop, the bigger the loop, the bigger the signal voltage.

For the beginner or experimentalist wanting to construct a passive, air core loop, the question often arises: "How many turns of wire are required to tune the mediumwave broadcast band for a (_fill_in_the_blank_) sized frame?". Numerous formulas on numerous web sites can be found on the Internet. Some pages even include a Javascript or server-side calculator allowing different values to be plugged in and tried out. Results are generally close enough to get you in the ballpark, but can often be off as much as 20-30%. What gives?

How do these calculators work? Quite simply, they start by using one formula to calculate the inductance of the loop coil itself based on its side length (square coils), or diameter (circular coils), and number of turns. A second formula then takes this inductance value and the capacitance range of the tuning capacitor paired with the loop, then calculates the resonant frequency range (see The Simplified Frequency Formula) which the capacitor and loop combination will tune. Sounds simple, doesn't it. But there are complications. Oh, are there ever complications.

First we must calculate that crucial value of coil inductance. Accuracy is important if we are to have meaningful results. Over the last 180 years, a number of people have worked on the problem of inductance, and of finding an accurate inductance formula for coils, both small (in diameter) coils of various types, and the large air core coil - the passive loop which we mediumwave DXers use. It's been a long road. Here are the highlights:

In 1831, English chemist and physicist Michael Faraday, pictured at right, shows that changing currents in one circuit induce currents in a neighboring circuit, thus discovering induction. Over the next several years he performs hundreds of experiments and shows that they can all be explained by the idea of changing magnetic flux.

From 1856 through 1873, Scottish physicist and mathematician James Clerk Maxwell, pictured just below at left, develops the laws of electromagnetism, beginning with Michael Faraday's concept of a field of lines of force. Maxwell's calculations show that electromagnetic waves in a vacuum travel at the same speed as light; he correctly concludes that light is a form of electromagnetic wave, boldly predicting the rest of the electromagnetic spectrum. The time of America's Civil War, 1860-1865, is especially known for the advances Maxwell makes in the fields of electricity and magnetism.

He examines the nature of both electric and magnetic fields in his two-part paper on physical lines of force, published in 1861, in which he provides a conceptual model for electromagnetic induction, consisting of tiny spinning cells of magnetic flux. In 1873, he publishes his seminal work, Electricity and Magnetism.

Maxwell is considered by some to be the third greatest physicist of all time, behind only Isaac Newton and Albert Einstein. Great physicists are known for uniting theories into a single unified theory, and Maxwell did this with his formulation of classical electromagnetic theory. It leads to radio.

Finally, the twentieth century dawns and radio has been born. Engineers yearn for accurate formulas to calculate the inductance of coils. In the early part of the century, three names stand out prominently from the field of science as contributors to the art of inductance calculation.

Frederick W. Grover is perhaps the most prominent. Few photographs exist of this American physicist and electrical engineer. Grover worked as a physicist at the National Bureau of Standards starting in 1902, then side-tracked to study with Arnold Sommerfeld at the Ludwig Maximilians University of Munich in 1907. He was awarded his doctorate in 1908, and his thesis dealt with precision measurements and theory of eddy currents to determine a new method for finding the conductivity of metals. Upon receipt of his doctorate, he returned to the National Bureau of Standards. Grover's formulas, scientific papers and articles on induction form the basis of what we know today concerning the calculation of the inductance of a coil in its various forms. His book, Inductance Calculations (1946), is Grover's monograph for engineers and scientists engaged in the accurate calculation of self and mutual inductance. The book is based on the work carried out by Grover and E. B. Rosa during their distinguished careers at the National Bureau of Standards during the first half of the 20th Century.

Refining Grover's formulas was Edward Bennett Rosa, pictured at left. In 1901, Rosa was called to the newly-organized National Bureau of Standards, at Washington. There, as physicist, and later on, as chief physicist, he continued through the remainder of his life. When Dr. Rosa began his work in the Electrical Division of the National Bureau of Standards it was his ambition to determine a number of the fundamental electrical constants to a degree of accuracy far exceeding all previous determinations. One of these determinations was the ratio of the electromagnetic and the electrostatic units. This work was started early in 1907 and resulted in the most accurate determination yet made of this constant. Rosa, chief physicist, died suddenly while engaged in work in his office at the National Bureau of Standards on May 17, 1921.

Harold A. Wheeler also figures prominently, pictured with radios at right. During his university education in the early 1920s he worked part-time at the National Bureau of Standards Radio Laboratory. In 1924, Wheeler joined the Hazeltine Corporation, becoming head of its Bayside Laboratory by 1930. Under its auspices, he invented the automatic volume control for radio receivers, patented in 1932. Hazeltine spent the 1920s and 1930s working on various aspects of radio and TV technology. Wheeler enjoyed figuring out simple formulas for engineering questions: computing the inductance of a conductor, formulas for strip lines, transmission-line impedance curves. His formulas continue to be used today.

Most of the early inductance formulas developed were for small, round coils, that is, solenoid-wound, circular coils having a small diameter, with length that exceeds at least half the diameter (length/diameter ratio of 0.5 or more). These kinds of coils are more often found in radio circuitry. Our passive loop coil does not meet these specifications. It is usually larger by an order of magnitude or more, normally square or at least non-circular (polygonal in shape), and very short - with a length/diameter ratio approaching 0.1 or less.

Grover and others continued to work on the inductance riddle for years, eventually developing equations which approximately fit. I say "approximately" because as the length/diameter ratio approaches zero, the inductance curve becomes skewed and non-linear. A single equation would not fit the curve for all possibilities in this region of coil geometry where the length/diameter ratio edged below 0.5, the region of the "short coil".

Complications abound. Loop diameter, number of coil turns, wire spacing (also called pitch, or spacing between coil turns), and in some cases wire diameter all alter the final inductance of the coil, changing the resonant frequency range of the coil/tuning capacitor combination of our passive loop antenna.

Are we done? Hardly. A new complication arises. It is called self-capacitance, or distributed capacitance, which further changes the tuning parameters of our passive loop. It is an interesting and controversial subject, adding mystery to our loop calculation, as you will see.

Next up in Part 2: Continuing the Quest for an Accurate Coil Inductance

The Simplified Frequency Formula

2011-11-08T10:02:00.006-05:00

When I was a kid getting into radio and electronics, the only formula I knew to calculate the tuned frequency of an inductor and capacitor wired in combination was the tried and true formula dating back to the dawn of radio:

The result f is the frequency in Hertz of the tuned circuit (logically called cycles per second back in the day), L is the inductance in Henries, and C is the capacitance in Farads. Farads? Henries? Capacitors in the Farads range are huge, like railroad boxcars, they used to say. Coils in the Henries range are heavy (remember those 5U4GB tubed power supply filter chokes?). Conversely, inductance at mediumwave broadcast frequencies is measured in micro henries (millionths of a Henry, or µH) and capacitance is measured in pico farads (millionths of a millionth of a Farad, years ago noted as µµF). Wow, that's a mouthful.

Let's apply this old formula to a commonly-seen tuned circuit, a 240 µH inductor and a 365 pF capacitor wired in parallel. How confusing is this?

f = 1 / (2 * pi * Sqrt(.000240 * .000000000365)) [Sqrt = square root]

Now how many zeros am I supposed to add ahead of the 365 pF capacitor? The inductor?

I remember trying to work this formula before electronic calculators. Lots of zeros. Remember the time before electronic calculators? Okay, well, maybe you don't. Too many zeros to keep track of, in fact, too many zeros to keep track of even if working with a calculator. Oh, use scientific notation? Times ten to the minus what? Please show me (simply), at what frequency a 240 µH inductor and a 365 pf capacitor resonate?

Then one day, years later, I came upon the formula:

L * C * f * f = 25330

In the formula above, f is the frequency in megahertz, C the capacitance in pico farads, L the inductance in micro henries. 25330 will always be the same in every calculation. Inductance times capacitance times frequency times frequency will always equal 25330. Magic. Okay, now we're talking simplicity.

Using this formula, it's also very easy to change the operands around to calculate any one of the values, when the others are known.

Solving for Inductance (in µH):

       L = 25330 / (C * f * f)

Solving for Capacitance (in pF):

       C = 25330 / (L * f * f)

Solving for Frequency (in MHz):

       f = Sqrt(25330 / (L * C))

A few examples:

1. Find the resonant frequency of a 240 µH inductor and a 365 pF capacitor:

       .537 MHz = Sqrt(25330 / (240 * 365))

2. Find the inductance required to resonate at 530 KHz using a 365 pF capacitor:

       247.05 µH = 25330 / (365 * .53 * .53)

3. Find the capacitance required to resonate at 1700 KHz using a 247.05 µH inductor:

       35.47 pF = 25330 / (247.05 * 1.7 * 1.7)

Henry Thoreau said, "Simplify, simplify, simplify!". In this formula we have done that.

Can we make the original formula of old more workable to find frequency? Yes we can. Using our simple whole units of micro henries and pico farads, we use a multiplier at the end to get our result in KHz or MHz.

       f(MHz) = (1 / (2 * pi * Sqrt(240 * 365)) * 1000

       f(KHz) = (1 / (2 * pi * Sqrt(240 * 365)) * 1000000

That's a little easier to manage than the original without all the zeros. Should we rearrange the formula to calculate for inductance or capacitance? Well, we could. But why bother now that we have the simplified formula, L * C * f * f = 25330!

Now, why would we be wanting to calculate the resonant frequency of an inductor and capacitor? Let's say you plan to build a passive loop and want it to tune the mediumwave band. You've decided on a two foot square loop of 11 turns. Your loop calculator widget (or LCR inductance tester for those who can afford one) shows this loop to have a certain inductance. Pair that with your trusty old 365 pF broadcast tuning capacitor and using the frequency formula you can calculate the tuning range of the loop. Or roughly so.

We will have more on the topic of passive loop frequency calculations in a future article, including a custom loop calculator program. Stay tuned.

On the Road Again

2011-11-02T19:52:00.003-04:00

"On the road again...." Actually I have been "on the road again" since before I wrote last, and have completed the annual road trip west from New York to Arizona by way of Denver. The last of the Mediumwave Along the Erie Canal series was posted while enroute, from Fraser, Colorado on October 9th, while sitting in six inches of snow in the high Rockies.

Had a good trip. Saw some new mediumwave towers in Kansas and Colorado and photographed them. Am settled now in the southwestern desert an hour north of Old Mexico, just east of the Colorado River, and am back to contemplating our radio hobby and DXing again.

Check back soon for some new posts!

Mediumwave Along the Erie Canal, Part 3

2011-10-09T10:05:00.002-04:00

Continuing with our exploration of mediumwave station sites along the Erie Canal.

We are walking the Erie Canal path in the Rochester, New York area, headed west from Lock 33. Within a one mile stretch there are three mediumwave stations lining the canal. In the last part of this series we passed within sight of WHTK-1280.

Hiking along the canal past WHTK-1280 perhaps another half mile brings us to the Clinton Ave. overpass, situated just shy of the four-lane I-390 overpass. Poking above the trees to the north are the four equal height towers of WROC-950, and shown in the photo just below. Three are in direct alignment and the fourth sits off some distance broadside to the northeast. They are each .193 wavelength in height. Take the side path off the canal to the north about 50 yards and you have a good view of the tower site. WROC-950 is one of Rochester's oldest AM radio outlets. Both daytime and nighttime powers are set at 1KW.

The tower configuration at WROC is a bit curious. Three towers are used at night, those three in direct row alignment, broadcasting with a main lobe at 353 degrees, and a very minor lobe at 173 degrees. Gain in the favored direction, north towards the main population center, is 6.2dB.

Daytime coverage is bi-directional, using two towers, tower #3 from the aligned row and tower #4, the tower broadside to the northeast. The main lobes are at 343 degrees and 163 degrees, generating about 4.8 dB gain each.

WROC-AM's call sign is a reference to WROC-TV. While the stations are not and have never been co-owned, WROC-AM has an agreement with WROC-TV to provide local news coverage, and the borrowing of the WROC call signs from WROC-TV is included in this agreement. Coincidentally, the WROC-AM call sign was previously held at WHTK-1280 from 1961 into the 1970s, and was co-owned with WROC-TV while at that location.

WROC-950 began broadcasting in 1947 under the call sign WARC. It was an early affiliate of the ABC radio network, but later changed to a locally programmed, personality-driven popular music station. It was purchased by the B. Forman regional department store chain in 1953 and changed its call letters to WBBF, the last three letters of which stood for "Buy B. Forman". In 1966 it was sold to LIN Broadcasting for what was then a market record of over $2 million, but retained its popular music format and personality lineup until the early 1980s.

As WBBF, 950 AM was a popular Top 40 music station in Rochester, often leading the market in ratings surveys from the 1950s through the early 1970s, and ranking among the city's top stations through the late 1970s even after strong format competition arrived in 1972 from WAXC-1460 and later on the FM band from WPXY. Consistent success was achieved although as a relative latecomer to the AM band in the postwar era, WBBF's coverage area had to be restricted to the east and west to prevent interference with other stations on the same channel. In 1982, as hit music radio listeners were migrating to FM, the station evolved into a talk format. WBBF served a short stint as WEZO from 1998 to 2002, then adopting the WROC call sign. The WBBF calls are now in use in Buffalo, New York.

In September of 2004, WROC signed on with the liberal Air America network, having previously carried conservative talk. In September of 2008, WROC became an ESPN affiliate. The format is closely affiliated with Buffalo sister station WGR-550.

Shown below is WROC-950's nighttime pattern plot. On the plot are shown various co-channel stations around the region and where they fall into WROC's pattern.

This concludes this series. Hope you have enjoyed it.

Mediumwave Along the Erie Canal, Part 2

2011-10-01T19:13:00.002-04:00

Continuing with our exploration of mediumwave station sites along the Erie Canal.

We are walking the Erie Canal path in the Rochester, New York area, headed west from Lock 33. Within a one mile stretch there are three mediumwave stations lining the canal. In the last part of this series we passed within sight of WXXI-1370.

Walking just a little further along the canal path, coming into view is the four tower array of WHTK-1280 protruding above the Winton Rd. overpass, and shown in the photo just below. Its equal height .339 wavelength towers stand in a perfectly-aligned row at the northwest corner of Winton Rd. and Henrietta-Townline Rd. behind an industrial park, and just across the canal to the south. Passing under the overpass and walking about 100 yards further we get a great view of WHTK's towers.

WHTK-1280, also known as Sportsradio 1280, obviously airs a sports radio format. It is fully simulcast on WHTK-FM (107.3). WHTK is a Clear Channel Communications affiliate and is owned by Citicasters, Inc., featuring programing from Fox Sports Radio and Westwood One as well as New York Yankees, Rochester Americans and Rochester Red Wings games among other local and national sports. It transmits in AM-HD (IBOC). Both daytime and nighttime powers are set at 5KW.

Daytime coverage is omni-directional, using only one tower. The four tower array in use at night broadcasts with a main lobe at 346 degrees, and a minor lobe at 166 degrees. Gain in the favored direction, north again towards the main population center, is a respectable 7.5dB, pushing an effective 28.3KW towards Rochester.

The station was first known as WVET, signing on in 1947 under ownership of a group of returning World War II veterans calling themselves Veterans' Broadcasting Company. It operated successfully for many years with a personality full service adult popular music format. It changed callsign from WVET to WROC when Veterans bought WROC-TV from Transcontinent Television Corporation in 1961. Simultaneously an FM sister station, WROC-FM, signed on, first playing classical music and later automated jazz and pop standards. Veterans Broadcasting sold all the WROC stations in the mid-1970s. The AM station continued with its full service format until late in the 1970s, when it tried an all-news format first as WROC and then as WPXN (AM). It would later simulcast its FM sister station, by the early 1980s known as WPXY (FM) amd airing the personality contemporary hit music format which it still runs today. Late in the 80s, after changes in ownership, it would migrate to pop standards and then to mostly syndicated "hot talk", a lineup of talk and sports programming meant to appeal to young adult men. At that time it adopted the WHTK callsign (the "HTK" meant to stand for "hot talk") which it still uses today.

Shown below is WHTK-1280's nighttime pattern plot. On the plot are shown various co-channel stations around the region and where they fall into WHTK's pattern.

Stay tuned for Part 3 of this series.

Mediumwave Along the Erie Canal, Part 1

2011-09-21T07:41:00.007-04:00

Let's explore some mediumwave stations whose transmitter sites line the Erie Canal at Rochester, New York. Three sites are in such close proximity to the canal that their ground radials almost dangle in its waters.

The Erie Canal is a waterway that runs about 363 miles from Albany, New York, on the Hudson River to Buffalo, New York, at Lake Erie, completing a navigable water route from the Atlantic Ocean to the Great Lakes. The canal contains 36 locks with a total elevation differential of about 565 ft. It was first proposed in 1807, and remained under construction from 1817 to 1825.

The canal was the first transportation system between the eastern seaboard (New York City) and the western interior (Great Lakes) of the United States that did not require portage. It was much faster than carts pulled by draft animals, and cut transportation costs from $100 per ton to $10 per ton. The canal fostered a population surge in western New York state, opened regions farther west to settlement, and helped New York City become the chief U.S. port. It was enlarged between 1834 and 1862. In 1918, the enlarged canal was replaced by the larger New York State Barge Canal.

Canal boats were pulled by horses and mules along a towpath which ran alongside the canal. In modern days, the old towpath has been turned into a walkway for hiking and biking in many places. A one mile section along the Erie Canal through Rochester, New York plays host to no less than three mediumwave stations. Walking the canal, one passes within 500 yards of stations WXXI-1370 (5KW), WHTK-1280 (5KW), and WROC-950 (1KW).

Let's take a walk along the canal in this area and I'll describe what we see, radio-wise.

Pictured just below is the tower array of WXXI-1370. Starting at Lock 33 on Edgewood Ave. and proceeding west, after a few hundred yards we see WXXI-1370 off to the north about 500 yards and behind an apartment building just off of French Rd. WXXI's four towers stand in a rectangular trapezoidal-shaped array. Both daytime and nighttime powers are set at 5KW.

Daytime coverage is omni-directional, using only one tower. The four tower array in use at night broadcasts with a main lobe at 354 degrees, and a minor lobe at 157 degrees. Gain in the favored direction, north towards the main population center of Rochester, is just over 5dB. WXXI is one of those rare stations that reference all towers in their orientation, spacing, and phasing to a non-primary tower: Tower 2.

WXXI is Rochester's National Public Radio outlet on the AM band. It also broadcasts in HD on the FM band. WXXI dates its origins to July 2, 1984, when it signed on with a mix of NPR news programming, local news and talk, and public affairs programming geared to serve adult listeners in the six-county Rochester metropolitan area. The station is the successor to WSAY, a facility founded and built by the late Gordon P. Brown in 1936 as a small local area station with a 250 watt signal on 1210 kHz. It moved to 1240 kHz in 1941. In the pre-war era WSAY became best known as the home of local music programs at a time when its network-affiliated competitors were airing a mix of local news and sports with national drama, comedy and music/variety shows supplied by the NBC and CBS networks. WSAY also was the first station to hire an African-American announcer for a regular shift.

Following World War II WSAY received FCC permission to improve its signal by moving to the regional 1370 kHz frequency. It relocated its transmitter from a downtown Rochester building with rooftop antenna to a modern four-tower plant in suburban Brighton. It increased power first to 1000 watts and shortly afterward to 5000 watts full time. Over the next three decades WSAY operated under a number of formats, from pop standards to top 40 to progressive rock to country. Gordon Brown owned WSAY until his death in 1979, and his estate sold it to the Dickey family. The Dickeys operated it from 1980 to 1984, also under a variety of formats from personality adult contemporary to country to talk, eventually changing its callsign to WRTK. The license and facility was eventually sold to the WXXI Public Broadcasting Council, and briefly taken dark before its summer 1984 relaunch as WXXI-1370 with a round-the-clock non-commercial format of news, talk and public affairs. The WXXI news and public affairs department produces local newscasts seven days a week and local talk programming every weekday, along with NPR news programming and locally produced documentary and specialty offerings. It currently operates from modern digital studios in the downtown Public Broadcasting Center, and upgraded transmitting facilities at the Brighton location first brought on line by Gordon Brown in 1946.

Over the past 25 years WXXI-1370 has achieved success in attracting a sizable audience for its news and public affairs programming, consistently ranking second in audience size among the Rochester market's AM signals and second among stations on either AM or FM with spoken-word (news, talk, or sports) formats according to Arbitron quarterly audience measurements. It has also won numerous local, state and national awards for its program offerings.

Shown below is WXXI-1370's nighttime pattern plot. On the plot are shown various co-channel stations around the region and where they fall into WXXI's pattern.

Stay tuned for Part 2 of this series.

Mexican Governmental Mediumwave List Updated

2011-08-10T09:14:00.003-04:00

About a month ago, the Mexican government finally updated their official mediumwave station list, now dated June 30, 2011. Updates to this list do not come very often, perhaps every year or so. The previous list was dated December 31, 2009, 18 months ago. It's been a long time coming.

The list, in .PDF format, documents station location (city and state), owner, call sign, frequency, daytime and nighttime powers, and license expiration date or status. It is unfortunate that actual latitude and longitude coordinates of transmitter sites are not included. However, latitude and longitude can be extracted from the matching entry in the US FCC database if you look carefully and wade through the huge number of redundant and outdated Mexican records to find the right one. I am working on creating a combined list using my Radio Data MW program. That will allow the creation of a list in many forms, sorted at will by call sign, frequency, power, location, signal strength, etc.

To my knowledge, Mexico does not maintain an internet downloadable, official database in file form like the FCC or Industry Canada does. It would be nice if they did.

Mediumwave DX Meets the eReader

2011-08-09T19:10:00.004-04:00

We have seen how to create personalized station lists at no cost in the first installment of this series. We can even create a file system of antenna pattern plots. But, as stated, who wants to print all of this and haul it around, not to mention the expense of all the paper and ink?

A couple of ideas come to mind. Save the desired station lists and pattern plots to a flash drive, then take it and our laptop to the field where we will have access to the information. But even a laptop is cumbersome to haul around when you are already carrying radios, headphones, loop antennas, wire, etc. And a laptop generally only has a battery life of a couple of hours before it is dead.

A number of years ago I toyed with the idea of loading text files on a PDA (Personal Data Assistant) device, like a Palm Pilot. There were ways to do this at the time, and you had to be a bit of a geek to figure it out. My idea was to load station lists and other textual documents for reference in the field. But upon further examination, it seemed like reading text on such a tiny device with poor screen resolution was not the way to go. I resisted, waiting for technology to advance. It did.

The dedicated ereader device appeared. At first they were cumbersome to use, and extremely proprietary - having almost no support for anything but books. Finally a couple of years ago the market shifted directions. Manufacturers had at last gotten the word that the public wanted some versatility in their ereader. Text files and .PDF files became compatible and well-supported, along with a host of other common file types like HTML, images, and video.

And with that direction change came the Kindle 3 by Amazon and the Nook Color by Barnes and Noble. I bought a Nook Color. It cost $250. Natively, it will display text files and HTML files, as well as .JPEGs and other image formats. It has a marvelous .PDF viewer. Most of these modes have zoom capability, making viewing easier. Amazon's Kindle 3 ereader device has similar features, though getting .PDFs and text across to them is a little quirky. Tablet computers also abound today, like Apple's iPad2 and the Samsung Galaxy. Virtually all have the ability to handle these same file types.

So, we are set. What we will do is load our saved station reference files to our ereader device. The 7-inch Nook Color ereader is small, the size of a paperback book, and thin, hardly 1/2 inch thick. It is ultimately portable, and can be carried easily wherever we want to go.

The ereader with its 8 gigabyte memory can hold the entire US mediumwave station reference if we choose, and many times over. And that includes the antenna pattern plots if we elect to save them too. No paper, no ink. It can be carried anywhere. Its battery life can be 8 hours (Nook Color, LCD display) to almost a month with one hour per day of reading (Kindle 3 or Barnes and Noble Simple Touch, both e-ink displays). Files are usually searchable. This means that you can locate a frequency or station call sign or format or whatever you are searching for quickly. Not as easy with a 500+ page paper volume.

The only requirement is that we come up with some sort of way to arrange our mediumwave files in an organized fashion so we can have quick access to them. Easily done.

Some ideas on file arranging:

1. Create folders named by frequency or by frequency block (range) to hold station files.
2. Create folders by state name to hold station files from that state.
3. Create folders by city name to hold station files from that city area.
4. Name the files themselves to include call sign and frequency to aid in recognition.

Our master copy folder and file scheme can be created on the laptop and housed there for safe keeping. It will be a simple matter of transferring the master database over to the ereader by dragging and dropping files or folders from one unit to the other when the ereader is cabled to the laptop through the USB port.

For those that have tablet computing devices instead of dedicated ereaders, the procedure would be similar. I am convinced the ereader or tablet device is the way to go for taking mediumwave station lists to the field. Give it some thought.

Mediumwave Station Reference Lists

2011-07-30T05:38:00.010-04:00

I DX a lot outside, whether on the road in a vehicle or just to be outside and away from the extreme household noise that we find today. Whether you be a mediumwave DXer, shortwave DXer, or DXer of another kind, the problem in DXing away from home has always been the lack of ready DX reference materials nearby. You have to pack and carry all that stuff. And I like to travel light. My outdoor DXing is often casual and spur of the moment, with a ULR or portable. Who might that weak station be under KHOW-630? I need a station reference.

At minimum, a reference guide of stations helps you to know what to look for and what to expect, so it is important to have one close by. In recent years there were two common radio DXer guides in bound-book form, the World Radio TV Handbook (WRTH) and Passport to Worldband Radio. I used to buy them faithfully every year. Passport had a great radio review section, but its station reference only covered the shortwave bands. Passport also folded last year and ceased publication. It was a great shortwave guide.

WRTH covers longwave to 30 MHz and also FM and TV, listing nearly every broadcast radio and TV station a country has. Unfortunately, its US mediumwave coverage is not complete, in that it doesn't cover many lower powered and graveyard stations. The information is scant, basically only station addresses, power, and antenna type. The recent list price: $35.00 per issue, though it can be had at a discount later in the year. That's a lot of dollars for a little bit of usable information if you are just interested in mediumwave.

The National Radio Club publishes its AM Radio Log every year, and it's a winner. The current, 32nd edition of the log contains some 300 pages in 8.5 x 11 inch size, 3-hole punched, in U.S. loose leaf format. Current cost is $20 for members and $26 for non-members.

The NRC also publishes an Antenna Pattern Book, helpful in determining which direction stations are favoring in their broadcast pattern. The current, 6th edition (late 2005 data) is 238 pages containing both daytime and nightime patterns for stations in the US, Canada and parts of Mexico. It is in the same format as the AM Radio Log, and is designed to be used as a companion to it. The "book" fits in a 1 inch three ring binder. The current cost: $17 for members and $23 for non-members.

We are starting to accumulate a lot of paper (500+ pages so far). And the cost is going up. As you can see, reference guides can be expensive to buy. They also go out of date quickly. Thirdly, they can be heavy and take up a lot of space. We are back to the packing and carrying problem.

In the article, Radio Station Databases 101, we explored several countries' mediumwave databases which might help us in creating our own lists of mediumwave stations to aid us in our DX quests.

However, database information is not generally in a readable format. In most cases it is hundreds or thousands of lines of incomprehensible textual data. It is mainly useful to the software hobbyist who might want to write a database program or create an XCEL file to display station information in various sorted forms. This is obviously a highly technical and tedious endeavor which most people are not equipped or trained to do. My own project in this area is the Radio Data MW program. I will write more on this project at a later date.

Thankfully, a number of web sites exist which have done much of the work for us, tabulating this data and presenting it in one form or another which can be useful as a reference. These web pages, or in some cases, files, can simply be printed and placed into a binder of some sort, then used in your shack or carried to an outside DX location and used there. We have at least saved cost, though not paper.

Let's explore what's available for free on the web.

Pre-eminate in the field, the FCC maintains an AM Query web page that utilizes and searches its standard database for all US stations - AM, FM, and TV, as well as Travelers Information (TIS) stations. I have found the FCC information for US stations to be highly accurate. Be wary of Canadian and Mexican information. Much of it is either redundant or out of date. Properly used, the FCC AM Query will output a large text file of all MW stations.

Opening the web page and selecting the dropdown boxes, "Authorization type: Licensed Records Only (Daytime + Nighttime" and "Output-- AM Short List (or AM List)", then clicking the Submit Data button returns a huge list of active stations. Save this to a file, print it, and you have the entire US mediumwave listing. But it is huge, some 8 megabytes in some cases. You can also search by frequency or state, thus you can create customized lists, saving and printing them.

The FCC also makes antenna pattern plots available. Virtually all stations with multiple towers have directional patterns and the FCC makes this plot available in .PDF form. Once displayed in your browser, this .PDF can be saved to a file for future reference. Pull up the page for the station of interest to get to the pattern link. Example: WWKB-1520 facility and WWKB-1520 pattern.

radio-locator.com, a favorite site of mine, also has an advanced station search page. Many of us think of radio-locator only as the site that shows us mediumwave antenna pattern plots. The great thing about their page is you can also plug in parameters to filter stations by frequency or state. You can even search by broadcast format. Results are returned in formatted HTML pages. Save the resultant pages to file, print them, and create your own database of stations.

As just stated, radio-locator.com is another site which produces antenna pattern plots. These particular plots depict the expected signal coverage area of the mediumwave station over a map. The pattern plot is displayed as a .GIF image. Once displayed in your browser, this .GIF can be also saved to a file for future reference. Example: WWKB-1520 pattern.

am-dx.com is a simple textual site that tallies all US stations by frequency. Canada and Mexico are also available. Pick a frequency, display the list, save it, then print it.

The AM Logbook by Lee Freshwater is another interesting site that lists stations in a myriad of ways. Frequency, call sign, state, city, sites (transmitter), slogan, etc. Again, select your preference, display the list, save it, then print it. US and Canadian stations are represented.

AM Logbook also provides its current AM database in spreadsheet (XCEL) format. You must of course have an XCEL (.xls) viewer. You'll find the link on the Updates page.

Topaz Designs is a basic textual site with search box, returning results by frequency, state, power cutoff (100W), and broadcast format. US and Canadian stations are represented.

Mediumwave List is a comprehensive site that offers a lot of information, including transmitter mapping, logbooks of users, and station news. Worldwide mediumwave stations are represented, including of course North America - Canada, Mexico, Cuba, the Caribbean, etc. To create your station list, look for the "MWLIST quick & easy" link on the home page. This site will also allow you to download files from their huge database of stations, by region or country. The output is in .PDF form. Registration is required for certain information beyond the basic.

Outside of the US, the Mexican government provides a very nice list of their mediumwave service in .PDF form. Australia provides a list of their mediumwave service in XCEL (.xls) form. Using the Industry Canada site, you can search the Canadian mediumwave service and create various lists in text, HTML, and XCEL form.

Note that most of these sites return station lists in a web page (HTML format) versus a simple text page. Lists can be saved as a web page by the Save As function in your browser. But there is also another way. It is possible to select the important data on the web page, copy it to the Windows clipboard (CTRL+C), then paste it into a text editor (CTRL-V). The text can then be saved as a text file, which may require a little editing. Sometimes it is easier to read this way. If you go this route, be sure to use a text editor that supports Unicode text format, like Window's Wordpad, Notepad++, etc. Window's Notepad does not, and you may get a jumble of text with no line breaks.

So, we have several options available for saving and/or printing station lists. We have two options available for saving and/or printing antenna pattern plots. If you choose to print some or all of these and place the pages in a binder of some sort, all well and good. But a comprehensive list of the entire US database is still a lot of paper to store, pack, and carry around. Of course we could just save all these files to a laptop and take the laptop with us. There is also one another option.

Next up: Mediumwave DX Meets the eReader

The Field Strength Machine

2011-07-22T09:29:00.004-04:00

What do professional broadcasters and the FCC use to measure the field strength of a mediumwave station? Let me assure you they don't use charts and graphs like we hobbyists do. Let's find out.

What appears to be the premium device on the market today for field strength measuring is the Potomac Instruments PI-4100 Medium Wave Field Strength Meter, available from Potomac Instruments of Frederick, MD, and shown in the photo just above. It is Potomac's "third generation of precision survey instrumentation intended for the direct measurement of electromagnetic field strength in the 520 KHz to 5.1 MHz frequency spectrum."

This meter has a laboratory quality radio frequency voltmeter, a calibrated, Balanced Loop antenna, an internal GPS receiver, an internal calibration source, and data acquisition hardware and software. The unit weighs in at about 5.5 lbs. It is the successor to the previous industry standard, the FIM-41 meter, also by Potomac.

Also included in the 4100 is a spectrum display. Sensitivity is phenomenal, from 22 µV/m (microvolts per meter) to 50,000 mV/m (millivolts per meter). And there is no "meter" as with old units; everything is indicated digitally and calibrated automatically. The on-board GPS indicates your current coordinates as well as the distance and bearing to the station. It even includes a "wet" compass. For more information, see the Radio World product survey.

Oh, what I wouldn't give to spend a day with one of these. What is the price, you ask?

A cool $14,975. You can pick up a used one for about $13,000. Or, you might be able to buy a second-hand FIM-41 for about $5,000, or rent such an older unit for $595 per week. I can only dream.

The older, Potomac Industries FIM-41 unit:

The Perfectly-Spaced Passive Loop

2011-07-11T05:17:00.001-04:00

Let's build a passive loop with perfectly spaced coil turns.

One of the problems I've always encountered in constructing passive loops is keeping the coil turns evenly spaced and perfectly parallel to each other. Regardless if you form a loop support in the form of a cross or a square, you must devise a way to space the turns evenly at each corner. Traditionally I would make the support of wood (usually 1 x 2 lumber) and file notches in the corners for the wire to sit into, or pound many tiny nails in a row to hold the wire apart. It's tough to file evenly-spaced notches very close together and tedious to pound a lot of tiny nails.

I tend to use light gauge insulated, solid copper wire for my loops. Stripped-out four conductor telephone wire is cheap and easy, usually running about 24 gauge. It's nice and light, flexible, and holds its shape. Have a walk around a hardware store and you will find many other items that might be used in the construction of antenna devices. One day, I came across some short plastic pipe nipples, generally used in sprinkling system work. These were 3/4 inch pipe size (3/4 inside diameter) and 1.5 inches long. They are threaded the entire way across, with thread spacing at 14 threads per inch (0.0714") apart - perfect thread spacing for this sized wire. The thread notch is just deep enough to accommodate most small sized wire. It would be difficult to file notches or drive tiny nails this precisely together. 1/2 inch diameter pipe nipples could also be used, as the thread spacing is the same.

I built a square frame for this loop, 24 inches on a side, again out of 1 x 2 inch wood, commonly called "furring strip". At each corner and at the center of each side I screwed a 2 inch screw (8 screws total) to hang the plastic pipe nipples on. One could probably use wooden pegs to avoid the metal screws being near the loop wires, but I have not found it a problem as it's a small amount of metal, and at 90 degrees to the wires. I placed a plastic nipple on each screw. The screws don't actually fasten the nipples down, but the nipples sort of pivot on each screw and move with the wire, settling where they need and taking up the wire tension. Use a screw with a wide enough head to capture the nipple so it doesn't slip off the screw.

The loop requires about 90 feet of wire, 11 full turns in all. I mounted a 365pf variable capacitor for tuning near one corner. Drive two very small nails into the frame at the same corner as the variable capacitor to secure the start and end of the coil. Fasten the wire to start and begin winding the loop, making sure the wire sits into each nipple thread from the thread closest to the frame and working towards the outside. Run the last leg of the final coil turn back to the ending nail and fasten there. Solder the start and end of the loop to the capacitor. Install a knob on the capacitor and you are done. This loop tunes precisely between 530 KHz and 1700 KHz.

PVC could be adapted to use as a frame, and I considered this before using the wood. A 3-legged, 3/4 inch PVC corner tee is available which has a female pipe thread at the center leg. The nipples would be screwed into this leg of each tee to form the corners of the loop like we did with the wooden frame. A PVC frame would be totally portable, as it could be disassembled very easily.

I find a loop with perfectly spaced turns to have sharper nulls and more precise (sharper) tuning. Try this loop sometime.

Silicon Labs Si4831 Chip and the Tecsun R-2010

2011-07-05T08:05:00.003-04:00

Many of us are anticipating the arrival of the new Tecsun R-2010 DSP radio. This radio will use the Silicon Labs Si4831/35-B30 chip, developed for consumer AM/SW and FM operation. This second generation mechanically-tuned digital CMOS AM/FM/SW radio receiver IC integrates the complete receiver function from antenna input to audio output into one chip, like the Tecsun PL-380's Si4734 digital chip did. The difference: this chip is analog-tuned.

Band coverage of the new chip is 504 KHz to 1750 KHz in the mediumwave band, 5.6 MHz to 22.0 MHz in the shortwave band, and 64 MHz to 109 MHz in the FM band. Note that the 120, 90, and 60 meter tropical bands are not available. Also note that the longwave band is not supported.

AM sensitivity is comparable to the Si4734 chip, at 30µV input for 26dB (S+N)/N (signal plus noise to noise). The PL-380's Si4734 chip had a typical 25µV (S+N)/N sensitivity.

The receiver IC has very low power consumption and runs off of two AAA batteries. Typical supply current at 2.7 to 3.6 volts input is 17ma. Shutdown mode (power off) requires an insignificant 10µa.

The main external components required are a 100K ohm tuning pot, LED tuning and power indicators, a ferrite loopstick antenna for mediumwave reception and telescoping whip for shortwave and FM. Again, similar to the Si4734 chip, the antenna ferrite inductance required will be 180-450 µH. The Si4831 also supports an air loop antenna for AM. Air core loop support is suggested through an external 1:5 transformer, raising the input inductance 25 times, allowing for an actual air loop inductance between 10 and 20µH. The PL-380's Si4734 chip also supported the air core loop in the same way.

No mention of soft-muting or user-selectable bandwidth filtering is found in the currently available Si4831 documentation. Surely this chip would have the capability of multiple bandwidths. In the documentation they describe "....patented architecture allows for high-precision filtering, offering excellent selectivity and SNR with minimum variation across the AM band." Selection of bandwidths on the Tecsun PL-380's chip was done by program code. Let's hope this one has the ability.

Frequency drift tests show perfection compared to a traditionally capacitance-tuned radio like the Sony ICF-C218 clock radio. Hot and cold tests performed (room temperature to 45C and room temperature to -10C) resulted in virtually zero drift.

As an added bonus, use of a mechanical resistive tuning pot allows the frequency to be displayed in a linear format on the dial, so frequencies at the high end of the band are not crammed together as with capacitive tuning.

The size of this unit is unknown to me, although it looks similar in format to the Tecsun R-9012 or the Kaito WRX911. Both of these units are cigarette pack-sized.

Silicon Labs recently reached a major milestone in the broadcast audio market, announcing that it has shipped its one billionth broadcast radio IC. Silicon Labs’ digital CMOS broadcast radios are widely used in handsets, portable media players (PMPs), personal navigation devices (PNDs), automotive infotainment systems, tabletop and bedside radios, portable radios, boom boxes and numerous other consumer electronics products.

Silicon Labs introduced the industry’s first single-chip FM receiver in 2005, the Si4700 IC. As the industry’s smallest, highest performance and most integrated FM broadcast radio IC, the Si4700 redefined how FM tuners were designed into consumer electronics products.

I eagerly await the introduction of the Tecsun R-2010.

Field Strength Calculations: Calculating

2011-06-25T08:39:00.007-04:00

As stated in the previous post, one more piece of information is required to complete the puzzle of calculating received field strength. That is the millivolt per meter level at 1 kilometer from the station transmitter, eminating in your direction. Notice I said "eminating in your direction". It is not good enough to simply calculate the mV/m level at 1 kilometer for the station's overall power output. Two things must be accounted for that change that result and would make our field strength calculation inaccurate. They are:

1. Antenna efficiency. A mediumwave tower or array of towers will be more or less efficient depending on their radiation length(s). The FCC provides us with a figure called RMS Theoretical for every station's antenna array whether it be one tower or several, measured in mV/m. Reflected in this figure is the efficiency.

2. Pattern gain. Multiple tower arrays inherently have broadcast patterns. Meaning, of course, they aim to broadcast a majority of their signal in a certain direction to cover their market audience and/or avoid co-channel interference with another station. Where you are in relation to that pattern is important. If you are in the major lobe of a 50KW station, it may be pumping upwards of 100KW towards you, or more. If you are in a sharp pattern null, it may only be beaming hundreds of watts towards you. The amount of millivolts per meter "facing you" is the important figure. The FCC provides that as well, in their pattern plots.

There is only one case where we will need to do a simple extra calculation to arrive at the full millivolt per meter level for a station. That is for stations with a single tower only. I will explain why in just a minute.

So let's put together what we need. First, pick a station within reasonable distance you think you'd like to log. Note its frequency. Next, gather the following four things:

1. The ground conductivity in mS/m between you and the station. Use the M3 conductivity map. If the station path crosses a couple of zones, estimate the average ground conductivity for the entire path. The resultant figure should fall between 0.1 mS/m and 30 mS/m, or possibly higher if part of the path is over salt seawater.

2. The Ground Wave Field Strength Versus Distance graph for the frequency of the station, one of the 20 graphs published by the FCC. Several frequencies are usually grouped into one graph. The graphs are in .PDF form. Have your .PDF viewer ready.

3. You will need to find your distance to the station in kilometers, and also the reverse bearing from the station back to you. Many calculators exist on the web which will compute this information. The FCC has a good one, be sure to check out their calculator. These calculators require you to know the latitude and longitude of both your location and the station's location.

www.wikimapia.org is a great way to determine your home latitude and longitude as it has a crosshair defining the center of the map, and thus the latitude and longitude. Move the map to your exact location and read the latitude-longitude in the web browser's address bar.

The station's latitude and longitude can be found in a couple of ways. The FCC's AM Query web page allows us to query the station by call sign. The search output will display basic information like latitude and longitude. Click on the call sign link and you will be taken to the FCC's web page for the facility (station). Example: WHAM-1180 page.

4. The last item. Get the millivolt per meter value at 1 kilometer from the station transmitter, headed your way. The method of locating this figure will depend on whether the station has one antenna tower or multiple towers in its array.

Determine if the station uses a single tower or multiple towers for the service you are interested in. This information can be found on the FCC's web page for the facility (station), as shown just above.

Note that stations may have more than one entry on the page, one for each service they operate under, i.e., UNLIMITED, DAYTIME, NIGHTTIME, CRITICAL HOURS. Be sure you are looking at the correct service. Sometimes stations use a different number of towers for day and night.

Multiple towers.

The mV/m figure is gotten from the pattern data. It's simple.

Multiple tower arrays will give you the option to display the pattern plot. The pattern plot link will be under a heading that looks like this:

Horizontal Pattern at 1 km radius (Sections 73.150 and 73.152):
Electric Field Strength pattern plot
Pattern Data for WXXI

Either link will give us the information we need, though the "Electric Field Strength pattern plot" gives a nice graphic pattern plot for the station. Click one of the links.

RMS Theoretical values, and in some cases RMS Standard or even RMS Augmented values will be displayed for each five degrees of compass, 0-360. Find the compass bearing that most closely matches the return bearing from the station to you. We need to record one value only. Preferably, record the RMS Augmented value, if given. If not available, record the RMS Standard value. If not given, record the RMS Theoretical value. These values are in millivolts per meter and are the value of signal level the station presents towards you.

A quick definition of RMS Standard and RMS Augmented values. RMS Standard is essentially the RMS Theoretical value plus 5%. It is a "guard" against interference to other co-channel stations by overstating the RMS Theoretical calculated value. If stations have pattern augmentations, and many do, the RMS Augmented field will be present. Augmentations are enhancements or detractions to the theoretical pattern.

I'll use WXXI-1370 for the example. At night it runs 4 towers and has a roughly figure-8 pattern north-south. WXXI's return bearing to me is 204.7 degrees. Checking the FCC pattern plot for the station, we see that the 205 degree return azimuth presents a facing RMS Theoretical of 350.59 mV/m and a facing RMS Standard of 368.88 mV/m. We will use the RMS Standard value in the final calculation.

Single tower.

A special case requiring a simple calculation. We will calculate the mV/m figure from the RMS Theoretical value.

Again go to the FCC's web page for the facility (station), as above. The RMS Theoretical value will be on this page.

Note again that stations may have more than one entry on the page, one for each service they operate under, i.e., UNLIMITED, DAYTIME, NIGHTTIME, CRITICAL HOURS. Be sure you are looking at the correct service. Sometimes stations use a different number of towers for day and night.

The FCC computes all RMS Theoretical values from a formula of course. The values are calculated for a distance of 1 kilometer. The FCC formula used generates accurate millivolt per meter values (as published) for multiple tower arrays. It is not accurate for single tower arrays, in that the mV/m value calculated in the single tower case always reflects a 1 KW output power. Hence, the only single tower stations having accurate, published 1 kilometer mV/m values are 1 KW stations. As an example, check the FCC's published figures for my local WHAM-1180 station out of Rochester, NY. This 50KW station shows a calculated RMS Theoretical value at 1 kilometer of only 376.59 mV/m. Now of course this cannot be correct for a 50KW station, as a 1 KW station running a quarter wave (.250 wavelength) monopole has an exact calculated figure of 305.768 mV/m at 1 kilometer.

376.59 mV/m would, however, be correct for a 1 KW station using the same single tower antenna that WHAM uses (a .492 wavelength antenna).

To accurately calculate the mV/m figure for WHAM (or any other single tower station), the following additional formula must be applied:

(Power in KW, distance in KM):

mV/m = RMSTheoretical x SQRoot(Power/Distance)

Thus in WHAM's case:

2662.89 = 376.59 * SQRoot(50/1)

WHAM's actual RMS Theoretical value is 2662.89 mV/m. And since it is a single tower antenna having an omnidirectional pattern, it presents this value of signal in all directions. Use the value you calculate for your single tower station of interest as the mV/m value that the station presents towards you.

Making The Calculation

Now we have all of our information. Let's get busy. We will use the FCC's Ground Wave Field Strength Versus Distance graph to arrive at the received mV/m signal level. Proceed with the following steps.

1. To make them universal, the FCC's Ground Wave Field Strength Versus Distance graphs are based on 100 mV/m levels at 1 kilometer. We simply need to calculate how many 100s our mV/m value is. Just move the decimal point left two places. In WHAM's case, 2662.89 mV/m, 26.6289 (26.6289 x 100 = 2662.89). The multiplier value we will use for WHAM is 26.6289. In WXXI's case, 368.88 mV/m, 3.6888 (3.6888 x 100 = 368.88). The multiplier value we will use for WXXI is 3.6888.

2. Find the station distance in kilometers on the graph, usually at the bottom. The bottom range is 10 to 1000 kilometers. The top range is 0.1 to 50 kilometers.

3. Draw a trace upwards (or downwards if using the top scale) until you hit the ground conductivity value curve that matches the average ground conductivity between you and the station.

4. From the previous point, draw a trace leftward to the scale on the left side of the graph. This is the base millivolt per meter level based on 100 mV/m at 1 kilometer. Multiply this value by your multiplier value. In WHAM's case, multiply times 26.6289. In WXXI's case, multiply times 3.6888. This resultant value is the received field strength in millivolts per meter at your location.

There you have it. You have ballparked the approximate field strength of your station of interest. If done correctly, you should find this in fairly good agreement with V-Soft's figure if you are near the zipcode point they based their calculation on. With a list of expected receive field strengths for various stations, you can judge the approximate sensitivity of your receiver. After a few times trying this, you will find the calculation to be rather simple to do.

Hope you have enjoyed this series.

Field Strength Calculations: Measurements

2011-06-23T09:25:00.010-04:00

Continuing on with ground conductivity, the higher the conductivity the farther away the station's signal will be copyable. Study the accompanying graph showing the range of a 600 KHz signal at the 50KW power level at various ground conductivities. 50 kilowatts over good ground conductivity of 15 mS/m will produce a very copyable signal at a distance of 375 kilometers (233 miles). At an average to poor ground conductivity of 4 mS/m, coverage is reduced to under 200 kilometers. Excellent ground conductivity of 30 mS/m takes the same signal out to more than 500 kilometers! A purely over-seawater path (5000 mS/m) should result in a fair signal out to about 750 kilometers or some 465 miles.

Also study the graph of the transmitter with only 1KW output at 600 KHz. It gets out quite well considering its output is a mere one-fiftieth of its bigger brother! Its range is perhaps a third of the 50KW transmitter.

Take another look at the M3 map from the previous part in this series. The country is filled with pockets of different ground conductivities, some large in area, some small. The mid-section of the country has some of the best. A large portion of eastern Colorado and western Kansas are in the 15 mS/m range. Most of Kansas proper is an incredible 30 mS/m. Signals propagating eastward out of Colorado travel a long way. Northern Texas and Oklahoma also have great ground conductivity.

Frequency of operation makes an important difference in how far a signal travels. Propagation distance at the high end of the mediumwave band is less than half the distance of that at the low end for the same received signal strength. A study of the two accompanying graphs comparing the distance coverage of 600 KHz, 1100 KHz, and 1600 KHz signals clearly show this.

The common unit used in measuring received field strength is volts per meter, or usually, millivolts per meter "mV/m". This is also the FCC requirement. An odd term, millivolts (thousandths of a volt) per meter. We all know what voltage is, but per meter of what, exactly?

Volts per meter expresses the voltage that would be induced in a one meter long wire placed parallel to the lines of flux of the received signal (remember the electrical flux from a mediumwave tower is vertical, the magnetic horizontal). This induced voltage results from the movement of the flux across the wire.

It is important to note that the E (electrical) component of an electromagnetic field is measured in a single dimension. Why? The intensity-versus-distance relation is a straight inverse rule, not the inverse square law commonly used for calculating received power density. In the perfect environment of space, if you double the distance the signal has to travel, the received voltage (in volts/meter or fraction thereof) is halved. Ten times farther away results in 1/10 of the voltage. This is known as field strength. Power density, a different method of measuring received signal strength, follows the inverse square law. That is, the density is related to the inverse of the square of the distance.

In broadcast parlance, millivolts per meter is often referred to in a different context, that being "dBu", or more accurately, dBµV/m. This is decibels above or below 1 millionth of a volt per meter. It is a convenient way to represent field strength, as the decibel is simply a ratio of values. Be sure not to confuse this dBu (lowercase "u") with the Greek "mu" ("µ") on the new model DSP ultralight radios. They are different. These radios actually measure dBµV - voltage across antenna terminals at a certain impedance, not volts per meter.

The FCC offers a conversion calculator to convert from dBu to mV/m and back.

Or, you can figure it yourself by using the following formula:

dBu = 20 * Log(mV/m * 1000)

To reverse the computation, converting dBu back to mV/m:

mV/m = (10 ^ (dBu / 20)) / 1000

But let's put received millivolts per meter into practical application, something a little more understandable. Hatfield & Dawson, Consulting Electrical Engineers out of Seattle, WA have a wealth of interesting mediumwave engineering documents for perusal, floating about the web. This document seems to describe it best in terms the layman can understand.

From an engineering report by Hatfield & Dawson, 2002:

"MW radio signal strengths are measured in volts per meter (V/m). The FCC requires that MW radio stations provide a predicted 5 mV/m daytime signal and a 5 mV/m nighttime signal or a Nighttime Interference Free (NIF) signal, whichever is greater, over the city of license."

"MW radio receivers vary greatly in sensitivity and much has been written lately about the poor performance of MW receivers built today. The general practice for broadcaster use for coverage is 2 mV/m for coverage in vehicles, 5 mV/m to 25 mV/m for in home and 25 mV/m in downtown office buildings. On a Walkman-type portable radio, you may need as much as 5 millivolts (5 mV/m) of signal to have static-free reception. The reason for these recommended signal levels is to overcome the effects of interference. Sources of interference include fluorescent lights, computers, TVs, office equipment, overhead power lines, and other appliances operating near a radio that can overload the receiver. In a city core, stations generally need more signal than this because of heavy attenuation inside large steel structures like office buildings. In your home, depending on the location, type of radio, and the utilization of any external antennas, you can have good reception with signals between 1 mV/m and 25 mV/m."

radio-locator.com produces widely used antenna pattern plots, available to interested parties over the web. These depict the expected signal coverage of the mediumwave station. radio-locator divides the signal coverage area into three distinct ranges.

1. Local (red line), the area in which the field strength is 2.5 mV/m or greater, where "....you should be able to receive the radio station on almost any radio with moderately good to very good reception".

2. Distant (purple line), the area between 0.5 and 2.5 mV/m, where "....the signal of the radio station may be weak unless you have a good car radio or a good stereo with a good antenna. You may not be able to receive the station at all on Walkmans or other portable radios".

3. Fringe (blue line), the area between 0.15 and 0.5 mV/m, where "....the station's signal will be very weak. You may be able to receive this station if you have a very good radio with a good antenna, but it's possible that interference from other stations may prevent you from picking up these stations at all." This seems to agree with Hatfield and Dawson's report.

Another important factor in our quest to predict received signal strength is transmitter antenna efficiency. Size does matter. The better the antenna, the better the station gets out. Returning again to Hatfield and Dawson, now discussing mediumwave antennas:

"MW antenna heights are referenced to a wavelength (this only includes the radiating portion of the tower). In MW broadcasting, 5/8 wavelength (or 225°) antennas are more efficient than ¼ wave antennas. A ¼ wavelength (or 90°) antenna is near the lower end of acceptable antenna heights. Antenna heights much below ¼ wavelength are undesirable, as efficiencies decrease dramatically below this height. A 225° antenna provides the maximum coverage and is the theoretical maximum. The efficiency decreases for antennas taller than 225°, which results in reduced coverage. In summary, taller towers are more efficient and shorter towers decrease coverage and are more difficult to work with."

So back to our quest of received signal strength prediction. Few documents are available which demonstrate how to predict "real-world" surface propagation distances at mediumwave frequencies. Many analysts use vanilla formulas for calculating free space path loss using the inverse square law, computing the path loss (in dB) from transmitter to receiver. The path loss, in turn, is used to determine the received field strength value.

Unfortunately, free space path loss assumes a perfect environment, like you would find out in space or over a perfectly conducting earth. Be wary of cute little field strength calculators on the web, their resultant field strength figures are almost an order of magnitude higher than what is seen in real life. Formulas exist which will predict field strength at mediumwave frequencies, but the math is well beyond the average person's ability.

A simpler method exists to ballpark the figure we want. We need but one more piece of information to complete the puzzle. That is the millivolt per meter level at one kilometer from the station transmitter, emanating in your direction. Using that with the FCC's Ground Wave Field Strength Versus Distance graphs and the M3 conductivity map we can estimate the received signal level in mV/m to fairly good accuracy at our location for any station.

The next part of this article will show you how to do that. But let me leave you with this before we go. What information can we derive from the FCC graphs and other station data to maximize our daytime DX distance?

1. The lower frequencies propagate better per unit of distance. Stations near the low end of the broadcast band propagate nearly three times farther than ones at the highest end, for the same power output and same ground conductivity. The lesson: listen to the lower end of the MW band if you want extreme distance in reception.

2. Look for over-water paths. A local example: Ground conductivity around here in the Rochester, NY area is about 8 or a little less, tending towards the 6 mS/m figure judging from reception experience. Without passive loop assistance, normal daytime reception limits seem to max out at about 150 miles. That is, except for two stations: WJR-760, Detroit, MI and CKLW-800, Windsor, Ontario, Canada, near Detroit. These two are out at about 250 miles or about 400 kilometers. Why are they receivable? Most of their signal path is across water over the east-west length of Lake Erie into Rochester. Reception is routine on most simple radios with medium or better sensitivity.

3. Study station antenna patterns. The FCC web site is great for this. Virtually all stations with multiple towers have directional patterns and the FCC makes the pattern plot available in .PDF form. Study the plot and pay particular attention to your azimuth away from the station. Pick stations that push a lot of signal in your direction. They are the best prospects. Example: WXXI-1370 pattern

4. The radio-locator "fringe" 0.15 mV/m boundary seen on their plots is just that - fringe. Many stations are copyable at this boundary and beyond on a sensitive radio. Don't hesitate to try for them. Example: Denver stations KHOW-630 (only 5KW), KKZN-760 (50KW), and KOA-850 (50KW) all have excellent strength east to well past Hays, Kansas (300+ miles, or 483+ km) despite the fringe zone ending miles back towards the Kansas/Colorado state line.

The jury seems to be out on how far ground conductivity plays a role in daytime propagation. Some documents refer to the 55 kilometer figure, others to 150 kilometers. My bet is it is well beyond the 150 km figure as I have routinely heard stations at the 800 kilometer range during high daylight hours at all times of the year.

Next up: Calculating

Field Strength Calculations: Ground Conductivity

2011-06-20T08:26:00.009-04:00

Ground (also called soil) conductivity plays a huge role in how far the mediumwave signal travels during the daytime. Lesser known to many, station frequency is also a factor, and maybe more of one than you would think. Though one can argue successfully that frequency is not a factor in the formula for calculating received signal strength, it indeed becomes relevant as you will see. In this series, let's explore ground conductivity and station frequency and see how they relate to "how far you can hear" on the mediumwave band during the daytime. We will end with a method to calculate approximate field strength for stations of interest.

Many years ago, ground conductivity measurements were compiled into a map titled "Estimated Effective Ground Conductivity in the United States" (Figure M3) by the FCC. This map is used for the allocations planning for placement of MW stations in the United States. The map presents optimistic ground conductivities and is used when measured conductivity is not available. This information has been used and accepted since it was compiled in 1954.

Soil conductance is measured in siemens per meter but most generally shown in millisiemens per meter. This is the mS/m designation you see in the accompanying chart. The siemens (symbolized S) is the Standard International (SI) unit of electrical conductance. The old term for this unit is the mho (ohm spelled backwards). Conductance (mho) is of course the opposite of resistance (ohm). As you can see, salt sea water provides the best conductance by far (5000 mS/m). The higher the value the better. Average soil runs 6-8 mS/m. Find your location on the map and see what your local conductance value is. Notice also that a distant station's receive path may transition across more than one zone.

Equally important, the FCC also produces a series of charts known as the "Ground Wave Field Strength Versus Distance" graphs. These 20 graphs in .PDF form are grouped by mediumwave channels in the 540-1700 KHz range, and allow prediction of received signal strength by cross-referencing the distance to the receiving location with the ground conductivity factor between you and the station. These charts cover soil conductivity ranges of 0.1 mS/m to 5000 mS/m. They are still in use today. The only working link I have for them is:

FCC Ground Wave Field Strength Versus Distance Graphs

Be sure to get the .PDF versions.

How well a mediumwave transmitter "gets out" is not only dependent on its power, frequency, and the ground conductivity between it and you, but also on the ground condition at its location. The following is a quote from the Standards of Good Engineering Practice Concerning Standard Broadcast Stations (550-1600 kc.), 1939, and is still relevant today:

"The ideal location of a broadcast transmitter is in a low area of marshy or 'crawfishy' soil or area, which is damp the maximum percentage of time and from which a clear view over the entire center of population may be had... The type and condition of the soil or earth immediately around a site is very important. Important, to an equal extent, is the soil or earth between the site and the principal area to be served. Sandy soil is considered the worst type, with glacial deposits and mineral-ore areas next. Alluvial, marshy areas and salt-water bogs have been found to have the least absorption of the signal."

All well and good. Our transmitter is well-located, emitting a good signal traveling over perhaps many kilometers or miles to our receiving location. We either hear it or we don't depending on the natural attenuation decay between us and the transmitter. But just how do we predict the outcome? How do we (abstractly) measure a mediumwave signal's strength at the receiving end? We will use these tools and others to find out.

Next up: Measurements

Signal Patterns - 670 KHz - American Southwest

2011-06-10T10:38:00.005-04:00

Though I am back in New York for the summer, lets temporarily time travel back to the southwestern United States to January of this year. This article was written then but never posted.

January, 2011. Southwestern Arizona.

The Players:

KIRN-670 Simi Valley, CA 5KW 260.6mi
KMZQ-670 Las Vegas, NV 30KW 197.9mi
KBOI-670 Boise, ID 50KW 683.6mi
KLTT-670 Commerce City, CO 50KW 681.0mi

In the hour just after sunrise this time of year, little KIRN-670, Simi Valley, CA (5KW at 260.6 miles) is sometimes audible here, fading in and out weakly amongst a handful of stations. An ethnic station, KIRN (K-IRAN) plays a wonderful selection of Iranian music. KIRN has three main competitors at this time of day. The strongest and main signal heard during this hour is news-talk KBOI-670, Boise, ID (50KW at 683.6 miles). Weaker, though closer to me is Las Vegas, NV station KMZQ-670 (30KW at 197.9 miles), usually down in the mud for some reason. Last, christian affiliate KLTT-670 in suburban Denver's Commerce City (50KW at 681.0 miles) has already peaked about an hour before and is fading away for good as the sun heads west. Or is it?

KBOI in Boise disappears for good about one hour after sunrise. Then follows KIRN, farther west. As high-daylight emerges, left on frequency seems to be KMZQ in Las Vegas - weak, but audible throughout the day on a sensitive radio like a Sony 2010. KMZQ's pattern is directed mostly northwest (335 degrees), so most of its signal is funneled away from my location approximately four hours south of Las Vegas. It is sometimes weakly audible at certain times of day on the truck radio, a somewhat sensitive beast. Without an assist, most ULRs offer up only noise on this channel during daytime hours.

My loop of choice, a 24-inch passive loop, does wonders during the day. KMZQ-670 becomes clearly audible at medium strength on any radio. Rotate the loop a little to the east, and surprisingly Colorado's KLTT-670 is often present at varying ultra-weak to weak signal strength. KMZQ-670 is always in there, though. KLTT sometimes rises above and is nearly in the clear with proper nulling, particularly late in the morning. KLTT is an excellent DX catch here during daylight hours - at an astounding distance of 681 miles. Helping tremendously is KLTT's signal pattern. I am in the main lobe of its daytime pattern, which points roughly southwest (247 degrees). A resounding 5.0 dB pattern gain results in 161 kilowatts ERP being pumped this way after sunrise, crossing the high continental divide running through the center of Colorado. So far, KLTT-670 is my Arizona fixed location distance record for daytime DX. Two other personal records of longer distance are documented in a previous article.

Returning to 50KW outlet KBOI-670 in Boise, if we can receive 50KW KLTT-670 in Denver at 681 miles during daylight hours, why can't we receive KBOI at 683 miles? So far this station has only been audible during nighttime hours. Part of the problem here is KBOI's pattern. During the daytime, it is an omnidirectional one without gain. Secondly, and unfortunately, Las Vegas's KMZQ is also almost directly in-between KBOI and me. Null KMZQ, and I am nulling KBOI. Daytime reception will probably never happen.

Still I listen for little KIRN-670 over in Simi Valley. I have not caught it during daytime hours yet, but continue to try. The possibility exists that its 5KW signal could one day make the grade over the relatively short distance of only 260 miles. KMZQ in Las Vegas is a major problem, though. Little azimuth exists between these two stations from this location, making it hard to null KMZQ effectively enough to quiet the frequency. It is interesting that KLTT makes the grade all the way from Denver over the 681 mile path at 50KW, but KIRN cannot manage 260 miles with 5KW. Partly, KIRN's pattern is due south, and I am off the side of it. The return pattern loss is a negative 5.5 dB, so only 1384 effective watts are sent this way.

It would be nice to one day hear Chicago's 50KW WSCR-670, at 1530 miles distance from southwestern Arizona. It is on a bearing of 60 degrees, slightly east of Colorado's KLTT at 47 degrees. Looking at a grayline map, it might be possible to snatch WSCR at its local sunrise time, as KLTT is still at low power for the darkness period (at 700 watts), and Las Vegas's KMZQ is still at low power as well (600 watts). Evenings may be possible too. On another channel, WWL-870 in New Orleans is receivable here at 1437 miles many evenings, though it has less competition.

Check out the pattern plot for KMZQ. See how nicely KMZQ avoids KIRN and KLTT, fitting them exactly into the deepest nulls of its pattern. Nice work!

The Mystery Of The Missing Sunspots - Solved

2011-06-04T09:51:00.000-04:00

The long dry-spell explained by NASA. One of the mysteries of the erratic nature of sunspot cycles has finally been solved. Back at the last solar minimum, sunspots virtually disappeared for a two year period - 2008 and 2009. Many wondered if they would ever return.

In March an article appeared in NASA Science News explaining the inter-relationship of previously-known solar plasma flows ("meridional flows"), plasma flowing in a constant loop from the surface of the sun, diving to the interior at the poles, then reemerging at the equator of the sun in a constant symphony of motion.

"Plasma currents deep inside the sun interfered with the formation of sunspots and prolonged solar minimum," says lead author Dibyendu Nandi of the Indian Institute of Science Education and Research in Kolkata. "Our conclusions are based on a new computer model of the sun's interior." Read more in this fascinating article, Researchers Crack The Mystery Of The Missing Sunspots. Maybe we are on the verge of being able to predict the length and intensity of solar cycles?

Spring 2011 DX Notes - Denver To Rochester

2011-05-29T14:54:00.005-04:00

Better get the trip caught up so we can move on. We are continuing on across country to New York from Denver. The majority of the reception reports below are daytime loggings, as usual. Local times are noted. Radio is a 2006 Ford Ranger truck radio with extended antenna.

Let me explain. One of the things I did in Denver was to check into the local hobby shop and buy a 36 inch piece of flexible, stainless steel music wire. This I attached to the truck whip antenna, extending it some 30 inches. It improves reception enough to make a difference in marginal situations.

Monday April 18

So, Monday morning about 8:30AM I start out of Denver headed east to New York. The route is I-70. Approaching Kansas, I begin to wonder if I will have a repeat of last year's fantastic daytime DXing experience crossing the high plains of Kansas and Missouri over to the Mississippi River. In that story, you may recall that I logged my best daytime distance record of 827 miles, that being the reception of KKZN-760 (50KW) Denver, Colorado in Pocahontas, Illinois in mid-afternoon, some 36 miles east of the Mississippi River. KGAB-650 (at only 8.5KW!!) Cheyenne, Wyoming was perhaps the better catch that day, logged just as I crossed the Mississippi River at 791 miles.

At 1158L passing mile marker 14 in western Kansas, I log a weak KGNC-710 (10KW) out of Amarillo, TX, at a distance of 241 miles. A weaker station is underneath, perhaps KCMO-710 (10KW) Kansas City, MO at 393 miles, or KNUS-710 (5KW) Denver, CO at 177 miles. Interesting reception, as Amarillo's KGNC's pattern is pointed almost due south and away from me. I am in the exact null of Denver's KNUS and off the side of Kansas City's KCMO.

Somewhere in the next few miles, I pass into Central Daylight Savings Time, crossing the time zone.

At 1323L and mile marker 35, sports station WWLS-640 (5KW), Moore, OK becomes apparent. She is weak, but readable, at a distance of 332 miles.

Five miles further along at mile marker 40, I tune to 690 KHz and catch little Pueblo, CO station KWRP-690 (250W) at 1328L and 193 miles distant. KWRP operates with a single tower, so we have no extra help from pattern gain here. A great catch for this low power and distance.

KXXX-790 (5KW), Colby, KS, just down the road, booms in. It has a good selection of country music.

At 1450L, approaching Wakeeney, KS, near mile marker 125, sports station WHB-810 (50KW) out of Kansas City presents a good signal. This, at a distance of 284 miles to the east.

At Hays, KS, I stop for the night. Like last year, Denver's KHOW-630 (5KW) at 306 miles, KOA-850 (50KW) at 298 miles, and KKZN-760 (50KW) at 310 miles all present excellent signals into Hays. Tomorrow we shall see how far their signals continue on during the daylight hours.

Tuesday April 19

Up early and on the road, as is my custom. It is only 5AM. When on the road in the heartland of the US during pre-dawn early morning hours I always try to make a game out of hearing stations "coast-to-coast", that is, from all four sides of the country. I am not disappointed this morning. Between 0505L and 0548L I log the quad four: KFI-640, Los Angeles, CA, WCCO-830, Minneapolis, MN, WWL-870, New Orleans, LA, and WSB-750, Atlanta, GA. They are all 50KW powerhouse stations with varying signals this time of the morning. KFI-640 out of Los Angeles is the last to be heard at 0548L. She is weak.

At 0558L and still dark, I catch CBC-540 (CBK, Saskatchewan) with some nice Radio Australia programming. 961 miles, but easy nighttime reception. I am passing through Salina.

The sun is up, it is cold, and winter has made another spring appearance today. At 0649L I hear KWMT-540 (5KW), Ft. Dodge, IA at 299 miles. It is snowing, with several inches of snow on the ground already. The local conditions where I am are rain to misting rain. And a cold rain I might add.

Denver's KHOW-630, KOA-850, and KKZN-760 are nowhere to be found now that the sun is up. They will not be heard from again during daylight hours. Conditions are different this year.

Coming into Abilene, KS at 0705L, I log WJAG-780 (1KW) out of Norfolk, NE, at 214 miles. I've never come across this station before. Add another odd "W" in the log west of the Mississippi.

At 0715L, east of Abilene and parked on 790 KHz, I hear mention of "west Texas" from a very weak station. Could this be KFYO-790, Lubbock, TX (5KW)? It does not appear to be Colby, Kansas KXXX-790. Unknown. 462 miles if so. This would be excellent DX.

Forty miles west of St. Louis I stop for the night. Severe weather is about, in the form of hail and tornadoes. The tornado sirens have gone off to a packed Busch stadium, hosting some 40,000 fans to watch a St. Louis Cardinals game.

Wednesday April 20

Another cold, drizzly day. I am hearing WMT-600 (5KW) Cedar Rapids, IA all the way into St. Louis, across the Mississippi, and through southern Illinois and Indiana into Indianapolis nearing mid-day (319 miles). It fades east of Indianapolis.

Spent the night in Mansfield, Ohio, about 50 miles south of Cleveland.

Thursday, April 21

A quick six hour trip home.

Curious station placement in this part of the country is WYNE-1530 (1KW), North East, PA, and Buffalo, NY powerhouse station WWKB-1520 (50KW). Not only are they only 10 KHz apart in frequency, but they are also a scant 65 miles apart in distance along the I-90 corridor connecting Erie, PA and Buffalo. Cruising across I-90 through the northern tip of Pennsylvania, WNYE's 1KW signal is received very strongly. Parked on 1520 KHz trying to receive WWKB, at first I thought I had an IBOC station next door, with all the sideband splatter. I discovered WYNE runs AM stereo. I wondered if WYNE's close proximity to 1520 was the reason I couldn't hear blockbuster WWKB this close to Buffalo.

It wasn't until I got home to Rochester that I discovered why. Buffalo's WWKB-1520 puts almost zero signal into this part of northern Pennsylvania towards the towns of North East and Erie. The entire I-90 corridor running southwest out of Buffalo is in the deepest notch of WWKB's tower pattern. This notch is so good, that WWKB doesn't really even show up on the radio until you get within about 30 miles of Buffalo. Nice antenna work!

WYNE is operated by Mercyhurst North East College. The station is one of those rare stations authorized to operate during daylight hours only.

WYNE is also used as a teaching facility for Mercyhurst North East’s liberal arts/radio broadcasting associate degree program. Students learn everything from on-air broadcasting of news, sports and weather, to how to operate radio equipment, to advertising sales.

Arrived home early afternoon. Back to DXing from the east coast! More to come.

Spring 2011 DX Notes - Phoenix To Denver

2011-04-26T13:42:00.004-04:00

A trip across the country is always an enjoyable experience for a mediumwave radio DXer if he has a radio along. While on the road, traveling coast-to-coast presents many different DXing situations and opportunities to observe interesting propagation conditions.

Never being much of a nighttime driver, about 95% of my traveling is during daylight hours. This works out well for me since my particular radio passion is long distance daytime DXing. Cruising along at 70mph in a 2006 Ford Ranger pickup, radio on, tuning up and down the dial searching for weak stations at the lower end of the broadcast band where signals seem to propagate better - life is good.

I stewed about what route to take. Early April weather can be unpredictable and nasty in the high Rockies of Colorado. A trip through this area at this time of year can be tricky. This year I elected to avoid the possibility of extreme weather and travel the I-10 corridor from southwestern Arizona to Denver by way of Phoenix, Tucson, skirt along the Mexican border to Deming and Las Cruces, New Mexico, then parallel the front range of the Rockies northward by following I-25 via Albuquerque and Las Vegas, NM on in to Denver. This leg of the trip back to New York will cover some 1100 miles.

Wednesday April 6

Phoenix is a curious mediumwave city for its size. An unknown fact to many people, Phoenix is currently the 6th largest city in terms of population across the United States. In recent years it has regularly traded places with Philadelphia for positions five and six. As big as it is, both in population and physical area (a huge 517 square miles, 60+ miles across), Phoenix has only two 50,000 watt AM stations within a 25 mile radius of its center, and these are not even in Phoenix proper but in suburban Glendale and Tempe.

So, heading south on I-10 out of Phoenix, the lower powered Phoenix stations fade quickly. Tempe's 50KW powerhouse KMIK-1580 Radio Disney outlet seems to hold in there the longest. Approaching the north side of Tucson, some 100 miles distant, I start to hear some competition from another station on channel. They are broadcasting the Rush Limbaugh program. Confused I am, as my guide shows no other station on 1580 KHz near enough to cause interference. At the top of the noon hour when I hear the ID, the station turns out to be Tucson's conservative voice KNST-790 (5KW), being received strongly on its second harmonic of 1580 KHz! KNST's harmonic hangs in there all the way to the southern extent of Tucson, 20 miles from the transmitter site. I press onward towards the New Mexico border via Benson (north of Tombstone) and Willcox, through the lands of Cochise and the old Chiricahua Nation.

KFI-640 (50KW), Los Angeles is a mainstay of mine in southwestern Arizona during the winter. It is usually on at home or in the truck if I'm out running around. At 217 miles distant, it cannot be considered a local. But its signal is always there, and at good strength. I once heard KFI in mid-afternoon on this same truck radio from the Utah ghost town of Cisco, not far from Grand Junction, Colorado, some 594 miles distant! KFI gets out. Now at 1330L, cruising along I-10 in eastern Arizona and just east of Benson at mile marker 316, I tune for KFI. There it is, still in there but very weak. This, at a distance of 477 miles. KFI fades by mile marker 345, some 506 miles at this point, just past Willcox and only 50 miles shy of the New Mexico border. KFI transmits an omnidirectional signal with a single tower.

Perhaps the most remarkable station to put a daytime signal into southwestern Arizona during my winter stay is North Salt Lake City's sports-talk KALL-700 (50KW). It is receivable on this same truck radio during daytime hours with a weak to medium strength signal all day long. We are talking about a distance of 517 miles here, consistently. Between Benson and Willcox at 1334L, at mile marker 321 I tune for KALL. There it is at 617 miles, though very weak. I am only some 20 degrees off its four tower main lobe of 190 degrees. Understand, at this point, I am perhaps 40 miles north of the Mexican border hearing KALL's Salt Lake City, Utah signal. And during mid-day! KALL fades as I enter the western reaches of New Mexico.

At mile marker 352, ESPN's El Paso, TX station KROD-600 (5KW) is heard at 1405L with a respectable signal. This at a distance of 194 miles.

Crossing the border into New Mexico at 1445L, I tune to 850 KHz looking for powerhouse KOA (50KW) out of Denver. There it is, extremely weak and barely copyable. I have heard Denver radio twice during the daylight hours in southwestern Arizona in the form of KKZN-760 and KLTT-670 at extreme distances of nearly 700 miles, but never KOA. KOA makes the grade here at 554 miles.

Spent the night in Deming, NM, 30 miles north of the Mexican border. Tiny Columbus, NM, right on the border and just south of here, is the site of the famous Pancho Villa raid on the United States in 1916. Excepting the 9-11 attack, it is the only time the continental U.S. has been invaded by a foreign power.

Thursday April 7

Out of Deming the next morning I elect to take the shortcut around Las Cruces. State highway 26 juts off to the northeast, bringing me out to Hatch, NM, and I-25 about 40 miles north of Las Cruces. I am now heading northbound. Approaching Truth or Consequences, the only town named for a TV game show, I hear XEJUA-640, Milenio Radio, Juarez, Mexico, advertized at 500 watts and with a good signal. Juarez is just across the border from El Paso, TX, and due south of me right now at a distance of about 105 miles.

Albuquerque flies by with hardly a blink. Notable and famous in this part of the country is The Talk Monster, KKOB-770 (50KW). With a passive loop assist, it is weakly receivable in southwestern Arizona at 446 miles. For some reason, during daylight hours it seems to propagate better to the west than other directions, as this station basically disappears off the dial in Denver and points north and east. It seems odd that an omnidirectional tower would propagate differently in different directions. KKOB does run two towers at night, with its main lobe to the southwest at 248 degrees. Interestingly, KKOB is one of those rare stations running a synchronized repeater station for signal "fill in". The repeater, also using call letters KKOB, is in Santa Fe, NM, the next fair-sized town just north of Albuquerque. However, the distance between the repeater station up in Santa Fe and KKOB-Albuquerque is only 48.9 miles. Odd, it seems to me, that they need a repeater to fill in at such a close distance, considering KKOB's 50,000 watt signal blankets such a wide area around Albuquerque. I cannot detect KKOB's 230 watt repeater signal as I go by Santa Fe. As far as I know, I am still locked on to the main signal out of Albuquerque.

Proceeding north, at 1429L and 40 miles south of Las Vegas, NM, I find Denver's KHOW-630 (5KW) with weak signal strength at 304 miles. I am only about 12 degrees off of KHOW's main lobe at 200 degrees.

All the way from Deming, through Albuquerque, right up to Las Vegas I have been following El Paso's KTSM-690 (10KW) with good signal strength. At 1501L, arriving at Las Vegas, KTSM's strength at 258 miles is starting to fade. No matter, Las Vegas's own KNMX-540 (5KW) is overloading my radio. The station sits just east of I-25 with a two tower array. The main lobe pushes the power towards 341 degrees, across I-25 and over the north part of the town. Time to rest for the night.

Friday April 8

KNMX-540's overload lessens as I leave Las Vegas, and KTSM-690, El Paso, TX fades out totally a few more miles north, giving way to an unidentified oldies station which grows stronger as I near the Colorado state line at Raton, NM. This undoubtedly is Pueblo, Colorado station KWRP-690 which does run the oldies format. A remarkable signal for a distance of 190 miles, KWRP runs only 250 watts during the daytime. KHOW-630 still at 299 miles and KOA-850 at 272 miles continue to improve as I approach Denver.

The southwest is a wonderful place to DX on the radio. Wide, open spaces with few stations assure excellent long distance DX, even in the daytime. If you're ever crossing the country at some time, give it a try. There is no special equipment needed but an in-car radio.

Eastward Bound Once Again

2011-04-06T10:02:00.003-04:00

It's that time of year again. Winter is over and it's time to vacate Arizona's deserts and head back to New York for the summer. The projected route is Phoenix-Tucson-Deming-Las Cruces-Albuquerque-Denver - then points east - probably via I-70 or I-80. Will try to do some DXing along the way. No, of course I will do some DXing!

I apologize that a solid month has elapsed without an article. Life and work sometimes get in the way. Though no posts, I have been busy with radio endeavors. In my spare time I've been working on the Radio Data MW program some. Several articles are in various stages of completion and will be published soon. More in the Signal Patterns series are coming. An article on loop inductance calculations is in the works. I'm also working on an article on how multi-towered antenna array signal patterns are computed. Stay tuned.

Happy DXing!

The Vertically-Challenged Ferrite Loopstick

2011-03-02T20:59:00.008-05:00

As we saw in a previous article, An Unassuming Antenna, The Ferrite Loopstick, the groundwave signal decreases in strength when tilting the radio (and thus the ferrite antenna) towards vertical. This effects not just the station tuned to, but all signals across the mediumwave band because the pickup of the magnetic component is lessened when the ferrite rod or bar is rotated away from horizontal. During reception of nighttime, skywave signals, the effect is often less pronounced depending on atmospheric bending of the wave. So, how much is a signal reduced?

I decided to perform a static test. At mid-day I tuned my Sony 2010 to station KBLU-560 (1KW, omnidirectional) out of Yuma, AZ, 69.6 miles distant on a bearing of 200 degrees. KBLU is not a powerhouse here at this distance, but does present a lower-medium strength signal to a sensitive receiver. KBLU was arriving with a respectable 6-7 leds lit (out of 10) on the Sony. Rotating the 2010 to vertical reduced the signal to barely 2 leds. It was weak, but still copyable.

Next I fired up the Tecsun PL-380. Now, the PL-380 is an interesting receiver because it has a direct signal strength readout. KBLU, not as strong on this ULR, peaked at a strength of 25,07 (25 dBµV, 7 dB signal to noise ratio) during normal reception. Rotating the PL-380 to vertical reduced the signal to below the noise level at 15,00. There was no trace of KBLU in the headphones.

Another local, somewhat stronger station is KLPZ-1380 (2.5KW, omnidirectional) out of Parker, AZ, 33.5 miles distant on a bearing of 354 degrees. It registers 31,25 (31 dBµV, 25 dB signal to noise ratio) on the PL-380 during normal, peaked reception. Rotating the PL-380 to vertical reduced KLPZ's signal to a level of 16,06. It was still copyable, though very weak and just above the noise level.

On the Sony 2010, KLPZ registered a solid 7 leds when peaked in the normal horizontal position. However, when tilted vertically, the signal reduced to only a strong 2-3 leds. It was easily copyable. Overall, the Sony 2010 does not seem to do as good a nulling job as the PL-380 in the vertical position.

Similar results were had for the Sony SRF-M37V and Tecsun PL-600.

It was interesting to note that while in a vertical attitude, each radio could be spun about the vertical axis to a certain position causing a marginal improvement in the station's signal strength. This, proving some possible interaction with the radio's circuitry and the ferrite loopstick, or imbalance in the ferrite loopstick itself, causing some pattern skewing.

That the radio receives any signal at all while in the vertical position is interesting. At 90 degrees to the magnetic component there should be no magnetic component to receive on a local, groundwave signal! Again, skewing of the ferrite's receiving pattern might cause this, or perhaps a little magnetic component sneaking through due to path shift of the signal. Or perhaps the cause may be a curious effect usually attributed to open loop antennas known as "antenna effect", where the loop, if unbalanced, does in fact respond to and receive a small amount of the transmitted signal's electrical, or vertical component.

Nighttime reception using this technique is a mixed bag. Although mediumwave DXers routinely use tilting of a radio from horizontal towards vertical to help null distant pest stations at night, using the vertical technique to generally reduce the strength of all signals works erratically at best. Example: powerhouse KOA-850, Denver, CO was actually equal strength at times the other night in both the horizontal and vertical positions, at the same time! With skywave signals booming in from all directions and at many different angles due to atmospheric distortion of the wave polarization, you have your answer as to why.

Could this odd way of nulling signals be used to the benefit of the mediumwave DXer? Maybe at least during the daytime for those of us who are daytime DXers, when conditions are stable?

I set to wondering if it would be possible to nullify the radio loopstick's direct reception of signals while at the same time coupling a passive, external antenna device to the radio - all without tearing into the radio. This sounds counter-intuitive. Why would we want to reduce signal pickup of a radio's ferrite loopstick?

Passive antenna devices like loops and QStick-like devices are routinely used by mediumwave DXers to enhance signal pickup. The problem, and what bothers me the most about using these devices, is that the radio's own ferrite loopstick is still receiving contrary signals of its own at the same time, degrading the effect of the passive device. Further degradation may come from the radio's loopstick having poor nulling ability or an overly wide broadside peak, also compromising the purity of the passive antenna. The radio also might be positioned somewhat differently than the passive device, causing unwanted signals to interfere with the natural peak and null of the passive device.

So, the question remains: What if it were possible for the radio to only see the passive device as its antenna, and largely ignore directly-received signals from its own ferrite loop antenna? The vertically-held radio with its corresponding vertically-oriented ferrite loopstick seems to fill this bill. But how do we couple to it in this position?

This creates coupling problems in several respects. In the case of the external tunable ferrite loopstick or QStick device, it must be placed parallel to or off the end of the radio's own ferrite loopstick in order for it to work. That means it would be vertical too, and it wouldn't receive much signal itself, since when vertical it is 90 degrees to the magnetic component of the received wave just like the radio.

The usual passive loop, with its coil wound in a solenoid fashion on a square frame (sometimes called "depth-wound"), won't couple much signal at all to a radio held in the vertical position due to its loop being 90 degrees in relation to the radio's ferrite coil winding. If we rotate the passive loop to a horizontal position we have good inductive coupling to the radio, but then the passive loop is 90 degrees to the wave's magnetic component and signal pickup is reduced to nil. Perhaps a spiral-wound loop?

And another possibility becomes evident. Why not put the radio inside a Faraday cage, eliminating all outside signals? But then, how do we couple the passive device to it, and still not tear into the radio? All food for thought. Perhaps more in a future post.

Hope you have enjoyed this series on a most interesting device, the ferrite loopstick.

The Twin Coil Antenna Patent

2011-01-30T10:40:00.004-05:00

Let's continue our discussion of the ferrite loopstick, a most interesting device.

A curious animal appeared on the radio scene in March of 2003. It was called the Twin Coil Antenna. Its inventor was one Christopher Justice of the C. Crane Company.

A July 2001 application for United States Patent number 6529169, "Twin Coil Antenna", shows an "antenna for a radio receiver comprising a ferrite rod; spaced coils wound about the ferrite rod; a variable capacitor element connecting each coil together; and a combiner connecting each coil together." It was a souped-up ferrite loopstick.

In analyzing the standard tuned ferrite rod utilizing a single coil, Justice determined there is a "need for improved efficiency and a higher signal-to-noise ratio antenna that does not saturate at high frequencies", and it was to these ends that his experiments were directed.

Ferrite core antennas are widely used as antennas for radio receivers, particularly for AM broadcast band radios. This is done by winding a coil or loop, generally with tightly-spaced turns over one end of a ferrite rod or bar. The ferrite has the effect of concentrating and intensifying the received magnetic field inside the loop.

Unfortunately, the ferrite core tends to absorb some of the signal power. Additionally, the combined resistance or impedance of the antenna and ferrite core is typically just a few ohms or less. In operation, the antenna must be coupled to the larger input impedance of the receiver. This is generally accomplished by adding a capacitor to tune the ferrite loop to a certain frequency, creating a resonant circuit.

When a signal enters a ferrite rod antenna that is tuned to resonance with a coil and capacitor, the magnetic lines of flux begin to saturate. When this saturation occurs, the ferrite rod antenna takes on polarity, much like a magnet does. Ferrite antennas having only one pick-up coil result in loss of efficiency and limit the signal-to-noise ratio available to the receiver.

In the words of the patent application, "The invention provides an antenna for a radio receiver that has high efficiency, high signal-to-noise ratio and that does not saturate at high frequencies. This is accomplished by an antenna structure which employs a ferrite core having two (or more) coils coupled together and located on the ferrite core such that the magnetic fields coupled to the coils induce signals which combine to produce a resulting signal level equivalent to the combined signals in the coils. The coils may be coupled through a transformer where the combined signals of the coils are received in the primary of the transformer. The transformer coupling the antenna coils can dramatically narrow the bandwidth of the received signal. In addition, the antenna coils and the transformer windings may be connected to a capacitor to form a resonant circuit. The capacitor may be variable so the resonant frequency of the antenna may be set by tuning the capacitor. This results in an increased signal level and reduced interference and noise."

Read more about this fascinating antenna device on Google Documents' Twin Coil Ferrite AM Antenna. Justice's patent was accepted and issued on March 4, 2003.

CCrane sells their version of the Twin Coil Antenna on their website.

Next up in this series: The Vertically-Challenged Ferrite Loopstick

An Unassuming Antenna - The Ferrite Loopstick

2011-01-23T13:14:00.010-05:00

Ferrite core antennas, known as loopsticks, are widely used as antennas for radio receivers, particularly for AM broadcast band radios. This is done by winding a coil or loop, generally with tightly-spaced turns over one end of a ferrite rod or bar. The ferrite has the effect of concentrating and intensifying the received magnetic field inside the loop. Like other forms of loop antennas, loopstick antennas are relatively free from RF noise, as they react to the magnetic portion of the RF energy received and are relatively immune to the electrical component, which is prone to noise caused by electrical sources.

Radio waves have both an electrical component (E) and a magnetic component (H). They are 90 degrees in relation to each other and also 90 degrees out of phase. Looking at a signal eminating from a typical vertical AM broadcast tower, the groundwave electrical component (E) is vertical, or perpendicular to the ground like the tower, and the magnetic component (H) is horizontal, or parallel to the ground. Receiving antennas respond mostly to one component or the other: small, closed loop (less than 0.1 wavelength in wire length) antennas to the magnetic component, open-ended wire antennas and large, closed loop antennas to the electrical component.

Antenna polarization is defined by the orientation of the electrical component of the emitted signal. Since AM broadcasters transmit using a vertical antenna causing the electrical component to be vertical, the polarization is called vertical. The near-field wave polarization is vertical and the distant wave polarization generally remains the same out to the limits of the groundwave's propagation, normally 100-150 miles or more.

Since ferrite loopstick antennas respond mostly to the magnetic component of a radio wave, maximum groundwave signal pickup is when the radio is held in the horizontal, or usual position with the loopstick horizontal (parallel) to the ground.

Skywave signals, like those encountered from extremely distant stations during nighttime hours, can have an odd combination of the two polarizations (vertical and horizontal). Multi-path propagation may also be present, where the signal arrives and combines from two slightly different ionospheric directions.

Of course mediumwave DXers know that a ferrite loopstick has roughly a figure-8 pattern, with deep nulls off the ends of the ferrite stick. By rotating the radio with the end pointing to the station, the signal will null. By rotating the radio so the side faces the station, the signal will peak. Different radios, and different ferrite loopsticks, have different nulling and peaking qualities. Some have sharp peaks or nulls, some less defined. The nulls tend to be more pronounced than the peaks.

So, the following question begs an answer: What are we doing when we tilt the radio towards a vertical position, that is, causing the ferrite loopstick to rotate towards vertical - are we nulling the received signal, or just what?

For a groundwave signal, when tilting the radio towards vertical you are lessening the signal pickup of all stations, not just the station tuned to, by reducing the pickup of the magnetic component of all signals. This can be a bonus, sort of a novel way to reduce the RF gain on a receiver. Do you have a strong local that is giving you problems? Tilting the receiver towards vertical may be enough to reduce the overly-strong offending signal so that a weaker signal can be pulled through some distance away in frequency from the local. Just be aware that rotating a ferrite loopstick towards vertical effects all signals across the entire band, not just the signal tuned to.

During nighttime operation, when distant skywave signals may be arriving at slightly elevated angles of arrival or at skewed polarizations, tilting the radio may even increase signal pickup a little, and tend to reduce pickup of local stations.

The modern ferrite loopstick antenna, used in most handheld, portable, and even tabletop radios, is a marvel of antenna science. Measuring from perhaps a little more than an inch in length (as in the Sony SRF-M37V Walkman), to about 200mm (nearly 8 inches) in the large portables, its ferrite rod concentrates the received component of a mediumwave station's broadcast signal to produce such a respectable strength as to rival that of a wire antenna. Additionally, it is highly directional and infinitely steerable in all planes, all in a small enough package to hold in your hand.

Next up in this series: The Twin Coil Antenna Patent

New Years 2011 Mediumwave Daytime DX

2011-01-02T15:22:00.004-05:00

Haven't gotten the Sony 2010 out in awhile, so charged a fresh set of batteries and went on a little expedition out in the desert about 1300L yesterday. The sun was high, the temperatures cold for southwestern Arizona - 40 degrees during mid-day. I picked a nice hilltop site and commenced scanning some of the weaker channels. Along with me was a modified, spiral-wound 24-inch passive loop to aid in the DXing.

1315L KMZQ-670 Las Vegas, NV (30KW) 197.9 miles

KMZQ's three tower array has a pattern to the northwest, so pumps most of its signal away from me. Only about 12KW comes this way.

1327L KKOH-780 Reno, NV (50KW) 517.0 miles

Nice signal for this distance, strongly competing with KAZM-780 out of Sedona, AZ (5KW, 160.4 miles). KKOH runs a single tower with omni-directional pattern.

1334L KNWZ-970 Coachella, CA (5KW) 110.8 miles

KNWZ's three tower array has a pattern to the southwest, and I am in its null. Weak. Only about 1600 watts comes this way.

1347L KHQN-1480 Spanish Fork, UT (1KW) 464.7 miles

Weak, but a great catch for 1KW at that distance, the best of the day. KHQN runs a single tower with omni-directional pattern. Well under Phoenix's KPHX-1480 (5KW, 123.7 miles)

Early Mediumwave QSLs

2010-12-19T15:17:00.002-05:00

For many years radio hobbyists have collected QSLs, or verification cards and letters from stations they have heard. These items offer proof of reception of the station, and are often sent out by the station engineer upon receipt of a letter showing detailed reception information. Back in the 1920s when radio was the new rage across the country and people of all kinds were delighting in seeing how far they could hear, the EKKO Company of Chicago, Illinois, had a novel idea to produce reception verification stamps. Looking much like postage stamps - perforated, engraved, and in various colors - they were printed with station call letters, and EKKO even produced an album - selling for $1.75 - to paste them into. The reason? It was wonderful advertisement for EKKO's phonograph, record, and radio accessory products.

EKKO contracted the American Bank Note Company to produce the stamps, a company which already produced stamps for the US Post Office. The stamps for US stations framed the American bald eagle with two radio towers in the background. Stamps for Canadian stations substituted the beaver for the bald eagle. All stamps had a station bar below where the broadcast station call letters could be imprinted. EKKO's initials, E-K-K-O, were displayed on the four outer corners of the stamp. The stamps were purchased by the radio stations from the EKKO Company, and then, when their respective listeners provided written information identifying reception details of a particular broadcast, the station would send the listener a Verified Reception Stamp with the station's call letters.

The 1924 album marked the year when EKKO sold stamps to 592 stations in the United States and Canada, and at the height of the collecting craze they were selling their stamps simultaneously to more than 650 broadcast stations located throughout North America and the Caribbean! Independent research has identified over 844 stations that participated in the program between 1921 and 1929. These stations were located in the United States, Canada, Cuba and Mexico.

As the Great Depression settled upon America in the 1930s, the EKKO Company, like so many others, faded away as did the EKKO Verified Reception Stamp. Until recent years, the stamps have remained merely a curiosity among stamp collectors (called "Cinderellas"), but since 1980 interest in them has increased, and some have become quite valuable.

For more information on EKKO Verified Reception Stamps, see the following articles:

What's An EKKO Stamp?

Antique Radio

A 6-Inch Tunable Loopstick

2010-11-15T10:03:00.003-05:00

The homemade tunable loopstick device, similar to the Q-Stick by DXTools continues to be a popular article on RADIO-TIMETRAVELLER. Let's revisit this simple device and build another one, this time a 6-inch version.

Old transistor or table radios can be had for almost nothing at your local yard sale or flea market. I have reported on yard sales and flea markets before. Great radio values can be had from uninformed sellers.

Don't Laugh at Yard Sales
Another Deal, The Panasonic RF-565
Viva Flea Markets

I always keep my eye out for both working and non-working varieties, as the non-working ones can be stripped for their parts. Most important for building a tuning device: the variable capacitor and the ferrite loopstick.

The better buys are the radios having longer loopsticks or serviceable tuning capacitors. Many pocket radios are configured with the tuning knob directly connected to the capacitor, though the capacitor itself is often small in this case. Larger radio varieties often have a slide rule type dial mechanism, usually driving a more substantial capacitor. Surprisingly, most tuning capacitors in old radios, even the small ones, have 1/4 inch shafts, though short. So if the main tuning knob is intact and is one which is connected directly to the capacitor shaft, all the better. Save the knob.

This summer's flea market take was four old transistor radios. One was pocket sized, and the others were the type you would set on a desk, about the size of a small book. Three of the four had seen better days and did not even work. The other actually worked decently enough to keep and experiment with. Each cost two dollars or less.

The best loopstick of the bunch was a nice six inch one, a rod instead of a bar, wound very nicely with evenly-spaced turns of Litz wire to about 80 percent the full length of the stick. A short IF coil was at one end. I carefully removed the IF coil, as it is not needed.

I selected a small tuning capacitor which had a nice dial knob. At the end of the loopstick where there was room, I taped the capacitor to it by slotting the tape with a razor so it would fit over the shaft. The capacitor could also be hot glued to the rod if desired.

The coil wires were then carefully soldered to the center and edge terminals of the capacitor, forming the parallel tuned circuit. Be sure to use the edge terminal having the greatest capacitance, as the other one is the IF side of the capacitor with lesser capacitance. If you want to get fancy, you could enclose the loopstick device in a short length of PVC pipe, capping the coil end, and fastening the tuning capacitor on the other end of the pipe.

To use the loopstick, simply hold it parallel and near to the internal loop in your radio, then tune it to peak the signal your radio is tuned to. Rotate the two together, radio and loopstick, for maximum signal. The loopstick can also be rotated independently to null an offending co-channel station. A short length of wire or even a longwire could also be attached to one of the capacitor terminals, providing more signal, though it will lessen the directivity of the loopstick.

KDKA Turns 90 Years Old

2010-11-07T13:40:00.012-05:00

In 1920, Dr. Frank Conrad was an engineer in the employ of the Westinghouse Electric Company. He was also an amateur radio operator. With the release by Congress in July 1919 of all privately held radio and telephone equipment now that World War I had ended, the race to commercialize the new science of radio telephony was on.

To test transmissions during the war, Conrad placed one transmitter and receiver at the Westinghouse plant and another above his garage at home, four miles away. When the war ended and the government lifted the restrictions on amateur radio telephony, Conrad went back to his experimentation from home.

After the war, a fierce battle ensued between the US government and the Department of the Navy over control of the airwaves. The government won out and settled on the Department of Commerce to run things, wresting control from the Navy's hands. After the dust cleared, in April 1920, Conrad applied to the Department of Commerce to license his station. He was given the call letters 8XK.

Westinghouse saw that Conrad's experiments might be important and potentially profitable, and so with Conrad's help, started construction of a new transmitting facility on the roof of the Westinghouse plant in East Pittsburgh, PA. A presidential election campaign was in full progress that year, the election of 1920. The Republican ticket, comprised of Senator Warren G. Harding of Ohio and Governor Calvin Coolidge of Massachusetts was paired against the Democratic ticket's Governor James Cox of Ohio and former under secretary of the navy Franklin Delano Roosevelt.

On October 27, 1920, Westinghouse's radio facility was completed, and the Department of Commerce granted it the historic call sign KDKA. It transmitted on a frequency of 833 KHz (360 meters) with a power of 100 watts. Only two frequencies were assigned for broadcasting at this time. The other was 619 KHz (485 meters).

Hastily constructed, the "radio facility" was hardly more than a simple metal shack with all the necessary wires and equipment, and a desk from which an announcer could report election results. The election was slated for November 2.

On Tuesday, November 2, 1920, election night, up in that metal shack four men in dark suits compiled election returns received via wired-telephone from the newsroom at the Pittsburgh Post. The results were handed to one Leo H. Rosenburg. Leaning forward into an early microphone, Rosenburg's voice was sent through wires and apparatus out into the ether. It is estimated that between 500 and 1000 listeners heard this broadcast.

The excitement triggered by KDKA's 1920 election coverage set off a national hysteria for radio. Within weeks, Conrad had upped KDKA's power to 500 watts. It was now being heard as far away as Washington, D.C. Conrad started adding entertainment programs according to a schedule. Radio broadcasting, as we know it, was born.

Happy birthday KDKA-1020, Pittsburgh, PA, now 50,000 watts!

The Aeriola Senior regenerative radio.
Introduced December, 1921. $65.00

DXing From The Road, Fall 2010

2010-10-31T16:21:00.017-04:00

I am currently in southwestern Arizona after crossing the country from Rochester, New York in the last few days of September and the first part of October. Of course I did some mediumwave DXing along the way. The general route was I-90 to Cleveland, I-71 to Columbus, then I-70 all the way into Denver, cutting through St. Louis and Kansas City. From Denver I drove again via I-70 on to Moab, Utah, then south on US 191/163 through red rock canyon country across the Navajo reservation to Flagstaff, AZ, then on from there. Pictured is graveyarder KCPX-1490 (1KW) in Spanish Valley, Utah, ten miles south of Moab.

Here are some DXing highlights from the trip. Note that I did day-to-day checking on some regulars like KOA-850, Denver, and R. Enciclopedia-530, Havana, Cuba. Some may find this redundant; I find it is interesting to see how propagation changes in reception of these stations as you cross the country. Mileages are from the reception point indicated. Times are local (L). The Tecsun PL-380 was barefoot.

Monday, September 27.

First day out. Rain all day, and lots of highway construction, typical. On the truck radio, all across I-90 in northern Pennsylvania and Ohio, boomer KDKA-1020, Pittsburgh, PA (50KW) comes in quite nicely (about 100 miles distant). Best listening station in this area is WKTX-830 (1KW), Cortland, OH, daytime only. It is locally owned, proud of it, and plays a nice variety of old music, mostly 1950s. I wish there were more of these locally owned stations.

Stressed from the rain, I moteled it in Mansfield, Ohio, about 50 miles south of Cleveland. I found myself only one-half mile from Mansfield's own graveyarder WMAN-1400 (1KW). The PL-380 desensed a little on the nearby adjacent channels due to the big signal, but reception was not affected out past +/-30 KHz or so.

Tuesday, September 28. Mansfield, Ohio.

Same night, Monday night after midnight actually. I woke up just after midnight and decided to do a little motel DXing with the PL-380.

0015L WHLO-640, Akron, OH (500W). 51 miles.
0028L R. Rebelde-600, Cuba. Latest location info I have shows Holguin, Cuba, 1424 miles. Good signal.
0033L CIAO-530, Brampton, ON. 237 miles. East Indian music.
0043L WMOB-1360, Mobile, AL (212W). 760 miles. Good catch for low power.

Up again at 0515L, getting ready to hit the road. Raining hard. PL-380.

0531L R. Enciclopedia-530, Havana, Cuba. 1223 miles. Great signal.
0540L KVNS-1700, Brownsville, TX (880W). 1337 miles. Another good catch for low power.
0605L KOA-850, Denver, CO (50KW). 1173 miles.
0645L WTRU-830, Kernersville, NC (10KW). 340 miles. "The Truth", over WCCO-830, Minneapolis, MN.
0642L WGY-810, Schenectady, NY (50KW). 461 miles.

It is interesting to note that Cuba seems to always boom into Ohio (and Indiana). I have found this to be the case on all my trips through the midwest. Cuba is much weaker in Rochester, and seasonally sporatic when casually listening without the help of loops, etc.

By Tuesday night I make it all the way to High Hill, Missouri, a quiet exit off of I-70 with two motels and not much else, about 70 miles west of St. Louis. Noise level is low.

Wednesday, September 29. From the motel using the PL-380.

0402L CKDO-1580, Oshawa, ON (10KW). 737 miles.
0404L WZRX-1590, Jackson, MS (1KW). 456 miles.
0408L R. Enciclopedia-530, Havana, Cuba. About 1400 miles. Fair signal, not nearly as good a Ohio-Indiana.
0420L WCBS-880, New York, NY (50KW). 940 miles. Good signal.
0422L KOA-850, Denver, CO (50KW). 717 miles. Strong signal.
0429L WABC-770, New York, NY (50KW). 925 miles.

Wednesday afternoon, using the truck radio. I-70 mile marker 220, central Kansas. It is early afternoon and the sun is high in the sky. Denver is a still long way off, but I find Denver is making a strong daytime DX appearance already. I should have checked these stations 50 or 100 miles ago when I was closer to Kansas City.

KHOW-630 (5KW). 367.5 miles.
KKZN-760 (50KW). 370.0 miles.
KOA-850 (50KW). 356.1 miles.

The surprise here is little KHOW-630 with only 5 kilowatts, received at 367.5 miles. Its signal was better than KKZN-760's 50KW signal! This distance would be impossible during daytime hours on the east coast.

Wednesday night puts me into Hays, Kansas. From the motel using the PL-380.

2059L CBW-900 (CBC), Winnipeg, MB. 761 miles. Interesting interview with Ingrid Betancourt.
2106L WSM-650, Nashville, TN (50KW). 717 miles. Fair signal.
2110L KRSL-990 (30 watts), Russell, Kansas. 27 miles. Weak. Flea power. Much competition from a couple of other unknown stations. Interesting that 30 watts struggles over a distance of only 27 miles at night.

Thursday, September 30. Hays, Kansas. Still at the motel. PL-380.

0420L R. Enciclopedia-530, Havana, Cuba. 1480 miles. Weak.

No more DXing was noted until I hit Utah.

Thursday, October 7. From a desert campsite ten miles north of Moab, Utah. Reception approximately one hour before local sunset time. PL-380.

KKOH-780, Reno, NV (50KW). 541 miles.
WBBM-780, Chicago, IL (50KW). 1161 miles. Weak, under KKOH.
WSM-650, Nashville, TN (50KW). 1271 miles. Mixed with KMTI-650, Manti, UT.

Sunday, October 10. Three miles north of Mexican Hat, Utah. Mexican Hat is about as remote and far away as you can get from mediumwave outlets in this part of the southwest. The closest station is KVFC-740 in Cortez, CO, 73 miles distant, a little 1KW outlet. Big gun KTNN-660 (50KW), The Voice Of The Navajo Nation, is 96 miles, and its not-overpowering -95dBm strength is still heads and shoulders above any other station.

A mid-afternoon low bandscan (530 KHz - 1000 KHz) was done, using the PL-380.

1437L KLLV-550, Breen, CO (1.8KW). 97 miles.
1439L KTNN-660, Window Rock, AZ (50KW). 96 miles. The powerhouse.
1441L KOAL-750, Price, UT (10KW). 173 miles. Weak.
1441L KVFC-740, Cortez, CO (1KW). 73 miles.
1442L KHAC-880, Tse Bonito, NM (10KW). 115 miles. Weak.
1444L KNDN-960, Farmington, NM (5KW). 94 miles. "K-Indian" Navajo station with great country music.

That's it! Only a half a dozen stations could be heard between 530 and 1000 KHz. And about half of them were weak. Talk about a quiet band. Coupled to the 24-inch loop, many more stations were received. It is amazing how much extra signal even a 24-inch loop provides, making a dead band come to life.

It is interesting to bandscan with the PL-380 in such an extremely quiet location. The PL-380 has more whistles, strange whoops and heterodynes than I thought.

Hello Everybody! The Dawn Of American Radio

2010-09-22T05:17:00.005-04:00

It's that time of year once again when I'm getting ready to head cross country from New York to Arizona for the winter. One of the things I do is stockpile a bunch of books to read through the season. At the top of the radio reading list this year is a book entitled "Hello Everybody! The Dawn of American Radio", by Anthony Rudel. It is the story of the diverse entrepreneurial pioneers of radio, covering the era from 1912 through the 1920s and 1930s. Touching lightly on the technical aspects and inventors of radio, Rudel emphasizes the entrepreneurs and evangelists, hucksters and opportunists who saw the medium's true potential.

From Rudel's website:

"Long before the internet, another young technology was transformed--with help from a colorful collection of eccentrics and visionaries--into a mass medium with the power to connect millions of people.

When amateur enthusiasts began sending fuzzy signals from their garages and rooftops, radio broadcasting was born. Sensing the medium's potential, snake-oil salesmen and preachers took to the air, at once setting early standards for radio programming and making bedlam of the airwaves. Into the chaos stepped a young secretary of commerce, Herbert Hoover, whose passion for organization guided the technology's growth. When a charismatic bandleader named Rudy Vallee created the first on-air variety show and America elected its first true radio president, Franklin Delano Roosevelt, radio had arrived.

With clarity, humor, and an eye for outsized characters forgotten by polite history, Anthony Rudel tells the story of the boisterous years when radio took its place in the nation's living room and forever changed American politics, journalism, and entertainment."

It arrived yesterday and it promises to be a great read. Available from amazon.com and other booksellers. Published in 2008.

Signal Patterns

2010-09-18T11:35:00.017-04:00

Stephen from San Diego, CA, a reader of Mediumwave Oddities - Transmitter Power, wrote in with the following question:

"What stations actually are authorized with a HIGHER power at night than they are allowed in the daytime? I'll mention one - 760 KFMB San Diego, CA, about 7 miles from me. In the daytime they're only allowed a paltry 5KW omnidirectional, but at night they step up to 50KW."

An interesting question. And you mentioned signal patterns, all-important in the differences between daytime and nighttime mediumwave coverage.

I tweaked my database program Radio Data MW and came up with the following results:

73 US stations run higher power at night than during the day.

KFMB-760, your San Diego station, is the only one which runs 50KW at night and has a lower daytime power. KFMB uses one omnidirectional tower for daytime broadcasting. Power is set at 5KW during daytime broadcasting hours and 50KW at night. KFMB uses three towers at night to get that big 50KW signal out. But the pattern this time is pointed right out into the Pacific Ocean, to the southwest. San Diego's KFMB cardioid pattern has a deep, broad null at 60 degrees, nicely positioned for protection of Detroit Michigan's WJR-760 (50KW) and its western coverage area. Equally important, big gun KKZN-760, Thornton, CO (also 50KW), near Denver at 49 degrees is also protected, as well as a host of smaller US and Mexican stations.

KBRT-740 "K-Brite", a 10KW station in Avalon, on Santa Catalina Island is only a mere 85 miles to the northwest of San Diego's KFMB. It has a three tower array in use both day and night, pointing its signal due east to cover the Los Angeles and Long Beach areas, a scant 26 miles away. KBRT drops its power to a gasping 113 watts at night. Being nearly "co-channel" with KFMB at only 20 KHz removed, inspecting KFMB's pattern plot reveals that that the broad cardoid lobe to the northwest pumps an astonishing effective radiated power of 95KW up a 294 degree vector right at KBRT on Catalina. With a salt water path the whole way, that should be a lot of signal.

The next station with a big signal at night and a smaller one during the day is WLIB-1190 running 10KW daytime and 30KW nighttime, in New York, NY. WLIB uses three towers for daytime broadcasting and four towers at night. Both patterns are generally towards the east, with the nighttime pattern more focused and skewed a little more to the southeast. During the day it competes with WBIS-1190, Annapolis, MD (10KW), and WSDE-1190, Cobleskill, NY (1KW). WLIB's daytime pattern exactly bisects these two challengers on a line right out into the Atlantic Ocean. At night, WLIB only has to contend with New Yorker WSDE, as the Annapolis station is off the air.

The station with the greatest power differential, day to night, is WLAN-1390, Lancaster, PA. They run a mere 18 watts daytime and 1100 watts nighttime, both to a single, omnidirectional tower. Their nighttime power is a remarkable 61.1 times more than their daytime power!

WLAN's main competitor is WZHF-1390 (5KW), in Arlington, VA, a mere 92 miles away to the south-southwest. How does an 1100 watt station co-exist with a 5KW station at night when they are only 92 miles apart? Examining the tower pattern plots, you will find that WLAN in Lancaster, PA is exactly in a deep notch of WZHF's nighttime pattern.

Shown are nighttime pattern plots for San Diego's KFMB-760 and Avalon's KBRT-740, generated by Radio Data MW.

Winter DX Season 2010

2010-09-14T09:56:00.003-04:00

Great mediumwave conditions were apparent three mornings ago (September 11). I'm an early riser, and at 6AM I'm usually on the way to the coffee shop DXing on the truck radio. Of course at that time of the morning it's still very dark out. The sun doesn't rise here until 6:40L. Tuning to 850 KHz at the top of the hour news, I caught a nice full ID from 50KW KOA-850, Denver, CO (1420 miles) at 0605L. The KOA radiator, a single tower located 30 miles to the southeast in Parker, CO, is a skyscraping 667.9 ft. tall, almost a full 5/8 wavelength in height. As advertised, KOA gets out to some 38 states, and probably more. KOA began broadcasting in 1924.

Back in the late 1970s and early 1980s, I lived a mere 10 miles southeast of this transmitter, out in the rolling eastern plains of Colorado near the town of Elizabeth. I worked in Denver, and would drive past this tower every day (or night) on the way to and from work, often seeing mule deer or prong-horned antelope. Coming from the east, a long hill descended down appropriately-named Hilltop Road, ending at Colorado Highway 83 which ran past the tower. Headed to work one night for the graveyard shift during a blizzard, at midnight I remember becoming disoriented in the whiteout and losing control while descending that hill, shooting straight across highway 83 and through a barbed wire fence, coming to rest in the field right next to the KOA tower. Ah, memories.

KOA is a tough catch here in western New York with nighttime interference from sports stations WKGE-850, Johnstown, PA (10KW), at 199 miles, and WKNR-850, Cleveland, OH (4.7KW), at 235 miles. Interestingly, on my cross country trip each year I start to hear KOA at night consistently once I get west of Ohio and into Indiana, and under the 1200 mile distance range. I find there's something brick-wallish about that 1200 mile distance in mediumwave DXing.

WWL-870, New Orleans, LA (50KW), 1136 miles, is also appearing almost daily on the 6AM trip. WWL has a two tower antenna array, oriented south-north with major lobes to the northwest, and northeast. The northeast lobe points directly at me. Each of WWL's towers is a full 1/2 wavelength tall. With 3.3 dB gain in my direction, it pumps a healthy effective radiated power of 106KW right up a pipeline to New York. WWL's transmitters are located approximately 2 miles southwest of Estelle, LA, in the Jean Lafitte Preserve, a wetlands. All that water undoubtedly helps too. WWL has been in operation since 1922, predating KOA by two years.

Apparently the winter DX season is upon us once again.

Early Radio Publications

2010-08-28T10:38:00.004-04:00

This week I uncovered a treasure trove of early radio magazines in downloadable PDF format. If you love radio history like I do, you will enjoy browsing through these publications. Two magazines are represented.

Radio Broadcast Magazine, available issues from 1922 through 1930, covers in great detail the early years of broadcasting and includes much technical information for the early experimenter. The advertisements from these years alone are worth checking out. Articles in Radio Broadcast run the entire spectrum from MacMillan's expedition to the Arctic in the summer of 1926 to detailed descriptions of current vacuum tube circuit technology, projects for the amateur, to coverage and questions about governmental standards and practices in this early era of radio, to programming content and personalities. What a wealth of interesting information for the historian!

Radio Broadcast Magazine

Also available on this site is Radio Corporation of America's Radio Age Magazine, available issues from 1942 through 1957. This was a quarterly publication produced by RCA. A lot of interesting World War II coverage can be found during the war years, as well as new technology.

Radio Age Magazine

Be sure to check these out while they are still available.

Internet Radios

2010-08-24T09:30:00.004-04:00

I guess I'm too much of an old timer to get into this current Internet "radio" thing. Too many years spent toying with tuned circuits and antennas, too many years a radio DXer, radio listener, even a radio "Ham" - some 47 years - though I really haven't done the Ham thing for some time. WE7W lives on though, and I still keep my license current.

For better or for worse, sometimes words or things in life "evolve" over time to mean different things. I'm thinking radio is becoming one of them. Radio at one time meant "wireless" transmission of electromagnetic waves through the air, from starting point to finishing point. It was picked up magically with a wire or a coiled loop, fed to a tuned circuit which selected one signal out of many, detected and converted to audio which was then amplified so you could hear it. Internet "radio" is no such thing. No aerial, no tuned circuits, no detection. A friend of mine says real radio has to pass through your body (meaning: the waves) - that's the definition of real radio. I say that too, plus a tuned circuit must surely be involved, and almost certainly a detector. Internet "radio" has none of the above. What would Marconi think?

Internet radio probably is radio only in the sense that for a small segment of its "transmission" to you, millions of digital bits are perhaps beamed up to a satellite and back down. Maybe. The rest of its journey, both before and after, it is transmitted through wire or fiber optic cable, passed from one computer device to another to another, arriving in numerical perfection just as it was sent, down to the last, solitary, Boolean bit.

Merriam-Webster says about the noun RADIO:

a: the wireless transmission and reception of electric impulses or signals by means of electromagnetic wave.

b: the use of these waves for the wireless transmission of electric impulses into which sound is converted.

As I was saying: "waves", like the kind that pass through your body.

There was even a time when I used to subscribe to various radio magazines, until the articles became more computer articles than radio articles, each filled mostly with links to web sites. Recent shortwave magazine articles I've seen basically contain narrative on how to navigate a radio station's web site to get its streamed Internet content. Radio magazines have evolved to something different than they once were, too.

I just don't get it. There is no magic for me in Internet radio. See accompanying photo of toaster, er, I mean Internet radio. How about you?

Maybe it's the semantics of the whole thing that bothers me more than anything else. The new "radio" is not the old radio, and never will be. It is something wholly different.

Okay, a reality check. Yes, I do listen to a podcast now and then (now there's a new word unleashed on modern society for you: podcast), or streamed audio via my desktop or laptop. I've even been known to listen to a streamed radio station on occasion (try streamed KTNN-660 sometime, The Navajo Nation, 50KW out of Window Rock, AZ for an interesting experience). But the listening is done for "content", without the accompanied magic of original radio. There is no "feel" to it. I attempted to capture this feel in another post in this blog. I was talking about mediumwave towers:

...."A tower is a thing of beauty to the radio aficionado....Ah, the mediumwave broadcast tower! Think of it! Stately, striped sentinels with strobe lights flashing, they number thousands and thousands across the country, each emitting invisible waves of electrons through the late night air, spanning that mysterious thing called "the ether" to deliver communication to unknown distant masses. It conjures up thoughts of far-away points on the landscape, souls crouched in cramped corners with headsets fixed in the dark of night, straining to make sense of distant babble through static crashes and heterodynes. That would be me. The whistle of a far off freight train gives the same feeling of wonder."

Internet radio does not. Do you like your toast light or dark?

Mediumwave Oddities - Towers

2010-08-22T14:34:00.007-04:00

Today, we move on to tower oddities in the mediumwave broadcast band. Broadcast towers have always been an interesting subject to me. Did you see the news earlier this month on the WWVA-1170 towers collapse, due to severe storms in the Wheeling, WV area? The photo at left shows how they looked in the 1940s. WWVA-1170 started broadcasting in 1926.

Like last time, we will use data from current FCC records dated August 7, 2010. There are 4784 licensed stations in this survey. Previous posts in this series were Mediumwave Oddities - Transmitter Power and Mediumwave Oddities - Geography. Information has been gathered using the Radio Data MW program.

Again, daytime and nighttime data will differ. I will be explicit on which is which when the statistics are presented.

THE DAYTIME

Many mediumwave broadcast stations use multiple tower arrays to direct their signals towards intended markets, or away from other stations which they may cause inteference to. There are thousands of towers out there.

If we total all the towers of all the mediumwave stations transmitting in the daytime, how many would there be?

Answer: 7164. That's a lot of metal in the air.

Out of the 4784 licensed stations, how many stations have only one broadcast tower?

3569 stations have only one broadcast tower, which is 75% of all broadcast facilities. Surprisingly, the remaining 25% actually have more towers total than the single-towered 75%. Multi-towered stations average 2.95 towers per facility.

Essentially, a station with one broadcast tower has an omni-directional signal pattern, in other words, the station broadcasts with equal signal strength in all compass directions. Multiple tower arrays use phasing techniques to form skewed patterns of radiation, often in figure-eight or cardioid shapes. The lobes, or strong points of the pattern are directed towards market areas of interest. The nulls, or weak points of the pattern, are positioned toward areas to lessen interference with other stations or unwanted markets.

Back to tower counts, how many stations have two broadcast towers?

515, or 10.7 percent of the total have two towers.

How about three towers?

384, or 8 percent of the whole. The percentage drops dramatically off from there of course.

Which station has the most broadcast towers in use during daytime hours?

That would be KNTH-1070, Houston, Texas, with 11 towers. They are arranged in an odd grouping of three parallel rows of 3 each, with towers #10 and #11 jammed between the two rows. The rows head generally in a south to north direction. KNTH-1070 uses two less towers (9) during nighttime hours.

Are there more towers in daytime use east of St. Louis, Missouri, or west of St. Louis?

East of St. Louis, there are 4240 towers in use during daytime hours. 2924 towers are used west of St. Louis.

Radio station signal patterns are sometimes further modified at the tower site by what are called "augmentations". Augmentations are modifications to the standard broadcast signal pattern, usually to further null the signal strength in a certain direction to bring it into FCC "signal contour" compliance. An interesting discussion can be found on augmentation over at The Virtual Engineer AM forum.

Stations can have up to 28 augmentations to their signal pattern. This must be a technical nightmare for the broadcast engineer.

Which station has the most augmentations?

Four stations have 28 augmentations in use during daytime hours.

THE NIGHTTIME

Again, like we saw in Mediumwave Oddities - Transmitter Power, nighttime seems to be the more interesting as it has more odd variety.

How many total towers are used for broadcasting during nighttime hours?

Answer: 7877 towers. 713 more towers are used at night than during the day.

Being a mediumwave DXer, you know that signals travel much farther at night than during the day, commonly upwards of 1,000 miles and more. Stations often must follow different signal pattern guidelines at night to prevent interference to distant stations. This generally requires use of either a different tower arrangement or different number of towers, or both. Stations also may operate at reduced power at night.

Which station has the most broadcast towers in use during nighttime hours?

That would be KFXR-1190, Dallas, Texas, with 12 towers. They are arranged in two parallel rows of 6 each, heading from southeast to northwest. KFXR uses only 4 towers during daytime hours. Texas holds the record for stations with the most broadcast towers for both nighttime and daytime hours. They always do things in a big way in Texas.

Are there more towers in nighttime use east of St. Louis, Missouri, or west of St. Louis?

East of St. Louis, there are 4427 towers in use during nighttime hours. 3450 towers are used west of St. Louis.

Which station has the most augmentations?

Nine stations have 28 augmentations. Among them again is KFXR-1190, Dallas, Texas. I think KFXR-1190 should be considered for the record here. It is the station with the most towers (12) and tied with 8 others with the most augmentations.

I was thinking about ground radials this morning, which are the (generally) buried wires that are placed under broadcast towers to create the artificial ground that they operate over. Usually broadcast towers must have at least 90 quarter-wave length wires, and as many as 120 or more. Seeing as how we know the number of broadcast towers used in nighttime operation, the following question occurred to me:

If we assume 120 radials under each tower, how many total ground radials are in use?

Answer: 945,240. Almost a million radials.

Using an average length of 245 feet for each radial (a quarter wave length at 1000 KHz), how may feet of radials lie under mediumwave broadcast towers in the US?

231,583,800 feet. That is 43,860 miles of wire, enough to encircle the world almost two times. Time to buy stock in copper.

Hope you have enjoyed this series.

The WWVA-1170 towers after the August 4th, 2010 storm.

Australian Mediumwave Database

2010-08-18T11:01:00.003-04:00

I came upon an official Australian government link (ACMA - The Australian Communications and Media Authority ) the other day which documents licensed mediumwave stations for Australia in PDF format. Digging deeper, I found an official government database, published in EXCEL format. This file has the basic information, such as call sign, frequency, latitude, longitude, power, and service. No tower information is available, and only a crude maximum signal strength of the antenna pattern's maximum lobe is given. It is also a comprehensive file of all Australian transmitter data: MW, FM, and TV. None the less, it will be useful.

Using the EXCEL viewer, the mediumwave information can be copied in its entirety and saved as a text file. Further "massaging" can put it into a proper format. Then the information can be incorporated into a database of Australian mediumwave stations. The file is updated once per month.

List of licensed broadcasting transmitters (main page)

Broadcast transmitter data (EXCEL format)

Mediumwave stations, by call sign order (PDF)
Mediumwave stations, by frequency order (PDF)
Mediumwave stations, by area served (PDF)

Radio Station Databases 101

2010-08-17T13:11:00.025-04:00

Let's explore the details of some of the governmental mediumwave station databases available to us. Much information is there for the taking if you can extract it. But where do we find it? And how do we do that?

UNITED STATES

Although the FCC's AM Query provides a usable output of AM radio station information, the entire story is not told. Much technical information is left out, particularly field strength, tower, and other engineering data, information which can be found by digging deeper into the actual FCC database files. AM Query is simply a mechanism that extracts predetermined data from the real database, hidden in numerous files in the cellars of the FCC web site. These files are found in the FCC's Consolidated Database System (CDBS) electronic filing system. This database contains some very interesting and useful data.

CDBS file index via http site
CDBS file index via ftp site

I wanted more information than the FCC's AM Query could deliver. CDBS files document in detail the AM, FM, and TV (including digital) services, right down to measured signal strengths and distance between towers. Being an old programming hand for many years, some time ago the idea occurred to me to write a program which would use these files as input and provide a varied display of interesting and useful station data. My Radio Data MW program was born, and has become a sort of sideline hobby for me ever since. If I ever get it to a distributable state, I may one day publish it.

For the enthusiast or budding programmer wanting to extract information out of these files, where does he or she begin? Actually, once unzipped, all of these files are simple text files which can be opened in any text editor. My choice for a text editor in recent years has been Notepad++. It is an excellent freeware editor, useful not only for text files but also programming and scripting.

Okay, now that we have our text editor/viewer, how and where does one begin to gather information on mediumwave stations? From the CDBS database, here are the FCC files which must necessarily be examined. The pertinent information in each file is described. Be careful to note that these FCC files cover all services: AM, FM, and TV, including Traveler's Information Services.

The facility file, facility.zip (facility.dat)

This is the key file for unlocking all the others. There is one record here for each facility (station). The facility ID number within each record will eventually lead you to the rest. Keep it handy.

Information found in this file:

* The station's facility ID
* The station's service community city, state, and country
* The station's call sign
* The station's frequency
* The station's current licensing status
* The station's digital status (IBOC or not)

The engineering index file, am_eng_data.zip (am_eng_data.dat)

Multiple records usually exist for each facility. The application ID in each record points you to the station's antenna system record in am_ant_sys.dat. Keep this handy too.

Information found in this file:

* Cross reference back to facility ID
* The station's class (A, B, C, D, or unknown)
* The FCC application ID (an identifying number)

The application file, application.zip (application.dat)

This file contains a historical list of all applications filed by every station in the FCC database. It is a huge file, some 60MB.

Information found in this file:

* Cross reference back to facility ID
* The FCC application ID with cross reference to the more commonly known application resource number (BL-19990713DC)
* A secondary call sign reference (can be an old or new call sign)
* A secondary frequency reference (can be an old or new frequency)

The antenna system file, am_ant_sys.zip (am_ant_sys.dat)

Multiple records usually exist for each facility. An individual record exists for each service a station is authorized to use (Unlimited, Daytime, Nighttime, Critical Hours), and multiples of these may even exist. In this file we get to the heart of the station's information.

Information found in this file:

* Cross reference back to application ID
* The station's antenna system ID
* Number of augmentations to the signal pattern
* Hours of operation (its service: Unlimited, Daytime, Nighttime, Critical Hours)
* The station's latitude (tower site coordinates)
* The station's longitude (tower site coordinates)
* The station's power for this service
* RMS signal strengths at 1 kilometer in three varieties
* The station's domestic licensing status
* Number of towers
* Indicator showing if record is current or archived (important)

With a station's latitude and longitude, using proper programming it is possible to calculate its distance and bearing from your home location. It is also possible to calculate the sunrise and sunset times at the distant transmitter. Using the station power and/or measured signal strengths at 1 kilometer, and knowing the distance you are from the transmitter, the path loss and a rough relative received signal strength can be calculated for daytime reception of stations within a few hundred miles of your home location. Of course nighttime, with its enhanced signal propagation and atmospheric conditions, would preclude any calculated value.

The towers file, am_towers.zip (am_towers.dat)

In short, this file contains everything you need to calculate a station antenna's broadcast pattern. You can also plot tower positioning. A record exists for each tower in a station's tower array.

Information found in this file:

* Cross reference back to antenna system ID
* Antenna system resource number (ASRN - FAA number)
* Tower height, measured in various ways
* Signal field strengths
* Relative tower positioning
* Tower spacing
* Tower phasing

AM broadcast station signal pattern graphs are calculated through a rather complicated formula. A description of this and other formulas can be found at:

Directional Antenna Systems
Modification of directional antenna data

An excellent treatise on using these formulas can be found at:

A Modern Method Of Predicting AM Tower Vertical Radiation

The augmentations file, am_augs.zip (am_augs.dat)

This file documents the augmentations to the station's signal pattern. Multiple records can exist for each facility if augmentations are used. Radio station signal patterns are sometimes further modified at the tower site by what are called "augmentations". Augmentations are modifications to the standard broadcast signal pattern, usually to further null the signal strength in a certain direction to bring it into FCC "signal contour" compliance.

Information found in this file:

* Cross reference back to antenna system ID
* Azimuth of augmentation
* Span (in degrees) of augmentation
* Radiation strength of augmentation

Using this information, we can further refine a generated graph of the station's signal pattern.

The facility index, fac_party.zip (fac_party.dat)

This file is a simple cross reference of facility ID to owner information in the party.dat file.

Information found in this file:

* Cross reference back to facility ID
* Index forward to party ID (for owner information)

The owner information file, party.zip (party.dat)

A huge file of all kinds of owner information.

Information found in this file:

* Owner names and addresses indexed by party ID

And finally, to decode what all the above files mean, be sure to examine:

Code Table
Engineering Data Description (PDF)
readme.html

SOME EXAMPLES

Counting Licensed Stations

Have you ever seen the official FCC licensed station count? Lately the count has been 4786. The FCC uses the facility.dat file to determine this number. In this file, each facility has one line of information. There is a field in each line indicating the station's licensing status. Simply by totaling the number of LICEN (licensed) and LICSL (licensed but silent) entries gives you the licensed count. Total the LICSL entries by themselves, and you have a count of the number of licensed but silent stations.

Counting Digital (IBOC) Stations

Again, the the facility.dat file is used. A single character field in each record contains the letter "H" or "D" if a station is digital. Currently no "D", or purely digital mediumwave stations exist, they are all hybrid ("H") IBOC. Non-digital stations show a blank field. Count the number of "H"s, and you have the IBOC count.

Gathering It All

Combine the facility.dat file information with the engineering data index file information (am_eng_data.dat) and you know the station's class and most recent application ID. Look for this application ID in the antenna system file (am_ant_sys.dat) and you will have the station's position coordinates, hours of operation, and a host of other information. Cross reference the facility ID to the party.dat file and find the owner information. And finally, inspect the am_towers.dat file using the station's antenna system ID for the detailed field strength and tower information. Use the tower information and theoretical field strengths to calculate the antenna broadcast pattern.

Simple, it is not. It is overwhelming at first. The FCC's file layout is not friendly. But a tremendous wealth of information is available to the enthusiast or programmer who wants to work at it.

MEXICO

The FCC database has information on Mexican stations. Use it with caution. The two neighbor countries on our borders, Mexico and Canada, must file with the FCC for every station that wishes to broadcast. We do the same for them. Much of the data within is hopelessly outdated, especially the data for Canada, as Canada continually loses many of its mediumwave stations to the FM service.

The published link for official Mexican government mediumwave data is:

radio_AM.pdf

It is a PDF document of all supposed currently licensed and on the air mediumwave stations. All I have ever been able to get out of this link is a "503 - Service Temporarily Unavailable" response.

The next best bet comes from the official Mexican telecommunications site, Cofetel. The only government list I have found available, also in PDF form, is the Infraestructura de Estaciones de Radio AM list. Though the URL address is dated 2008, the actual PDF retrieved is dated 31-Dic-2009, or December 31, 2009, so hopefully the information is somewhat current.

Unfortunately, this station information lacks transmitter latitude and longitude coordinates, and a host of other needed technical information. It might be possible to correlate the Mexican stations with the FCC's database to get this. I haven't put forth the effort yet.

CANADA

Canada has a nice AM Query of their own, but like the FCC's AM Query, the entire story is not told and much technical information is left out. But we are in luck. It turns out that Canada's AM Query searches a deeper database just like the FCC does, so much of the information is available, though hidden.

The Industry Canada engineering database houses it, with links shown just below.

Industry Canada engineering page
Industry Canada engineering database (baserad.zip)

Rather than simple text files, Canada has chosen a dBase file format (.DBF) for its files. Download and unzip baserad.zip and you will have them. Though the records are somewhat textual in nature, they are more like EXCEL records and a text editor cannot be used to view them. You must use a specialized viewer in order to look inside.

CDBF for Windows by WhiteTown Software, which used to be available as a shareware DBF viewer/editor, seems now to be purchase only. I have the shareware version of it, and it is marvelous. Other DBF file viewers are available.

Once again we have our text editor/viewer, how and where does one gather information on Canadian mediumwave stations? From the Industry Canada database files, here are the ones which should be examined.

AMSTATIO.DBF

Information found in this file:

General AM station data, like the FCC's facility.dat file.

PARAMS.DBF

Information found in this file:

Tower info, like the FCC's am_ant_sys.dat and am_towers.dat files.

LOOKUP.DBF

Information found in this file:

Description of codes used.

CTRYDESC.DBF

Information found in this file:

Country codes

COMMENTS.DBF

Information found in this file:

Owner information

AUGMENT.DBF

Information found in this file:

Signal pattern augmentations, like the FCC's am_augs.dat file.

WRAP UP

Combining the Industry Canada information with the FCC's, we now have two countries with a wealth of information about their mediumwave service. If the missing information from Mexico's PDF file can be extracted from the FCC's database (namely the latitude and longitude coordinates of the stations), we can then create a single, comprehensive file with all the station data we need.

See also: Canadian/Mexican AM Station Search

Another country of interest but outside the North American realm is Australia. Under a separate post, Australian Mediumwave Database, I show where to find detailed technical information on Australian mediumwave stations.

The current build of Radio Data MW.

Mediumwave Oddities - Transmitter Power

2010-08-13T14:50:00.009-04:00

We've talked about geographical mediumwave oddities for the United States, let's shift the discussion to transmitter power. Again, we will use data from current FCC records, this time from August 7, 2010. There are 4784 licensed stations in this survey. I have found 4787 licensed stations in the database, one more than the 4786 total the FCC publishes. I am excluding WR2XJR-670, Portsmouth, Virginia, a questionable FCC record for a synchronous station, and WWWS-1400 and WWGP-1050, both of which are reported licensed and on the air, but have no current antenna engineering record in the FCC database.

Daytime and nighttime data differ, so I will try to be explicit on the figures presented.

THE BIG BOYS

As you probably already know, 50,000 watts (50KW) is the maximum power allowed for a US mediumwave station. All 50KW stations used to be Class A clear channel stations, but that is no longer the case. 50KW stations can be Class A, Class B, or Class D, depending on the area they serve.

THE DAYTIME

First of all, how many total stations are on the air during daytime hours?

All 4784 FCC-licensed stations can operate during daytime hours.

How many 50KW stations are there?

Throughout the FCC dragnet, there are 245 stations transmitting at 50,000 watts during daytime hours. 324 stations are transmitting at 20,000 watts or higher. 600 stations at 10,000 watts or higher. The vast majority, 4184 stations, transmit at a power under 10,000 watts.

Here's some figures for other power levels:

10,000 watters - 331
5,000 watters - 1172
1,000 watters - 1819
500 watters - 271

717 stations transmit with a power less than 1,000 watts during daytime hours.

Which station transmits with the lowest daytime power?

Lowly WBCP-1580, Urbana, Illinois with 135 watts. Only 10 stations total transmit with less than 200 watts.

What is the total power output of all stations combined?

A whopping 27,323,022 daytime watts! (27,323.022 kilowatts)

Currently, power companies in the US charge anywhere from about 8 cents per kilowatt hour to about 20 (Hawaii has the highest rate at 27 cents).

Considering 15 cents per kilowatt hour an average rate, how much does it cost to run all of these transmitters for one hour?

27,323.022 kilowatts per hour costs $4,098 each hour to operate. Over a 12 hour daytime period, the grand total paid to the power companies is an astounding $49,181, essentially 50 thousand dollars per half day in power costs alone.

THE NIGHTTIME

How many total stations are on the air during nighttime hours?

4178 stations can operate during nighttime hours, out of 4784 stations total. This leaves 606 stations which are licensed for daytime only operations.

How many 50,000 watt stations are authorized to transmit at this power level at night?

97 stations are at the 50KW level during nighttime hours, versus 245 during the daytime. 122 stations are transmitting at 20,000 watts or higher (versus 324). 212 stations at 10,000 watts or higher (versus 600). 3966 stations transmit at a power under 10,000 watts.

Here are the other figures for nighttime hours:

10,000 watters - 78 (versus 331)
5,000 watters - 408 (versus 1172)
1,000 watters - 1360 (versus 1819)
500 watters - 250 (versus 271)

2031 stations transmit with a power less than 1,000 watts during nighttime hours.

Under 1,000 watts, things start to get really interesting, as nighttime operations are a totally different ballgame than daytime due to greatly enhanced signal propagation. Many, many low powered stations abound.

Which station transmits with the lowest nighttime power?

We have a tie. 14 stations transmit with a flea-power signal of only one watt! In fact, 120 stations are on the air transmitting with less than 10 watts! Between 1 and 99 watts, there is at least one station transmitting at each unit of power level, i.e., at 1,2,3,4,5,6,7,8,9,10,11,12,13....47,48,49....all the way to 99 watts.

There are 1028 stations transmitting less than 100 watts at night. Of those, 908 are at power levels between 10 and 99 watts. Between 100 and 500 watts, we have 551 stations.

So, the record holders at 1 watt output level are these 14 stations:

WNBL-1540, Booneville, IN
WRFM-990, Muncie, IN
WGAB-1180, Newburgh, IN
KBOA-1540, Kennett, MO
WZRK-1550, Lake Geneva, WI
WJJT-1540, Jellico, TN
KLKC-1540, Parsons, KS
WSRY-1550, Elkton, MD
WSQR-1180, Sycamore, IL
KDYN-1540,Ozark, AR
KLEY-1130,Wellington, KS
WCKB-780, Dunn, NC
WPGR-1510, Monroeville, PA
WHFB-1060, Benton Harbor, MI

Of these, Indiana is the clear winner with 3 of the lowest powered stations in the US.

What is the total power output of all nighttime stations combined?

10,856,121 nighttime watts (10,856.121 kilowatts). This is opposed to the daytime total wattage output of 27,323,022 watts. The nighttime power level is about 40% of the daytime level. One hour of nighttime electricity costs the radio stations $1,628. Twelve hours of operation at night costs $19,541.

So, the total cost of mediumwave broadcast transmitter power in the US, operating 24 hours per day, comes to approximately $68,722, based on a 15 cents per kilowatt hour charge by the power companies!

How many of you mediumwave DXers have heard these flea power stations, under 10 watts? Maybe we should have a certificate award for receiving a prescribed number of flea powered stations, perhaps under 100 watts, or even under 10 watts?

Coming up next: Mediumwave Oddities - Towers

More power to you, mediumwave DXer!

Mediumwave Oddities - Geography

2010-07-31T08:05:00.007-04:00

Think you know mediumwave? Are you good at geography? Do you like statistics?

Let's look at the geographical oddities of the mediumwave band for the United States. Information has been gleaned from current FCC records, and includes only US-licensed stations. 4784 licensed stations were used to compile these statistics from the FCC database dated July 14, 2010.

EAST

Did you know that 21% of all US-licensed AM stations are east of Florida? This one surprised me.

Which US station is the farthest east? Remember, east goes all the way to the International Date Line.

If you guessed a station in Maine, you would be wrong by a great margin. The farthest US station in the eastern hemisphere is KCNM-1080 (5KW), Saipan, Northern Marianas at 145.714E longitude. Next would be KGUM-567 (10KW), in Agana, Guam at 144.759E longitude. Three other stations in Guam are #3, #4, and #5 farthest east in longitude, west of the International Date Line.

So, how about the continental US? Are we there yet?

Think Carribbean. WSTX-970 (5KW), in Christiansted, US Virgin Islands is next farthest east at 64.693W longitude, and the most eastern US station in the western hemisphere. Five other US Virgin Islands stations are next.

Next comes a slew of stations in Puerto Rico, in fact 75 of them. The farthest east in Puerto Rico is WMDD-1480 (5KW), at 65.64W longitude.

Now we finally come to the continental US. The most easterly station in the continental US is WXME-780 (5KW), Monticello, Maine at 67.817W longitude. However, there is an application on file for a "NEW" AM station in Calais, Maine at 67.266W longitude which will take the title if it ever goes on the air.

But what about Florida, you ask?

Florida is not even close in the running. WWRF-1380 (1KW), Lake Worth, Florida at 80.072W longitude is the station farthest east in Florida. Astonishingly, there are 921 stations up and down the east coast of the continental US which are farther east than Florida's WWRF-1380, and 1007 stations farther east in total, clear to the International Date Line, all licensed to the US via the FCC.

Amazingly, 1007 stations (21%) of 4784 licensed FCC stations are east of Florida.

Which is the most easterly NPR (National Public Radio) station?

WFPB-1170 (1KW) Orleans, Massachusetts at 70.01W longitude.

Most of us know that "K" stations are west of the Mississippi, and "W" stations are east of the Mississippi, except for a few exceptions, like KDKA-1020 in Pittsburgh, PA and KYW-1060 in Philadelphia, PA and WOAI-1200 in San Antonio, Texas.

Which is the farthest east "K" station, east of the Mississippi River?

That would be KCNM-1080 (5KW), Saipan, Northern Marianas at 145.714E longitude. It is 7788 miles east of Wasington, DC where the FCC is located, and most definitely east of the Mississippi River. The most easterly "K" station in the lower 48 states is KYW-1060 (50KW), Philadelphia, Pennsylvania at 75.248W longitude.

WEST

Which US station is the farthest west?

We have two winners. KJAL-585 (5KW) Tafuna, American Samoa at 170.776W longitude and WVUV-648 (10KW), Leone, American Samoa at 170.776W longitude, both in the South Pacific and licensed by the FCC, some 7035 miles west of Washington, DC. They transmit from the same location.

Which is the most westerly station in the lower 48 states?

KBIS-1490 (1KW), Forks, Washington at 124.388W longitude. There are 72 stations farther west of this, all in Alaska or the Pacific Ocean.

Which has more AM stations, Hawaii or Alaska?

Hawaii has 30; Alaska has 40. Alaska is the winner.

Which is the most westerly Alaskan station?

KICY-850 (50KW), Nome, Alaska at 165.314W longitude. There are a total of 6 Alaskan stations that are farther west than the most westerly Hawaiian station, KUAI-720 (5KW), on the island of Kuai.

Which is the most westerly NPR station?

KOTZ-720 (10KW), Kotzebue, Alaska at 162.568W longitude.

Which is the farthest west "W" station, west of the Mississippi River?

The prize goes to WVUV-648 (10KW), Leone, American Samoa at 170.776W longitude. So much for WOAI-1200 in San Antonio, Texas! WOAI-1200 is the most westerly in the lower 48 states.

NORTH

Which US station is the farthest north?

KBRW-680 (10KW), Barrow, Alaska at 71.256N latitude.

Which NPR station is the farthest north?

Again, KBRW-680 (10KW), Barrow, Alaska at 71.256N latitude.

How about the continental US? Which station is the farthest north?

We have a tie. KVRI-1600 (50KW), Blaine, Washington at 48.954N latitude and KARI-550 (5KW), Blaine, Washington at 48.954N latitude.

How come a station in Maine isn't the farthest north?

The most northern station in Maine is WFST-600 (5KW), Caribou, Maine at 46.886N latitude. 180 stations are farther north than WFST-600, and all are scattered from Minnesota all the way to Alaska.

The geographical center of the lower 48 states lies outside of Lebanon, Kansas, in the middle of what used to be a hog farm.

Are there more stations to the north or to the south of this location?

There are 1814 stations to the north and 2970 stations to the south of Lebanon, Kansas.

SOUTH

Which US station is the farthest south? Think outside of the continental US.

Another tie. KJAL-585 (5KW) Tafuna, American Samoa at 14.357S latitude and WVUV-648 (10KW), Leone, American Samoa at 14.357S latitude. Coincidentally, these two stations are not only the farthest south, but also the farthest west.

Which is the most southerly station in the continental US?

WKIZ-1500 (250W), Key West, Florida at 24.567N latitude. The Florida Keys have 3 stations - 2 in Key West, and 1 in Marathon Key.

How about Texas? It's pretty far south.

The most southerly station in Texas is KVNS-1700 (8.8KW), Brownsville, Texas at 25.949N latitude.

And California?

That would be KURS-1040 (360W), San Diego, California at 32.694N latitude. Texas is much farther south than California.

How many stations are south of the continental US?

There are 118 stations south of the continental US, that is, south of Key West, Florida. All are in the Pacific or Caribbean.

The Mississippi River runs north and south through the country, dividing the US east to west approximately at St. Louis, Missouri (90.18W longitude).

Are there more stations to the east or to the west of St. Louis?

There are 1990 stations west of St. Louis and 2794 stations east of St. Louis. The majority of stations are to the east of St. Louis, in fact, 71% of them.

IBOC

How about some IBOC stats?

There are 293 licensed IBOC stations. Two are silent at the moment.

The most westerly IBOC station is KOTZ-720 (10KW), Kotzebue, Alaska at 162.568W longitude. It is also the most northerly IBOC station and the most westerly NPR station.

The most easterly IBOC station is WIPR-940 (10KW), San Juan, Puerto Rico at 66.141W longitude. It is also the most southerly IBOC station.

There are 128 IBOC stations west of the Mississippi River. There are 165 IBOC stations east of the Mississippi River.

Which state has the most IBOC stations?

California wins with 32. Runner up is Florida with 25, followed by Colorado at 17. New York has 16, and both Texas and Ohio have 15 each.

Which state has the fewest IBOC stations?

Several are tied. Kentucky, Mississippi, North Dakota, Nebraska, and South Carolina have 1 each. Arkansas, Delaware, Idaho, Louisiana, Maine, Montana, New Mexico, and Nevada have 2 each.

Which state has the most IBOC NPR stations?

Surprise! Alaska wins with 6. Alaska also has the most NPR stations overall at 9.

ERRATA

How many "K" call signs?

1907.

How many "W" call signs?

2877. The "W"s win by a huge margin.

We have a KAAA and a KZZZ, but no WAAA or WZZZ.

What are the oddest call signs?

Puerto Rico gets the win here. WA2XPA-680, WI2XAC-740, WI2XSO-1260, and WI3XSP-1260. These four are experimental synchronous stations. Usually AM synchronous station call signs are named the same as the host station, like KKOB-770 in Albuquerque, New Mexico, which runs one in Santa Fe, also KKOB.

Which state has the most stations?

Texas takes the prize with 298, then California with 250.

Surely New York is next, right?

No. New York is #8 ranked with 168. Florida (227), North Carolina (219), Tennessee (185), Georgia (183), and Pennsylvania (180) all have more stations than New York (168). Weirdly, New York ranks just above Alabama, which has 152.

Which state has the fewest stations?

That would be Delaware with 10, followed by Rhode Island with 15 and Vermont with 19.

Coming up next: Mediumwave Oddities - Transmitter Power

Note:

Station powers listed are for their daytime service. Nighttime powers may be lower in some cases.

Digital Radio Update

2010-07-25T08:28:00.024-04:00

Let's take a look at the current state of the digital radio conversion process in a few selected countries around the world.

THE UNITED STATES

Almost a year has passed since I reported on The IBOC MESS In North America. Since then, hybrid-digital IBOC conversions (HD Radio) on the US mediumwave AM broadcast band have come to a near dead stop. There seems to be little excitement for new stations to jump on the Ibiquity AM bandwagon, what with a scattered amount of dedicated equipment available and marginal listener interest, not withstanding the large cash outlay stations need to get signed up and converted. Available receiving equipment seems to be a few clock radios, some home sound system type tuners, and car radios (which seem to be coming on strong). Portables have largely been ignored. Sangean had plans to make an intriguing little AM/FM model, the DT-600HD, however the AM band on this unit was to be traditionally analog. They dropped the product before it got to the marketplace.

Last year at August 27, 2009, we had 289 licensed IBOC AM outlets, per FCC files. As of this writing we have 293, and two of them are silent. This is a net gain of only four new registrations in the last 11 months. In the past year there have been reports of several stations switching off their digital signal due either to problems, interference complaints, or lack of interest, so the actual count of stations currently transmitting IBOC is almost certainly under 290. Using the figure 293 against the total number of licensed AM broadcast stations in the US (4786), the AM IBOC factor is 6.1%. At this rate, AM IBOC cannot sustain itself.

Then, there is the adjacent channel interference problem, particularly bad at night, which many still complain about. And rightfully so. Nightly, digital broadband hash continues here in the northeast and other parts of the country on the mediumwave band. Earlier this year, one evening after dark I was driving through Phoenix, Arizona trying to listen to local AM station KMVP (itself an IBOC station) on 860 KHz. It transmits at 1KW. Every time adjacent channel KOA-850 (another IBOC, at 50KW) out of Denver, Colorado peaked, KMVP was not receivable due to the digital hash. It was maddening.

Earlier this year, Ibiquity announced 2010 fire sale pricing (good through December 31) for new stations wishing to join the digital "revolution", with the stipulation that they be "stations eligible for discount pricing", whatever that means. The existing $25,000 main channel licensing fee was reduced to a remarkable figure of $10,500 if payment is made up front. Monthly payment plans (at an overall higher total figure) for those stations less able to scare up this kind of money all at once were also instituted. It seems that the original higher flow of incoming cash might be slowing down. Ibiquity claims that one new digital station goes on the air on the average of every four days. I guess this must mean FM, as the AM figures don't support this claim. It will be interesting to see if the fire sale continues into next year.

So what is the current market share for HD Radio in the US? A 7 month old Bridge Report hinted at it.

12/15/2009 Bridge Ratings: New Media's Effect On Radio Lessening

"HD Radio, though it reaches only about 650,000 people, is attracting 'considerable listening time' of about 11.5 hours a week", though Bridge says "that's down from previous surveys, attributing the change to a larger number of HD receiver owners, diluting the impact of the heavy users."

"Respondents were also asked what audio devices they use every day, with a choice of AM/FM radio, HD Radio, cellphone, satellite radio, and Internet radio. Nearly 90 percent of radio listeners also use a cellphone every day, while more than 44 percent use an MP3 player. About 35 percent listen to Internet radio every day, with satellite radio and HD Radio well behind."

6/30/2010 Bridge Ratings: Is Terrestrial Radio Ready for a Digital Future?

Things are not moving along very quickly. Back to mediumwave, we can only hope that Ibiquity eventually gives up on the mediumwave band, or the government does, or both, and they take the AM patient off of life-support.

Beyond our borders, several other countries have issued mandates to go digital for some or all of their radio broadcasting services. Let's examine some of their stories.

MEXICO

4/14/2010 Mexico Is Set to Elect IBOC

Information out of Mexico is paltry, and I have seen nothing new since April. It would seem that this is a done deal, with Mexico on the verge of adopting IBOC as their standard. Back in May 2008, a 200 mile wide border zone was established along the US - Mexican border allowing Mexican AM and FM stations to use the IBOC format to "take decisive action so that the country’s AM and FM radio stations in the zone located within 320 km of the northern border of Mexico can transmit at the same technological level so that they can provide the benefits of quality service to the radio listening public."

Supposedly, there are two, or six, or nine IBOC outlets, depending on what you read, and at least two more deeper down in Mexico itself in or around Mexico City (XHDL and XEDA). The two call signs I have seen reported along the US border are AM outlet XEEZ 970 Radio Palacios from Caborca, Sonora, and the other, an FM outlet, XHTY-FM 94.5 in Tijuana. The station news is all old news anyway and reported a long time ago, way back in June 2008. I have heard no other IBOC-rollout fanfare since then.

Suddenly in early 2009 Mexico announced that it intended to convert all AM radio station outlets to FM, country-wide, a wholesale disbanding the AM service. They even published a schedule of the conversion dates, to take place between August of 2009 and August of 2010 (see page 8).

Whether this eventually happens or not is anyone's guess, but you can bet on it not happening by next month. Local reports out of Mexico indicate that some regional areas have abandoned the AM mode, particularly in the southeast. The government's general idea, I think, was to force the big city AM outlets to convert to FM (and in the future, IBOC), and let the rural outlets languish and eventually disappear. However there was no lack of border blasters in southwestern Arizona, where I spent last winter. The Nogales to Tijuana border strip has a sizable number of AM outlets, but none running IBOC as far as I can remember hearing. Assuming I get to Arizona again this winter, I will pay more careful attention to what is coming out of Mexico. Needless to say, the AM to FM conversion in Mexico is coming along slowly. And IBOC even slower. So where does this leave Mexican AM IBOC?

Curiously, Mexico's announcement of being on the brink of voting to adopt the IBOC methodology is some months old now, with no action since. It seems they can't pull the trigger. Maybe they realize that it's just a whole lot of money and effort for no good end, at least on the AM side. Or maybe they are dragging their feet waiting to see what happens with IBOC in this country. IBOC may be on life-support for the mediumwave band in the US, but FM has greater presence. As of this writing, 1569 stations (8 not on the air) are shown with IBOC permits in the FM service. This is compared to a total of 9608 full-fledged FM stations on the air, commercial and non-commercial, 130 of them showing silent at the moment. Using the figure 1569 against the total number of licensed FM broadcast stations (9608), the FM IBOC factor is 16.3%. Still not a great showing. However, listenership seems to be coming around.

May 2010 FM HD Radio is Becoming a Fact of Life for American Radio (be careful with this news, it is an Ibiquity article)

CANADA

Canada (having wanted to go with the DAB standard) seems to be stalled on the whole digital radio broadcasting question, according to a recent article this month in Radio Magazine Online. The article reports that "government observers agree that the service has reached the end of the line....with DAB's imminent demise, increased demand for analog FM frequencies is taking place in Canada's urban areas."

IBOC, where for art thou?

"While posts in online Canadian radio forums suggest a preference for HD Radio among hobbyists, government regulators and industry representatives still treat the the option with caution. Canada's Communications Research Centre, a governmental research body with an advisory role on telecom policy, has developed its own coverage analysis tool dubbed COVLAB to evaluate digital radio coverage and spectral compatibility, rather than simply deferring to U.S. data. IBOC digital radio testing has been conducted in Canada since 2006, and the Canadian government has said that it will accept experimental HD Radio digital hybrid applications from licensed FM stations, though few stations have stepped up to do so."

"So industry opinion on IBOC's potential in Canada is checkered at best. With many stations moving away from AM altogether, and interference concerns among those who remain, AM HD Radio is probably a nonstarter."

Exactly what I've been talking about. Canadian reader Greg writes:

"DAB failed in Canada because there was almost no public awareness of it and virtually no receivers on the market that could receive it. I never saw anyone selling or even advertising DAB receivers, and never even heard any mention of the service anywhere except on radio hobbyist sites and mailing lists. Canada's DAB system was a bit different than that adopted in the U.K., operating on a different frequency band. I wonder if it would have been more successful had we adopted the British standard, which would have enabled us to use receivers designed for the U.K.?"

7/7/2010 Canada DAB Shut Down

Outside of North America, at least four more countries are either entertaining or have adopted Digital Audio Broadcasting (DAB) or Digital Radio Mondiale (DRM) schemes. Europe and many parts of Asia have gone or are going with the DAB or DRM schemes.

Also see:

Digital Radio Mondiale Home Page
Country Information for DAB, DAB+ and DMB

BRITAIN

Britain is an interesting story, in and of itself. The government is going gangbusters for DAB "Digital Britain" via the Digital Economy Act, and pushing it as hard as they can. However, the public and the pundits are panning it for now as "not ready", if ever. The government stipulates that the 2015 switchover "will go ahead only if 50 per cent of radio listening is via 'digital platforms' by 2013." Many say that will never happen by that soon a date, and that the switchover should be delayed for a period of ten years or more. At the forefront is the BBC. The BBC's digital radio stations now cover 86 per cent of the country (signal pattern coverage). The corporation has built 50 transmitters in the last year and plans 60 more in the next year to increase coverage to 90 per cent. Of course, nationwide, the thrust is mostly FM.

Whether their switchover happens by 2015 is the guess of the decade. Figures published showed that the audience share for digital radio in Britain – including listeners on digital TV and the internet – is rising at a record rate, up to 24 per cent from 20.9 per cent in the previous quarter (first quarter, 2010).

We shall see, if we all live long enough. No IBOC for Britain.

There is lots of interesting digital conversion news out of Britain:

7/22/2010 More On The Digital Economy Act

7/8/2010 Digital Radio Speech by the Culture Minister, Ed Vaizey

7/8/2010 Relax. Digital radio switchover will now never happen

5/23/2010 Digital radio switchover gets poor reception

4/8/2010 Say goodbye to your transistor radio, digital switchover is coming

9/9/2009 Britain Mulls Over Digital Radio Transition

6/16/2009 Digital Britain: Analogue radio switch-off set for 2015

INDIA

India is going with DRM, and All India Radio has just ordered a fair amount of equipment. All India Radio is also big into shortwave, much of it used for national regional service. On mediumwave, transmitters there tend to be big boys - 100KW, 200KW, and 300KW to extend the coverage area. On the books are 34 new MW transmitters, upgrades to 36 existing MW transmitters and the purchase of 5 SW transmitters and other associated equipment. Interesting, I see no mention of FM in here.

7/1/2010 All India Radio tender notice for DRM digital transmitters

4/10/2010 Indian government approves country’s digitalisation plan using DRM

AUSTRALIA

Australia has gone with the DAB+ method, a variation of DAB. All commercial and public service broadcasters are now broadcasting digital radio in Sydney, Melbourne, Brisbane, Perth and Adelaide. Australian commercial digital radio services switched-on progressively in May and June 2009 in the five state capital metropolitian areas. The public service broadcasters switched on 1 July 2009. A recent report revealed, "....the industry recently released figures indicating there were already nearly 500,000 people listening to digital radio across those markets."

"There are no plans at this stage to switch off AM and FM radio services", the report said. It continued on, "As there is an estimated five radio devices per home, listeners must be given time to change over all of their radios before any discussion of the switch off of analogue services. In addition, planning needs to continue for the switch on of digital services to the rest of Australia outside of the five metropolitan capital cities."

"It is expected that it will be some years before digital radio is extended to the bulk of the Australian continent. Australia's vast distances and low population density are not well suited to the propagation characteristics of DAB+ and it is therefore likely that a standard other than DAB+ will be adopted for serving areas outside the major cities."

At the moment, it looks like IBOC has lost out here. Australia may use DRM to fill in the nether regions if DAB+ doesn't work out.

Digital Radio In Australia (Wiki)

Digital Radio FAQs For Australia

7/19/2010 ABC Radio Is Now Digital (including AM outlets)

5/5/2010 Digital radio trial to begin in Canberra

8/13/2009 Rollout Of Digital Radio In Australia (announced in 2007)

BRAZIL

Brazil is huge. Ibiquity has done IBOC testing here, and the HD Radio system has been used on a trial basis by a number of commercial broadcasters since 2005. Brazil is the second-largest radio country in the world in terms of station count, behind the United States. Brazil has more than 3,000 commercial stations and about an equal number of low-power community radio stations. This would be huge profit for Ibiquity.

"Brazil's target date for full roll-out of an IBOC approach to digital radio is the year 2016. The Congress of the Brazilian Association of Radio and Television Broadcasters is expected to make a standards announcement by the end of this year or in early 2011. However, there is also interest in Digital Radio Mondiale's DRM30 and DRM+ technologies. The possibility exists that the country will adopt different standards for AM, FM and shortwave."

"While AM and tropical-band shortwave remain important in large swaths of Brazil, DRM may be better positioned than Ibiquity's HD Radio AM for these wavebands, according to anecdotal comments on Brazilian digital radio message boards, blogs and press accounts. Yet HD Radio has more receivers on the market than does DRM. If regulators opt for DRM on AM and for HD Radio on FM, there is a concern that the rollout could be delayed by the manufacturing time necessary to produce dual-standard receivers, according to these accounts. Ibiquity publicly has supported the use of DRM30 for shortwave services in Brazil. It also supports the concept of multi-system tuners capable of receiving both HD Radio on AM/FM and DRM on shortwave."

IBOC is at the doorstep here, but not through the door yet. Again, like Australia, the rural regions may need to adopt the DRM technique for the AM service. We will soon see what Brazil decides.

5/27/2010 Brazilian Broadcasters make public open letter in support of DRM

5/12/2010 Brazil Could Pick Digital Standard in 2010

IBOC INTERNATIONAL

According to the Ibiquity web site, there are a handful of other countries testing and evaluating IBOC digital radio as of this writing. They are: Argentina, Austria, Canada, Chile, France, Hong Kong, Indonesia, New Zealand, Nigeria, Phillippines, Poland, Switzerland, Thailand, and Ukraine.

Ibiquity International

The AM Broadcast Station Self-Inspection Checklist

2010-07-19T13:53:00.013-04:00

AM Broadcast Station Self-Inspection Checklist (Sept. 2009)

As a mediumwave DXer and a person interested in radio in general, you might be interested in what the FCC requires of mediumwave AM broadcast stations in their day-to-day operation. A document exists, called the AM Broadcast Station Self-Inspection Checklist. The FCC has developed it to assist broadcast station management in conducting a self inspection of their station. It provides an opportunity for the broadcaster to review and correct any deficiencies associated with the operation of a station without an actual on-scene visit (and citation!) by the Commission. Some interesting entries are to be found, and I will cover them in this article.

STATION LOGS AND RECORDS

First of all, the paperwork. Stations must keep logs and records. What is the difference, you might ask? What goes into a log and what goes into a record?

Section 1B. STATION LOGS/RECORDS:

STATION LOGS include entries pertaining to equipment status, equipment calibration, the Emergency Alert System (EAS) and, when applicable, the recording of tower light outages.

STATION RECORDS include, but are not limited to chief operator designations, equipment performance measurements and AM Directional field strength measurements.

Station logs and records are to be retained for a period of two years.

STATION IDENTIFICATION

This is a hot topic with me. Stations seem to identify less and less. There are stations (ESPN Radio, Radio Disney, are you listening?), which never seem to identify with call signs, making our task as mediumwave DXers a little more difficult. What is the rule? Well, here it is spelled out in exact terms:

Section 1D. STATION IDENTIFICATION:

Station identification shall be made at the beginning and ending of each period of operation, and hourly, as close to the hour as feasible, at a natural break in program offerings. The identification shall consist of the station's call letters immediately followed by the community of license. Any reference to additional communities must be made after the community of license. The name of the licensee, or the station frequency, channel number, or both, may be inserted between the call letters and community of license. No other insertion is permissible. Simulcasted AM and FM stations may identify jointly if owned by the same licensee.

Not much room for ad-lib here. Stations must identify at least once per hour on the hour, and in a strictly defined format. Exclaiming, "ESPN Radio!", "Radio Disney 1650!", "Power 101!", or "K-Lite 107!" cannot be used for the official identification. They must state the station's call letters and community of license at minimum. Optionally, they may insert the owner's name, or frequency, or channel, or all of these. Finally (capitalization mine): "NO OTHER INSERTED INFORMATION IS PERMISSIBLE." What's so hard about this?

ALL ABOUT BROADCAST TOWERS

A tower is a thing of beauty to the radio aficionado. Somebody even produces a tower calendar. Ah, the mediumwave broadcast tower! Think of it! Stately, striped sentinels with strobe lights flashing, they number thousands and thousands across the country, each emitting invisible waves of electrons through the late night air, spanning that mysterious thing called "the ether" to deliver communication to unknown distant masses. It conjures up thoughts of far-away points on the landscape, souls crouched in cramped corners with headsets fixed in the dark of night, straining to make sense of distant babble through static crashes and heterodynes. That would be me. The whistle of a far off freight train gives the same feeling of wonder. So, back to the broadcast tower - what is the broadcast station's responsibility?

Well, any tower over 200 feet tall or even if under 200 feet and an impediment to aircraft navigation must be registered (FCC Form 854). It also must be lighted and painted. We've all seen the lighted towers of AM broadcast stations. Ever wonder about those lights? What happens when one goes out? Who checks to see if they are burning, and how often?

Section 2C. TOWER LIGHT OBSERVATIONS:

The lighting on tower structures is to be observed at least once every 24 hours either visually or by observing an automatic indicating device; or alternatively the licensee/tower owner may provide and maintain an automatic alarm system to constantly monitor the lighting on a structure. All automatic or mechanical control devices, indicators, and alarm systems are required to be inspected at intervals NOT TO EXCEED 3 months.

Relief here, maybe, for the engineer. As of 1996, responsibility for tower lighting (and painting) lies with the owner of the structure, not necessarily the station licensee. However, at least a human doesn't have to go outside once a day and look to see if the lights are burning. An electronic monitoring device can perform the task. However, then the MONITORING DEVICE must be inspected at least every three months! Note: A recent directive relaxes this requirement to a year.

More on tower painting:

Section 2D. PAINTING/LIGHTING:

The station authorization and/or tower registration specifies the painting and lighting requirements for your operation....The licensee must make certain that the number and placement of paint bands and lighting match exactly with that shown on the station authorization and/or tower registration. The licensee/tower owner should also be aware of the requirement to clean or repaint tower structures as often as necessary to maintain good visibility to aircraft.

Exacting detail is found in FCC Form 715-715A:

Antenna structures shall be painted throughout their height with alternate bands of aviation surface orange and white, terminating with aviation surface orange bands at both top and bottom. The width of the bands shall be equal and approximately one-seventh the height of the structure, provided however, that the bands shall not be more than 30.48 meters (100 feet) nor less than .46 meters (1 1/2 feet) in width. All towers shall be cleaned or repainted as often as necessary to maintain good visibility.

All high and medium intensity lights shall be synchronized to flash simultanously at 40 pulses per minute. The light system shall be equipped with a light sensitive control device which shall face the north sky....

Additionally, Form 715-715A goes into great detail on the positioning and intensity of tower lights.

Section 2D, PAINTING/LIGHTING finishes by saying:

....One of the most common problems associated with tower painting is the feedlines that are on the outside legs of a tower. In many cases, the tower is painted correctly, but the solid black colored feedlines defeat the purpose of the painting by covering the outside legs of the tower. The licensee/tower owner should make certain that the feedlines are also painted in such instances. This does not apply in cases where the tower is authorized for strobe lighting.

To wit: If you run your feedlines up the outside of the tower leg, paint the feedlines to match the tower striping! So that's what they call that red color on towers: aviation surface orange.

And let's not forget to notify the Federal Aviation Administration when the lights go out:

Section 2E. FAA NOTIFICATIONS:

The tower owner/licensee is to notify the Federal Aviation Administration (FAA) at (Phone: 877-487-6867) within 30 minutes of the observation of an improper functioning or extinguished top steady burning light or ANY flashing obstruction light regardless of its position on the structure. Such improper functioning beacons include non-lighted beacons as well as those that are lighted, but non-flashing. Notification is to also be made immediately to the FAA once the beacon or steady burning top light is returned to service. Notification is not required when side light outages are observed....

Bottom line: you have 30 minutes to notify the FAA if your top tower light or one of your flashing lights goes out!

TRANSMITTER POWER

Lots of rules exist about checking and maintaining station transmitter power and purity of signal. Stations are granted the privilege to transmit at a certain output power. How much leeway do they get to be over or under powered?

Section 4A. POWER:

All AM stations are to maintain antenna input power between 90% and 105% of that authorized.

Interesting, we are allowed no more than 5% over and 10% under. Accordingly, a 50KW station can actually run between 45KW and 52.5KW and still be in compliance. I wonder how many 50KW stations push the envelope and run that extra 2.5KW? Or more?

Section 4A continues on, concerning failure to maintain a minimum power level (90%):

....The power is to be maintained as near as practicable to the station's authorized power. In the event that it becomes technically impossible to operate at authorized power, a station may operate at reduced power for a period of not more than 30 days without specific authority from the FCC. If operation at reduced power will exceed 10 consecutive days, a notification must be sent to the FCC, Media Bureau, Washington, D.C. 20554, no later than the 10th day. If normal power is restored prior to the expiration of the 30 day period, the licensee must notify the FCC upon restoration of normal operation.

It's kind of like highway speed limits. The cops will ticket you for going more than 10 mph over and let you by at 5 mph over. You will also get ticketed for going to slow on certain roadways, i.e. 35 mph in a 55 mph zone.

So how exactly does a station measure its power level accurately to assure compliance with the FCC?

MEASURING POWER

Okay, we need to check the power. Do we just read it off a meter on the console and log it? Well, perhaps.

Section 4B. DIRECT vs INDIRECT METHOD (of monitoring power output):

The antenna input power of AM stations must be determined using the direct method. However, the indirect method may be used on a temporary basis when it is not possible or appropriate to use the direct method due to technical reasons.

Direct Method. Two possibilities are allowed here:

1) Employ a suitable instrument for determining the antenna's input power directly from the RF voltage, RF current, and phase.

2) Calculate the product of the licensed antenna or common point resistance at the operating frequency and the square of the indicated unmodulated antenna current at that frequency, as measured at the point where the resistance has been determined.

Indirect Method.

Apply the appropriate factor (they mean efficiency factor here) to the input power to the last radio frequency power amplifier stage of the transmitter, using the following formula:

Transmitter output power = Ep x Ip x F

Where:

Ep = DC input voltage of final radio stage.
Ip = Total DC input current of final radio stage.
F = Efficiency factor of the transmitter.

The value of the efficiency factor, F, is to be determined and a record of its value is to be maintained and available upon request. Licensees must make certain that all duty operators know which method of power determination is being used and how to calculate the output power based on that method.

Furthermore, how does a station ensure that its signal is clean and meets prescribed standards?

MORE PAPERWORK

Not only must a station monitor power and other parameters, but it must have procedures in place on how and when to do it.

Section 4G. MONITORING PROCEDURES:

The licensee must establish monitoring procedures and schedules for the station. Monitoring procedures and schedules must enable the licensee to determine compliance with operating power, modulation levels, AM modes of operation, and where applicable with antenna tower lighting and AM directional antenna parameters. Licensees should be able to provide upon request made by the FCC, the monitoring procedures and schedules they have established for each station. In the event that an AM broadcast station is operating with a mode of operation not specified by the station license, then the station operation must be terminated within 3 minutes or the station output power must be reduced sufficiently to eliminate any excess radiation. This includes AM Directional stations with parameters or monitoring points out of tolerance with the station authorization.

Additionally, the directive states:

....In the event that an AM broadcast station is operating with power in excess of 105% of authorized, or with excessive modulation, then station operation is to be terminated within 3 hours, unless corrective action is taken prior to that time.

All right, it basically boils down to this: A station must have a monitoring procedure in place (obviously written), and a schedule in place for when to do it. They must monitor, at minimum, the power output, modulation level, AM quality, antenna lighting, and antenna directionality. And if their monitoring shows that they are out of compliance, they must shut down within three minutes, or at least reduce power to bring them back into compliance! The only exception is if power is exceeded or modulation is excessive - in which case they have three hours to terminate operation.

FREQUENCY

A station is licensed to transmit on a specified frequency. Along with measuring power output, a station must also ensure that it is on frequency. How accurate is it required to be?

Section 4C. FREQUENCY:

The carrier frequency for monophonic transmissions or the center frequency for stereophonic transmissions may not depart more than 20 Hz from the assigned frequency.

Tune across the broadcast band some night when conditions are good and listen for heterodynes. On any given channel there should be none, ideally. You have to listen carefully. Listen for that faint, low "whump, whump, whump" beat note caused by one station being ever so slightly off frequency, usually only a matter of cycles. 20 Hz offset is too low to hear as a tone. It is more of a rapid, dull thump-thump-thump, 20 times per second. If you hear a tone, a station is way off frequency, much more than 20 Hz (cycles). Surprisingly, you will find some.

MODULATION

Over-modulation is sometimes a no-no, too much over-modulation is a definite no-no. It results in distortion of recovered audio when the signal is demodulated, and worse, interference to stations on nearby frequencies due to the spurious byproducts. Here's what the FCC has to say about it:

Section 4D. MODULATION:
In no case shall the amplitude modulation of the carrier wave exceed 100% on negative peaks of frequent recurrence, or 125% on positive peaks at any time.

Slight over-modulation on the positive portion of the waveform is sometimes used for a more punchy sound, and works within limitation.

Any time you exceed 100% modulation on the negative portion of the waveform, it is clipped because you can't have less than zero carrier signal; that clipping generates high order harmonics that cause sidebands far outside of your intended channel and will interfere with other stations above or below the operating frequency.

POWER CHANGES FOR DIFFERENT TIMES OF DAY

Back to station output power again. If a station's service is not "Unlimited", it will generally be required to operate at different power levels for daytime, nighttime, and possibly even during the "Critical Hours" period. Critical Hours are the first two hours of daylight after sunrise and the last two hours of daylight before sunset.

Of course throughout the year, sunrise and sunset times are changing every day, therefore, stations must be constantly updating the times when they change power levels. The FCC is very specific on this. Let's see what this section of the document has to say:

Section 4I. POWER CHANGES:

Most AM stations utilize more than one power mode of operation. In addition to the normal authorized daytime power many stations operate under the reduced power pre-sunrise service authorization (PSRA) and post-sunset service authorization (PSSA)....Some stations will have reduced power nighttime operating authority and a few stations have a specified critical hours reduced power authorization. The times when power changes are to occur are clearly shown on the station authorization and in readily available sunrise/sunset tables.

(See http://www.fcc.gov/mb/audio/bickel/srsstime.html for a table of the sunrise/sunset times for your area).

Any unauthorized departure from an operating schedule will be considered as a violation of a material term of the license. It is the responsibility of the licensee to maintain calibrated time keeping devices, power switching devices and other equipment necessary for the timely change in power to occur as authorized. In addition, should the station be operated with more power than authorized for that time of day, then all operation is to be terminated within 3 minutes. The logging of power mode changes is not required unless the station is operating out-of-tolerance with any operating parameter. However, licensees are encouraged to do so.

As already stated, the FCC is very specific on power changing. Stations must keep accurate timing and change their power accordingly and on time. They must determine (on their own), their local sunrise/sunset time and change power precisely at that time. If they are out of tolerance by as little as three minutes, THEY MUST SHUT DOWN OPERATION. This is a stringent requirement. Violation of this requirement is a violation of the terms of their license. I would venture a guess that there are more than a few stations that are not changing power exactly on time. I know of some locals that are most definitely not within the three minute window.

So there you have it - the FCC's basic checklist on how to run an AM broadcast radio station. Hope you enjoyed it.

LINKS

Other FCC self-inspection checklists

Review Of The Tecsun PL-380 DSP Receiver

2010-06-19T12:41:00.034-04:00

With emphasis on mediumwave reception
And comparisons to various radios
-by Radio-Timetraveller

Purchased From: Anon-co (eBay)
Price: $45.99 + $24.00 shipping ($69.99 total)

Serial #: 369-2010-0202-752 03/2010

INTRODUCTION

The Tecsun PL-380 DSP Digital Receiver is one of the newest offerings in the ultralight-sized category of pocket receivers. It uses the industry's first fully integrated, 100% CMOS AM/FM/SW/LW radio receiver chip, the Silicon Labs Si4734. It tunes the longwave, mediumwave, shortwave and FM bands, and uses the latest in software-based digital signal processing to provide an outstanding choice of filter selectivities of 6 KHz, 4 KHz, 3 KHz, 2 KHz, and 1 KHz, minimizing interference. This little receiver is truly a quantum leap in technology.

Longwave coverage: 153 - 513 KHz
Mediumwave coverage: 520 - 1710 KHz (9 or 10 KHz split)
Shortwave coverage: 2300 - 21950 KHz
FM coverage: 64 - 108 MHz

This review is lengthy and quite technical in places. It is purposely slanted toward the mediumwave DX enthusiast, mainly because I am one and that's why I bought this radio: to further pursue this hobby of mediumwave DX. Virtually all of what is said in terms of functionality and technical specification can also be applied to the shortwave and FM sections of this radio.

SHIPPING AND ARRIVAL

This is my first radio purchased directly out of China (Hong Kong), so I was a little nervous. Seller Anon-co sells these and other radios via eBay. It has been a good experience and exceeded my expectations. Purchase is easy through Pay-Pal. Joyce, the sales agent for Anon-co, contacted me via e-mail within 24 hours of my web purchase introducing herself and asking my preference of color for the radio. Three styles are available: silver, grey, and black. I chose the black one.

The radio was shipped out of Hong Kong within 48 hours via air post. A tracking number was provided for the parcel, shipped by a Hong Kong shipping company. The radio arrived 13 days later in New York via US Postal Service registered mail.

The PL-380 is physically small, fits in a shirt pocket, and is just a little larger (by 5/8 inch width and height) than my Kaito WRX911. It was packed in a Tecsun box, the box itself in a heavy duty bubble-wrap envelope. Radio size is 5-1/4 inch wide x 3-3/8 inch high x 1 inch deep. It arrived in good shape, complete with Hong Kong stamps on the envelope for the stamp collector.

ACCESSORIES

The PL-380 comes with a nicely equipped accessory package. Accessories include a nice zippered cloth case with inside pocket and small foldover pouch for earbuds, an external antenna wire with mini connector and curtain clip, earbuds, 3 NiMH batteries (1000 mAH), a USB charging cord, and a manual.

MANUAL

The manual, in English, contains 29 pages. It is well-written with an acceptable amount of Chinese-English speak. Included in the radio description are many graphics showing how to use the various functions. The inside front-cover has a nicely detailed block diagram of this innovative digital receiver for the technically curious. Studying it, you can see this radio has few parts outside of the Silicon Labs' Si4734 DSP micro-chip. See the accompanying photo in the FILTERS AND SELECTIVITY section showing the radio disassembled and you will see what I mean.

SETUP

The radio requires 3 AA batteries, like my Grundig YB 300PE. Battery level is displayed on the screen as it is for the PL-600, and is accurate for either NiMH batteries (~1.2 volts) or standard alkalines (~1.5 volts). A simple key press toggles the display between alkaline or NiMH so that your current battery level reads accurately. The NiMH batteries are chargeable right in the radio using the USB adapter cabled to a computer. Charging automatically shuts off when finished. Battery consumption is very low, and batteries should last a long time especially if headphones are used.

Anon-co checks out each radio before shipping to make sure they work, a nice service. The radio also came preset for the North American mediumwave split, 10 KHz. Again, a simple key press toggles between 10 KHz and 9 KHz splits. The long wave band (153 KHz - 513 KHz) was already activated too, and can be activated or deactivated by key press.

The clock is easily set by a combination of a key press and rotation of the tuning dial, done while the radio is off. 12 or 24 hour formats are available. The clock can be made to show while the radio is in operation if desired.

No other setup was required.

QUALITY AND ERGONOMICS

The PL-380 build and fit quality is excellent, and better than the PL-600. The telescoping whip antenna measures 19-1/2 inches when fully extended, and is stout and of nice quality.

Buttons, though small, give a nice solid click when pressed, and have a stiff spring behind them. A somewhat loud tone is also emitted for each button press, but is easily silenced by a simple key action. Unlike the PL-600, lettering on the radio's buttons is on top of each button itself and it will be interesting to see at what age and usage the lettering begins to wear. The keypad is layed out in correct telephone pad-style format, with the zero key at the bottom center. Brilliantly, there are no tedious menus to wade through when changing core radio settings. Simple 2nd function key presses accomplish this. Excellent design.

A small (1-3/4 inch) front-firing, round speaker is on the left front. Sound through the small speaker is trebley at best. Use headphones, this is not a boom box.

The left side of the radio has a headphone jack and a 5 volt DC input connector, the connector being like those found on many digital cameras. Curious. I'm not sure how you would hook it to another 5 volt power source other than a computer, though a cable from an old digital camera could be stripped and cobbled up.

Two ridged, thumb-wheeled styled knobs protrude edge-wise from the right side of the radio. They are tuning and volume. They each have stepped-detents and seem a bit delicate. Be gentle when using them. I have seen one report in the Yahoo Ultralight group where a user's tuning wheel broke loose off its shaft.

On the back of the radio is a flip stand for elevating the PL-380 if set on a flat surface. The PL-380 also comes with a handstrap. The battery compartment cover is not hinged, but removable, and could be easily misplaced.

THE LCD DISPLAY

The display is clear and easy to read, and contrast is good. Backlighting is yellow, with perhaps a tinge of green, like the PL-600. It can be activated at any time by a key press, or turned on or off permanently.

A key lock button can be pressed to lock all controls on the radio. When locked, a small key is displayed on the LCD.

By pressing the Display button, found just under the Power button, the clock, alarm time, temperature, or received signal strength indicators can be made to show in turn along with the tuned frequency. Stop at the one you wish to be continually displayed.

The clock and alarm read in hours and minutes only, no seconds. A single timer is available which can activate the radio for up to 90 minutes when the alarm is triggered. You can also set the alarm to produce a buzzer-like sound.

A sleep function can turn off the radio after up to 120 minutes. By default, on first power up the radio starts in sleep mode and will play for 30 minutes before shutting off. A "30" will show on the display for the first few seconds. This can be defeated by a key press so the radio stays on permanently after power up.

Temperature reads in either Fahrenheit or Celsius. Cleverly, the software tests the mediumwave split you have selected (9 KHz or 10 KHz), and displays Fahrenheit if you have chosen the 10 KHz split or Celsius for the 9 KHz split.

For the longwave, mediumwave and shortwave bands, received frequency is displayed in kilohertz. For the FM band, received frequency is displayed in megahertz.

Memory operations are displayed in the received signal strength indicator area, at the upper right.

The PL-380, like the other ultralights using the innovative Silicon Labs' Si4734 DSP micro-chip, has a unique signal strength indicator display, the likes of which old radio buffs like me would never have dreamed possible back in the 1950s and 1960s during the waning era of vacuum tubes and analog signal strength meters. Learning of this when the Grundig G8 Traveller and Tecsun PL-300 came out, I was very excited to one day see this in action in addition to wanting to move along and try these new designs. I avoided these initial production attempts due to the so-called soft-mute issues inherent with their design software. The PL-380 has toned down the soft-mute attenuation. But more on that later.

THE RSSI AND SNR DISPLAY

When the PL-380 is tuned to the center carrier frequency of a broadcast station, the carrier strength in dBµV (dB above 1 microvolt) and the signal (+noise) to noise ratio in dB is displayed in the upper right corner of the LCD display. These are commonly called the RSSI (Received Signal Strength Indicator) and the SNR (Signal to Noise Ratio), respectively. The RSSI figure displayed is relative of course, and should not be confused with any published figures of signal strength like those available from V-Soft Communications, or seriously compared with private calculations for receivable stations in your area. Actual received signal strength is highly dependent on local terrain, daylight/nighttime conditions, transmitter antenna pattern gain, receiver antenna, ground conductivity, and other factors which make it impossible to accurately fix through calculation.

It is important to note that the RSSI indicator (marked dBµ on the display) is not the same measurement as dBu, the figure commonly used in recent years by the FCC for measuring electric field intensity of AM broadcast stations at prescribed distances. dBu [lowercase "u"] is electric field intensity, always in decibels above one microvolt/meter (and the same as dBµV/m). dBµV, on the other hand, using the Greek letter µ ["mu"] instead of u, is voltage expressed in dB above one microvolt into a specific load impedance, commonly 50 ohms. The PL-380 measures and displays dBµV, not dBu-dBµV/m.

Signal to Noise Ratio (SNR) is the ratio of (a) the power of the desired signal plus the noise to (b) the power of the noise. The (S+N)/N ratio is usually expressed in dB.

RSSI indications, as displayed on the PL-380, can range from 15 to 63 dBµV. Per Scott Willingham, one of the Si4734's designers, "The RSSI readings are referred to the pins of the chip, which are the inputs to the LNA. In the Tecsun radios operating in the MW band, this is also the voltage across the loopstick. In SW bands, the Tecsun ULRs use a preamp/LNA on the circuit board between the whip antenna and the Si4734. In that case, the RSSI readings reflect the signal at the output of Tecsun's external LNA."

Displayed SNR indications can range from 0 to 25 dB. About SNR measurements, Scott Willingham related that, "The SNR figure is calculated by a proprietary DSP algorithm, and neither the RSSI nor audio output directly play a role. The input to the algorithm is the filtered IF signal before audio demodulation. It is really more of a carrier-to-noise ratio than directly an audio noise measurement. Obviously, in AM it is bounded between 0 and 25 dB. The motive for computing and providing the number comes from implementing better station search capabilities; the display is just a nice byproduct."

At 0 dB SNR, a weak signal at best, soft-mute is at maximum attenuation according to the Si4734 programming manual. A great discussion thread on PL-380 soft-mute exists on the Yahoo Ultralight group.

Soft-mute, a further lowering of the audio level of the received signal when it drops below a prescribed strength, is undoubtedly meant to provide a more comfortable listening experience for the casual listener and not the DXer. The idea is to relieve the listener from all that nasty low level "static" and "interference", or as Silicon Labs states: "The soft-mute feature is available to attenuate the audio outputs and minimize audible noise in very weak signal conditions."

Long suffer the mediumwave DXer, as static and interference and low level signals are his bread and butter and the secret to gaining new DX. Luckily for him a weakly received signal is still there, though attenuated, and may in fact be perfectly readable if not for the soft-mute. How do we recover it?

A general consensus indicates that tuning 1 or 2 KHz off frequency and advancing the volume control will compensate for the muted audio. This is the theory: When you tune off the center frequency of the carrier it causes the signal to noise ratio to drop to zero (in fact it does), and the software responds by fully engaging the soft-mute, stabilizing any pumping audio possibly caused by multiple and different strength stations on the same frequency. At that point the volume is manually raised to counteract the soft-mute reduction.

Sometimes it works. Sometimes not, in my experience. Raising the volume also raises the background noise level and sometimes I don't see any beneficial signal recovery. Many times I have found if you stay tuned on frequency, wait a few seconds and rotate the radio around a bit to either peak the desired signal or null the offending one, the soft-mute seems to settle down and disengage, allowing reception of the weak signal. So try this too.

Maximum soft-mute attenuation for the PL-380 is 6 dB. As measured, the soft-mute threshold is actually 3 dB (SNR reading) and the slope is 2 dB/dB. This means that there is no soft-mute effect at all for SNR readings of 3 dB or more. Below 3 dB SNR, the audio is attenuated 2 dB for every dB decrease in SNR, up to a maximum of 6 dB when SNR reaches its minimum reported value of 0 dB, as such:

3 dB SNR: 0 dB audio attenuation (the threshold)
2 dB SNR: 2 dB audio attenuation
1 dB SNR: 4 dB audio attenuation
0 dB SNR: 6 dB audio attenuation

On a separate issue, a different person in the same group reported a generally high and somewhat constant RSSI value (dBµV) across segments of the mediumwave band. I have noticed the same effect here in the general frequency neighborhood (let's say plus or minus 40-50 KHz) of the local powerhouse stations, where RSSI values will hang at a value of perhaps 20-40 dBµV with an SNR of 0. I can only attribute this to a kind of front end "desense", ahead of the filtering, as I don't know what else might cause it. When you get far enough away in frequency from the overly-strong signals, the effect vanishes.

The RSSI and SNR displays update every two seconds, however the radio itself responds to realtime changes much faster than this. For example, when rotating the radio to null a station's signal, you may notice that soft-mute kicks in before the SNR display reaches 2 dB. This is because the display has not reached its update cycle yet. This is not a problem, but just something to be aware of if you are using the displays for positioning the radio.

ANTENNAS

The PL-380 employs a rather short ferrite bar antenna (3-1/8 inches in length) for the LW and MW band frequencies. FM and shortwave employ the telescopic whip antenna. Signal nulling is excellent and as good as any radio I own, as good or better than the renowned WRX911.

Interestingly, WRX911 nulling was improved dramatically here by the removal of the telescopic whip antenna's connection to the circuit board which was found to be interacting with its ferrite loop and worsening its ultimate nulling capability. Per the block diagram, the PL-380 also connects its whip to the AM tank circuit, as the AM side of the Si4734 chip is also used for shortwave AM tuning. The connection is made through a so called "SW LPF" (low pass filter), funneling the shortwave band signals to the AM tank circuit. I wondered if there would be interaction with the whip causing a degradation of mediumwave nulling and maybe some false "signal enhancement".

I did an experiment by taking the PL-380 outside away from household noise and attaching about ten feet of wire to the telescoping whip. Tuning to distant outlet WGY-810 in Schenectady, NY (186.3 miles distant), the signal to noise ratio (and audible signal strength) increased by a factor of 7 dB when the wire was attached to the whip versus when it was not. It seems there is at least some interaction between the whip and mediumwave reception, as was the case with the WRX911. In the case of the PL-380, however, even with the whip extended a full 19-1/2 inches it is probably minimal, a matter of a couple of dB and hardly noticeable.

Further, coupling this unit to a passive loop to enhance sensitivity is a rather strange experience, and unlike any other ultralight or other radio I own. Passive loops seemed to tune rather broadly, making it a bit difficult to find a signal peak. Loose coupling seems to work best, and finding the "sweet spot" of best signal transfer is difficult.

My homemade Q-Stick device, the 4-Inch Tunable Ferrite Bar featured on RADIO-TIMETRAVELLER last September, couples even more poorly than the passive loop does to the PL-380. Again, in close proximity, tuning is upset and even more skewed and undefined. I often can't find a signal peak at all when tuning the external ferrite bar. All in all, the PL-380 exhibits some strange coupling tendencies. You will have to experiment with your passive loop or ferrite tuning device to see what works best for you.

Reports in the Yahoo Ultralight group suggest that Tecsun has tweaked the stock AVC for the Si4734 chip so much that it results in "unvarying volume over many conditions", which in turn makes it hard to determine a signal peak when coupling to passive devices. See this discussion.

SENSITIVITY

The sensitivity of the PL-380 is good and markedly better than my little Sangean DT-400W ultralight. It approaches the PL-600's sensitivity throughout the mediumwave band, though it tends to be down a little more at the lower end. Reports speak of the low tank coil inductance as curbing sensitivity on this unit, particularly at the lower frequencies. Ranking four radios for sensitivity, arbitrarily ranking the Kaito 1103 at a ten since it is the most sensitive, they would rank thusly:

Kaito 1103: 10.0
PL-600: 9.5
PL-380: 8.0
DT-400W: 4.5

The PL-310, on the other hand, a previously manufactured DSP ultralight receiver using the same Si4734 chip, had a longer loopstick and better sensitivity than the PL-380, as witnessed by others. Unfortunately, reports of its heavy soft-mute signal attenuation have steered me away from it.

So what to do if you want more sensitivity? Short of using a cranky passive loop or Q-Stick device, the answer for improved sensitivity seems to be hacking into the unit and replacing the PL-380's ferrite bar with something longer and tuned correctly. This has been hashed about in many posts in the Yahoo Ultralight group. A 7.5 inch ferrite bar has been used with very good results.

All-in-all, I don't find the PL-380's sensitivity that bad. It is certainly not dead, and better than many other ultralight receivers. It is obviously no Kaito 1103 or even a Tecsun PL-600, but it can hold its own with many others.

Get up early some morning just before sun up and take the PL-380 outside and away from household noise. Put your headphones on. You will find a world of distant DX stations fighting with each other for dominance on nearly every channel. And better yet, use the 2 and 1 KHz filters to slice that interference and IBOC nastiness out of existence.

TUNING

No chuffing or dropout is apparent when tuning the radio, and tuning is very smooth once you get used to the detents on the tuning dial. The days of chuffing and signal masking while tuning are about gone for digital radios, I hope.

Two tuning speeds are available, slow and fast. They are as follows:

Longwave/slow: 1 KHz per detent
Longwave/fast: 9 KHz per detent

Mediumwave/slow: 1 KHz per detent
Mediumwave/fast: 9 or 10 KHz per detent, depending on split

Shortwave/slow: 1 KHz per detent
Shortwave/fast: 5 KHz per detent

FM/slow: 10 KHz per detent
FM/fast: 100 KHz per detent

Slow or fast tuning speed kicks in automatically depending on how fast you spin the tuning wheel. It takes some getting used to, to get the feel for how fast you can spin the tuning dial before the radio goes into fast tuning mode. It is annoying at first and will catch you off guard till you learn the feel.

Direct entry tuning couldn't be easier. Punch in a frequency, like 8-5-0, and it instantly tunes to 850 KHz without having to press an additional "enter" key, or a "period" key twice. Such a simple feature makes a huge difference. Kaito, Eton, are you listening?

General shortwave band selection is done by the "carousel" method. Press the "up" or "down" arrow keys to take you to the band you desire. Or, just punch in the frequency on the number pad once you have arrived on a shortwave band. It is simplicity at its best.

The PL-380 has several different scanning modes. See the MEMORIES AND SCANNING section for a further description.

FILTERS AND SELECTIVITY

Selectivity is nothing short of astonishing on this little radio. Five selectivity widths are available, digitally filtered of course - 6 KHz, 4 KHz, 3 KHz, 2 KHz, and 1 KHz. Gone are the days of ceramic filters, good. The AM Bandwidth button at lower left controls the filter setting using a carousel type method.

Audio recovery of weakly received signals is excellent and intelligible even in the 1 KHz bandwidth setting of the filter. And the benefit of using the lower bandwidths of 2 and 1 KHz are better signal to noise ratio, thus better signal recovery when receiving weak DX. I have tuned signals with this radio that were very weak but perfectly intelligible in the 1 KHz setting when they were not apparent in either the 4 or 6 KHz filter settings. So use the 1 or 2 KHz filter width when scanning for weak DX.

Offset tuning can sometimes be used to pull in a weak station that can't otherwise be received on frequency, perhaps due to adjacent channel interference or muddled audio. Switch to the 1 KHz or 2 KHz filter and detune the station by 1 or 2 KHz. The audio will brighten, usually imparting better clarity. Raise the volume some, to counteract the soft-mute. There are few receivers that I have known which can carry off intelligible audio at such narrow filter widths. The PL-380 can.

AUDIO

Audio quality is fair with the speaker and good using headphones. Don't expect to set this radio on a garden table and get yard-filling, full range volume. Use your boom box for that. Headphones are the key. They are the DXer's choice.

MEMORIES AND SCANNING

The PL-380 has 550 memories. Longwave, mediumwave, and FM each have 100. Shortwave has 250. Memory operation is simple. Tune to a station, press the memory key (VM), press again to reconfirm and store. Use the tuning wheel to scroll through memory slots when in memory mode.

Easy Tuning Mode (ETM) is an automated band scan type of operation which automatically scans and stores receivable channels into the Easy Tuning Mode memory, separate from regular memory. The manual states that the longwave, mediumwave, and FM bands have a total of 100 storage slots, and shortwave 250. While in the band of your choice, hold the ETM button down until the scan starts. Stations above a prescribed strength will be saved in ETM memory. A handy function, but almost identical to ATS, below.

Auto Tuning Storage (ATS) automatically scans and stores stations just like Easy Tuning Mode does, only uses regular memory. Makes me wonder why they even included ETM as another scan type operation. The difference appears to be that you have a full range of 100 memory slots for each band (longwave, mediumwave, FM) versus 100 total. Shortwave is the same, at 250.

Scanning within any band is simple, and fairly effective, though the lock thresholds are set a bit high. Press the VF key to start/stop.

Memory scanning is also available through the VM key.

SIGNAL SPURS AND IMAGES

As noted by others, the PL-380 has some spurs. The one usually reported is the strong one, a 2 KHz heterodyne on 620 KHz. I found numerous other heterodynes of low to medium strength on 560, 820, 850, 880, 920, 1010, 1280, 1420, 1430, and 1570 KHz.

Also, I'm hearing some sort of broad digital hash between 570 and 580 KHz, and a strange digital mixture fighting with a weak station on 590 KHz.

I have not detected any images in the MW broadcast band.

NOISE IMMUNITY

The PL-380's LCD display is fairly clean. Touching the display produces a barely perceptible amount of digital hash, about the same as the Tecsun PL-600. The Sangean DT-400W produces a noticeable amount of hash when you touch the digital display with your thumb.

RFI susceptibility is about the same for the three radios. Moving the radio about the house near sources of RFI produced the usual buzz in all. A computer will introduce a sizable amount of digital hash into all three radios.

THE PL-380 IN USE

As stated, the PL-380's sensitivity approaches the PL-600's throughout the mediumwave band. However, you will never notice it by hurriedly flipping through the band. If you take your time in tuning, use the narrow filters, rotate your radio and allow soft-mute to settle down and disengage, you may be as pleasantly surprised as I was.

First, let me say that sensitivity comparisons were done near mid-day to avoid any enhanced nighttime propagation.

At the high end of the MW band, usually weak CHTO-1690, Greek Multicultural Radio Toronto (1KW at 98.4 miles), is perfectly receivable on the PL-380, and about equal to the PL-600. Conditions on this one vary greatly throughout the day. I have had occasion where the PL-380 had the stronger signal by a small margin.

At the low end of the MW band, CIAO-530, Brampton, Ontario (1KW at 120.1 miles) is weak but readable, and the PL-600 excels here. WJR-760, Detroit, MI (50KW at 286.2 miles) is barely readable, but above the noise, a good catch for an ultralight without help from a passive loop. Neither the 530 KHz or 1690 KHz channel (let alone WJR-760) can be received at all on the Sangean DT-400W ultralight without help from a passive loop.

Nulling signals on this receiver can be an interesting experience if the station's signal strength at maximum null results in an SNR of 2 dB or less. At the 2 dB threshold the soft-mute kicks in and the signal drops off most abruptly, giving a false sense of having nulled the signal. Keep your eye on the SNR display when nulling, or tune 1 or 2 KHz off frequency, turn the volume up and null again, listening for the center of the fade. Remember, the SNR display may lag a little before it catches up.

Now for the selectivity test. A major problem here is local station WYSL-1040, which beams a whopping 20KW daytime signal in here with a level of some ~76 dBu - the strongest signal on the MW band here at the farm. With an antenna pattern pointed roughly northward, at some 4.25 dB gain in that direction, its effective radiated power is equivalent to some 53 kilowatts aimed right at me, and less than five miles away. It literally overwhelms receivers plus or minus 20-30 KHz either side of its frequency.

CP24 Radio 1050 (KHz), Toronto, Canada (50KW, ex-CHUM), across Lake Ontario, a distance of 105.0 miles, is the only station even capable of putting a up a fight with WYSL. All the rest are either too weak or too distant. I can usually detect the presence of CP24 in the WYSL splatter with the PL-600 using the narrow filter (4 KHz), however identification is difficult to impossible. Using the PL-380 and nulling WYSL carefully, it is perfectly readable using the 2 KHz and 1 KHz filters. This is an astonishing feat which impressed me very much!

SUMMATION

The Tecsun PL-380 is a technological wonder in a small package, and all for $45.99 + shipping. It is an experimenter's playground if you are into high technology, and a keeper for me.

Sensitivity is adequate in my opinion, and if you are patient with a passive loop it can make a positive difference. Remember, overall it is no Tecsun PL-600 or Kaito 1103 in the sensitivity department, but it is way ahead of a lot of other standard ultralights.

Selectivity is unmatched, perhaps in any radio under $1000 except for other Si4734-based receivers. Nulling is excellent. Audio is good. Ergonomics are simple, and the receiver is easy to use without tedious menus to navigate. 550 memories, not that you will use them, but they are available.

Four different scanning options. Two tuning speeds, and a real volume control. The display is bright and easy to read. If I could change a couple of things, I would add some up and down frequency slew buttons and perhaps beef up the tuning dial to be more like the PL-600 or Kaito 1103, getting rid of the detent. The detent is fine for the volume control.

Soft-mute is at a minimum in this radio, and I didn't find it objectionable once I got used to it. 6 dB of audio reduction is not a lot and can be defeated with some finessing of the radio, making it a non-issue in my opinion.

The radio has a fair amount of spurs, and some digital hash on a couple of channels. These are annoying. This is not the cleanest radio.

All-in-all, the PL-380 may be the ultimate ultralight receiver as of this writing, and a competitor to some larger models for mediumwave reception. The first company that produces a radio using this Si4734 chip with the soft-mute defeated, the thresholds lowered, AVC adjusted, and includes a matched, 6 to 8 inch ferrite rod is going to have a real DX machine on their hands.

LINKS

For the technically curious, an excellent treatise on calculations and measurement of electric field intensity, received voltage, and power density, see:

Calculations and Measurement

A excellent description of signal to noise ratio can be found here:

Signal to Noise Ratio

RADIO-TIMETRAVELLER

Dead Air on 1040 KHz Brings Daytime DX

2010-06-05T10:33:00.008-04:00

A belated story from Sunday, May 23.

Tuning across the MW broadcast band with the Tecsun PL-600 early Sunday afternoon, I discovered local powerhouse station WYSL-1040 (20KW, 4.9 miles distant) off the air for some reason. What an opportunity! WYSL normally overloads the receivers here plus or minus 20 to 30 KHz either side of 1040. I grabbed the 24-inch loop and headed for the backyard away from household noise to see what I could hear on 1040 KHz and adjacent frequencies.

20 KHz up, across the Appalachians and coming in nicely with good strength was KYW-1060, Philadelphia, PA (50KW) at a distance of 232.0 miles.

Stronger yet, 10 KHz down on 1050 KHz was CP24 Radio 1050, Toronto, Canada (50KW, ex-CHUM), across Lake Ontario, a distance of 105.0 miles. Approximately 50 miles of this distance is over water, giving a certain amount of signal enhancement due to the lower path loss. On a good day I have heard this station in the spill-over of WYSL with a narrow filter. This signal enhancement axiom seems to be true of all signals coming across the Great Lakes, from Montreal at the east end of Lake Ontario to WJR-760, Detroit, MI, clear across the west end of Lake Erie, nearly 300 miles distant.

On 1040 KHz itself was an ESPN Radio station, at least it was identifying as such. It appeared to be in the New York City area from the talk heard, and at good signal strength. Although they never did give their call letters, the odd thing was that they identified their frequency as 1050 KHz on several occasions! One possibility exists here in that the station might be WEPN-1040 (50KW), 238.6 miles, out of New York City. It is an ESPN Radio station. Very weird that it should identify as transmitting on 1050 KHz when it was most definitely on 1040 KHz. I even had to check the dial several times to make sure I was correct on this.

1030 KHz was vacant, not totally surprising. The only two possibilities here would be WWGB, Indian Head, MD (50KW) at 304.5 miles, and WNJE, Flemington, NJ (15KW) at 217.7 miles, but neither was making the grade. WBZ-1030, Boston, MA (50KW), has a regular appearance at night when WYSL switches to lower power.

Tuning down another 10 KHz, pointing the loop south brought in the obvious in KDKA-1020, Pittsburgh, PA (50KW), at a distance of 200.9 miles with good signal. This oldtimer also comes in well at night after WYSL switches to lower power.

Local WYSL-1040 puts in a daytime 20KW signal here in the neighborhood of ~76 dBu and is the strongest signal on the MW band here at the farm. With an antenna pattern pointed roughly northward, at some 4.25 dB gain in that direction, its effective radiated power is equivalent to some 53 kilowatts aimed right at me, and less than five miles away. WYSL also runs critical hours and nighttime power levels of 13.2KW and 500 watts respectively. Even at the 13.2 KW level during critical hours, its signal is a whopping ~74 dBu. The next closest contender, WHAM-1180 in Rochester, NY (50KW), at 11.2 miles distant, booms in here at some ~64 dBu.

By the way, all the distant stations documented above were also received on the Sangean DT-400W ultralight. With the Tecsun PL-380 just arriving yesterday, it will be interesting to see how it performs in tests against these two powerhouse stations.

Tecsun PL-600 Holding Interest, PL-380 On The Way

2010-05-21T14:16:00.014-04:00

Despite up and down reviews, there seems to be continued interest in this receiver, worldwide. Many people have downloaded the Tecsun PL-600 review and schematics featured last August on RADIO-TIMETRAVELLER. The combined download totals for both are nearing the 2,000 mark as of this writing, some 9 months later. Surprisingly, daily downloads are still averaging about 6 per day. Though some negative press is out there, interest remains, and deservedly so in my opinion. With the new DSP radios coming out, month by month, I'm interested to see at what point they start to take over the old style PLL digitals. Most that I've heard of have been ultralight-sized. Perhaps soon we will see some larger units on the market.

In case you couldn't tell, I still love my PL-600. Outside of the ultralight category, it continues to be my receiver of choice for casual and serious MW DXing, for several reasons. Size-wise, its portability is just right as opposed to my rather large (albeit excellent) Eton E1, which sits in a drawer right now. It has been totally reliable for the last year (my Kaito 1103 developed a firmware glitch in its first year), and performed admirably throughout my winter in the desert southwest. It suffered bumps and bangs and desert dust, but captured much DX, including Japanese MW stations on numerous occasions, and barefoot too. The radio has great ergonomics and firmware. It is a fun radio to use.

Kudos to the ergonomic-designers of this radio. Punch in a frequency, like 8-5-0, and it instantly tunes to 850 KHz without having to press an additional "enter" key, or a "period" key twice. Such a simple feature makes a huge difference. Easily coded in firmware at design-time, it seems to be missing from many of today's digital receivers. The PL-600 is also a great little receiver to take to bed at night with headphones on, to see what the sunset greyline will bring in. With careful nulling, I have heard KOA-850, Denver, CO this way at their sunset, 1420 miles distant, rising above the QRM of four other east coast stations within 500 miles. Again, this is with a barefoot PL-600.

Harsh audio in the AM mode is still the drawback for a lot of people, and continues to be mentioned in the critiques. I don't find it as objectionable as some, though I too have found it annoying at times as it seems to come and go with different signal levels. KB5AG's resistor mod is supposed to cure this malady, getting rid of the AM distortion. (2K resistor from pin 18 of audio IC to ground). I will try this soon.

Amazon is still selling the Tecsun PL-600 for $79.99 through the Kaito distributor.

Considered by some a better, or at least a comparable radio, Amazon is also still handling the Kaito 1103. Price: $89.99.

It will be interesting to see how long the Tecsun PL-600 and the Kaito 1103 last in the marketplace. An older radio by a couple of years, the 1103 continues to be a good seller, though I have a hard time understanding why it has remained so. Its sensitivity and audio are good, build quality is good, but the ergonomics absolutely horrible - including a pointless LCD sliderule dial face that takes up nearly the entire front of the radio which could be better used for something constructive. We shall see.

Sadly (??), the Eton E1 (see my review) has recently been discontinued by Universal Radio. Too much money ($400 for the stripped model), quality control problems early on, an atrociously low-contrast and volatile LCD display, and a shortwave radio broadcasting medium which continues to vaporize before our eyes have sealed its overpriced fate.

Wanting to move along and try new designs, I have avoided the newest Grundig offerings, the G3 and G6 because of so-so reviews, and the G5, supposedly just a Degen/Kaito 1103 with better ergonomics. I've been itching to try one of the new DSP ultralights and have watched them evolve since the Grundig G8/PL-300 came out. The new Tecsun PL-380 (see my subsequent review) seems to have corrected the audio muting problems inherent with the earlier units, so I've ordered one from eBay seller anon-co. It is in transit from Hong Kong this very day. I'll be playing with that soon and reporting what I hear. It will be interesting to see how it performs receiving weak signals up against local 50KW and 20KW powerhouse stations WHAM and WYSL.

Another Deal, The Panasonic RF-565

2010-05-19T13:40:00.003-04:00

Last Sunday's flea market jaunt brought another great bargain. There, sitting on a table in the sun was a Panasonic RF-565 amongst some other junk. Price: $1. It was dusty, its aluminum trim was dull. But nothing seemed broken, and the telescoping whip was still intact and straight. The dial mechanism felt tight and worked well. The volume control was intact, and not loose. There are possibilities here, I thought.

This little portable was built in the late 1960s and has a 3-inch loopstick MW antenna, ten transistors, and a little two inch speaker. It is battery operated off of four AA cells, but it also has the ability to run off the 110 volt mains. Forgetting my spare batteries to try it out, I forked over a one dollar bill and headed home with fingers crossed.

First off, to plug it into the 110 volt service. It works! Volume control was very scratchy. Tuning fine. AM stations came in across the dial, not strong, but I am inside a house with a lot of line noise. I opened the battery compartment. The battery holder was intact. One of the springs had a little bit of rust on it, easily fixable. Using a Phillips screwdriver, I pulled the back off the unit. It was very clean inside, a surprise. This unit was made to be serviced, as both the whip antenna connection and battery holder connections were unpluggable from the main board.

I gave the volume control a shot of cleaner, including the slide switches. Replacing the back, I then cleaned the rusted battery spring, and installed four fresh AA batteries. Switching the front panel switch to battery power, I turned on the '565. Volume control and switches now operated static-free.

Sensitivity on the RF-565 is good, better than average. Nulling is poor, and most of my ultralights have better nulling ability for some reason. Complete with tone control switch, plenty of sound is available out of the little speaker. And it even has a headphone jack. The AM band only covers 540 KHz to 1610 KHz, so the x-band will not be usable on this radio. No matter. This will be a great little portable to take to the beach or the mountains camping.

Viva Flea Markets

2010-05-15T12:15:00.006-04:00

That time of the year is upon us again here in the northeast. The weather is turning nicer, everything is in bloom or leafing out. And it is the season of outdoor flea markets.

I'm always on the lookout for radio gear at these events, particularly older pocket, portable, or table top transistors radios of yesteryear. Often they can be had for a song. Analog rules the day here. Dial strings and pulleys for table tops, direct drive to the main tuning capacitor for smaller transistor units. The shape they are in varies of course, though I find many are in acceptable or even fairly good shape. Volume controls are normally scratchy, but easily cleaned up with electronic cleaner. Reception on these units is marginal sometimes, as many of the older transistor units were not noted for extreme sensitivity. But do they work? I have been burned on more than one occasion by trusting a vendor's "Sure it works!" proclamation. Now, as a rule, I take along a set of AA batteries or a 9 volt unit so I can try out the DC-powered radios. The plug-in units you just have to trust.

Recently, I picked up a 25 year old Radio Shack MTA-16 transistorized table top radio. The price? An astoundingly low $2. It was in excellent shape, with the only blemish being three small white paint spots on the cabinet. I see several of these same units bidding right now in the $16-20 range on eBay.

I brought it home and plugged it in. Voila! It worked! The dial string was fairly tight, and band calibration was suitable. Tuning was a little bit touchy on weak stations, as there is just a tiny bit of slop in the dial. Not a problem. Sensitivity was about medium. WWKB-1520 in Buffalo, NY comes in wonderfully at 60 miles distant, with room-filling volume from the 4-inch speaker. The radio even has a tone control. And a bonus - it covers the full mediumwave band from 540 - 1700 KHz.

The MTA-16 uses a 3-inch loopstick for an antenna versus a wound-wire loop antenna on the backboard, a plus. This means it will be less effected by computer-generated RF noise in the receiving shack. Many of the older table tops, particularly the vacuum tube types, had that wire loop antenna, and it was very susceptible to RF and digital hash. Should I ever get into FM DXing, the MTA-16 even has a 300 ohm connection for an FM band antenna.

The MTA-16 now commands a prominent position on the shelf behind my computer. I listen to it while working on computer projects. Lately I've been thrashing through FCC mediumwave data, and the radio has provided a lot of enjoyment.

Check out some flea markets, or yard sales, or garage sales this spring and summer. You might be surprised what you find.

Radio Silence

2010-04-29T10:47:00.003-04:00

Continuing with the search for official government sources of current AM stations on (or off!) the air, I uncovered this gem the other day on the FCC site.

AM silent stations, silent over 2 months

This is a list of U.S. stations which are licensed but silent and off the air for at least two months. As of this writing, the count is nearly 100. And good news, the list seems to be updated regularly. Unfortunately, Canadian and Mexican stations do not appear because this information is not added to their records within the FCC database.

Additionally, this and other useful information like MW stations broadcasting in hybrid IBOC digital format can be garnered from this FCC search page.

This will be helpful information for merging into an overall database.

Canadian/Mexican AM Station Search

2010-04-28T16:42:00.011-04:00

Recently I have been browsing the web looking for official government sources of current Canadian and Mexican AM stations on the air. Accurate information on who is actually broadcasting is hard to come by in one comprehensive database.

CAN THE FCC HELP?

Here in the United States, the FCC's official government database covers not only US stations but Canadian and Mexican stations as well. Web opinion portrays it as notoriously flawed. Part of the problem, I believe, is that the output of the AM Query list is drawn and built from a number of separate databases, many of which have multiple and redundant records for the same station. "Application", "In-Planning", various types of "Construction Permit" records and "Licensed" records, and a smattering of "Deleted" records exist. The FCC saves everything. Slogging through them and deciding which is current and which is not is nearly impossible, even for the FCC. It is a case of too much information. Spending many months weeding out the chaff, I have found the US section to be surprisingly accurate.

Not so for Canadian and Mexican records. They are added to the database, missing information, then forgotten. In past years, broadcasting in Canada has been moving to FM, and year by year, fewer and fewer AM stations remain. This is somewhat true for Mexico as well, and Mexico's AM to FM transition process may speed up even faster with its announcement that it plans on migrating all AM stations to FM in the near future. Deleted Canadian and Mexican stations are almost never pulled from the database. In my experience with the FCC database, some Canadian stations have been off the air for nearly twenty years and are still listed. Hence, this is what drives my search for a more up-to-date governmental database for these countries.

OH, CANADA

Similar to the FCC's AM Radio Database Query page, I discovered recently Industry Canada's Frequency Range Search page which will output MW radio station data to either a web page or downloadable text file. This information appears to be drawn from a comprehensive database of all spectrum telecommunications across Canada. For our MW interests, one must specify the search criteria, i.e., frequency range (530 KHz - 1700 KHz), and pertinent filtering fields. A multitude of information is available, such as latitude and longitude of station, transmitter power (though only available in dBW), a wealth of antenna information, site elevation, call sign and licensee names, and much more.

How accurate the Canadian government query is remains to be seen. I don't see record redundancies yet. I am hoping that they have deleted inactive station records. So far, that generally appears to be the case, though I have a report of one. A small annoyance is that tourist information stations and low power emergency stations are also included in the output. There doesn't appear to be a filter option to remove them. I'll be experimenting with this data in a program I'm writing that already uses the FCC's AM radio station data to provide comprehensive information for MW DXers like me, such as sunrise/sunset times for distant stations, distance and bearing, competing co-channel stations, relative signal strengths, and a multitude of other interesting info. Since this Canadian database appears to be more accurate than the FCC's, I'll merge it in, eliminating the inaccurate records from the American one, and hopefully provide some needed accuracy in actual stations on the air.

VIVA MEXICO

Mexico is another story. I have not been able to find an actual government database file online that documents their AM radio station network. Private sites do exist that attempt to provide lists of Mexican AM stations, but their information is not in a file format which can be read by a third party program. This is what is needed. If anyone has any information on a government site or other site which has compiled the Mexican AM station network into an accurate data file format, I would appreciate knowing its location. The only government list I found available, in .PDF form, is the Infraestructura de Estaciones de Radio AM list. Though the URL address is dated 2008, the actual .PDF retrieved is dated 31-Dic-2009, or December 31, 2009, so hopefully the information is somewhat current. Check the Cofe_radio_y_television page out for additional information.

Cross Country Pipeline - A Daytime MW DX Tale

2010-04-26T16:54:00.021-04:00

This is a story about daytime mediumwave DXing. To set up this story, let me tell you that I am on my way back to New York from Arizona, by way of Denver. As usual, I like to DX the mediumwaves on the way, often from my truck radio. There is little but routine DX until I leave Denver headed east on Monday morning, April 19th. Over the next two days I will have some new personal daytime MW DX distance records and an incredible DX experience to remember. And here is the story....

MONDAY, APRIL 19

0 MILES.
Denver, Colorado. 0900L (9AM). I am headed due east out of Denver on I-70. I-70 snakes through Colorado, Kansas, Missouri, Illinois and onward for the eastward traveller, through the major cities of Kansas City and St. Louis, crossing the Mississippi River at St. Louis. Kansas itself is 425 road miles across and Missouri about 250. The eastern plains of Colorado and west-central Kansas are about as flat as a pool table, and there are basically no trees until you near Topeka, Kansas, closing in on Kansas City, some 625 road miles distant.

To add interest to the trip, I decide to see how far I can hear three prominent Denver stations: KHOW-630 (5KW), KKZN-760 (50KW), and KOA-850 (50KW). 760 KHz and 850 KHz are clear-channel frequencies. I am DXing on a 2006 Ford Ranger truck radio. The truck radio is adequately sensitive and uses a short whip antenna.

160 MILES.
I cross the Colorado-Kansas state line, 160 miles out, about 1300L. All three Denver stations are still powering in, even lowly KHOW-630 at 5KW. No difference in strength can be discerned. Remember, it is daytime, and midday. The D-layer has long since "re-coagulated", and we are well outside the 2-1/2 hour guard zone around sunrise and sunset. It always amazes me why these extreme daytime MW DX distances are common out west, and I rarely see this happen in the east. My fellow Ham buddy Jeff, K3OHU, says it is due to all the clutter in between station and receiver that attenuates the signals. Out west are wide-open spaces. Perhaps he is right. I proceed on, as I plan on driving another 2-3 hours before stopping.

225 MILES.
I pass Goodland, Colby, and Oakley, Kansas, closing in on 300 miles now. The three stations continue to hang in, very strong. I might expect that of KKZN-760 and KOA-850, both 50KW stations, but not of KHOW-630 at 5KW.

309 MILES.
At 1530L, I pull into Hays, Kansas for the night, some 309 miles as the crow flies from Denver. KHOW-630 has weakened some, but is still of medium strength. KKZN-760 and KOA-850 are still powerhousing through the truck's speaker. Somewhere in the last hour I have crossed into the Central Time Zone, losing one hour. Tomorrow, Tuesday, should be interesting, and we shall see what and who shows up in the morning.

TUESDAY, APRIL 20

309 MILES.
Hays, Kansas. I am up at 0530L and back on the road. It will still be dark for another hour. Intermittent low fog hugs the road, mile after mile. I take a scan around the band to see what's happening. Within fifteen minutes I hear all four sides of the country - the west coast: KFI-640 Los Angeles, CA, the east coast: WSB-750 Atlanta, GA, the northern border: WCCO-830 Minneapolis, MN, and the southern border: WWL-870 New Orleans, LA. Also heard before 0630L and daylight are WGN-720 Chicago, IL, WBAP-820 Dallas TX, KEEL-710 Shreveport, LA, and KOKC-1520 Oklahoma City, OK, all with strong signals. Things are about to get interesting.

350 MILES.
East of Hays, Kansas, and still dark out, the three Denver stations are nowhere to be found, buried, I suppose, under the jumble of nighttime signals on their frequencies. It starts to get light, and I hurtle east across central Kansas, wondering if this will be the end of hearing daytime Denver DX for this trip, as I will soon be out of range.

398 MILES.
Nearing Salina, Kansas, stations to the extreme east are fading away due to the impending sunrise. WSB-750 Atlanta fades, as does WGN-720 Chicago. Popping up on 720 KHz now is a strong signal out of 50KW blowtorch KDWN, Las Vegas, NV. KFI, Los Angeles, holds its own on 640 KHz. I tune to 740 KHz looking for KCBS in San Francisco, expecting something further up the west coast, but nothing. KGO-810, San Francisco, is also absent. Next I tune to 770 KHz - the channel was vacant just a little while ago - and now there is powerhouse KKOB in Albuquerque, NM. I have a quick breakfast in Salina at 0645L, then back on the road at 0730L.

450 MILES.
East of Salina, Kansas, the sun is well up now. A pleasant surprise! Denver's KOA-850 is back in there, alone on frequency. KKZN-760 is in there too, but competing with KCCV-760 (6KW), a religious station in Overland Park, Kansas, near Kansas City. KHOW-630 has not showed.

495 MILES.
I come to Topeka, Kansas at 1020L. The low fog is lifting. It is more than 2-1/2 hours past sunrise and into the daytime DXing timeframe now, and the nighttime skip has totally vanished. KHOW-630 has still not reappeared and I suspect we are out of range for it anyway. KCCV-760 in Overland Park has overtaken Denver's KKZN-760, I figure for good, as KCCV will only get stronger as I approach Kansas City. By then, presumably KKZN will be out of range. KOA-850 hangs in there quite nicely with a nice medium strength signal all by itself.

550 MILES.
I roll through Kansas City, crossing the Missouri River, and on into the state of Missouri at 1135L. KOA-850 is still hanging strong. KKZN-760 is completely obliterated by the Overland Park station KCCV. I press onward for Columbia, Missouri, just past the center of the state, another 120 miles distant.

600 MILES.
Fifty miles inside Missouri at 1220L, the Overland Park station fades, revealing Denver's KKZN-760 again, at a good signal strength. KOA-850 continues to hang fairly strong, still alone. Surprisingly, the signal strength of these two are still respectable through the truck's speaker, and arm-chair copy. KHOW-630 is still absent. I hear a weak religious station creeping in on 630 KHz, probably KJSL-630, St. Louis (5KW), nearly 200 miles in front of me. I am getting close to my personal daytime DX record of 675 miles. Ironically, that is held by KKZN-760. I have received it twice while in southwestern Arizona.

675 MILES.
I pass through Columbia, central Missouri, at 1330L after stopping for a very quick lunch. The excitement is building, as I am now passing my daytime MW DX distance record mark of 675 miles, and I have two stations still in contention for a new record. I can hardly contain myself. To my amazement, Denver's KKZN-760 and KOA-850 are still hanging in with weak to medium signals, well above the noise level. The fades and peaks have become long and drawn out, perhaps 20 or 30 minutes between them, but even the fades are still readable. What gives? I have never heard MW DX signals at this strength at this extreme distance during the daytime. The Denver weather report on KOA indicated fog still on the ground in the Denver area at their 1130 AM local time. I start to wonder if the ground fog is part of this scenario?

685 MILES.
A few minutes go by, then bad news. I start to hear splatter on KKZN's signal. The splattering station, at 770 KHz, is playing a sort of ethnic variety music, so I assume it must be coming from station WEW-770 (reportedly 10KW), located in St. Louis, Missouri. This can only get worse as I close in on St. Louis, and I fear that in time I will lose KKZN permanently to it. To make matters worse, underneath KOA-850 another station appears, gaining in strength. I can't identify it yet.

710 MILES.
East of Columbia, and less than 100 miles from St. Louis and the Mississippi River, I decide to check for WSM-650, Nashville, Tennessee, the famous Grand Ole Opry station. This spring on my trip out it carried well into southern Missouri, down the I-44 corridor. I tune to 650 KHz. There I find a station, weak-to-medium, in the clear. I listen for ID, as the 1400L news is on but I missed the top-of-hour. They give the local weather report. Something about Wyoming and Cheyenne. What is this? No, it can't be! Then the ID comes. "This is KGAB, 650 AM, Cheyenne"!

I can't believe my ears. KGAB near Cheyenne, Wyoming transmits with a power of only 8.5 KW! But there it is with a perfectly listenable signal strength through the truck speaker at an amazing daytime distance of 710 miles! The local time is 1405 CDT, and an hour earlier at 1305 MDT in Wyoming. KGAB is totally in the clear, without side splatter or other interference on-frequency. The thought occurs to me that I'm only about 100 miles from the Mississippi River and the Illinois state line, and I begin to wonder if the two Denver stations and Cheyenne will hang in there long enough to get to the river. I race towards the Mississippi, as things are starting to deteriorate on all fronts.

738 MILES.
The stations are getting weaker. Denver's KKZN-760 is getting hit very hard with 770 KHz splatter, and is almost unreadable now. KOA-850 is almost totally covered up with co-channel interference. I identify the offending station as KFUO-850, coming closer by the mile, in Clayton (St. Louis), Missouri. Little KGAB-650 in Cheyenne, Wyoming is weak but still readable, and in the clear. The fades take it totally out, then it re-emerges for several minutes at a time. The Glen Beck program is on. It started after the news at 1400L CDT. 54 miles to the river. And one hour. I've got to do something.

I pull off the exit at Warrenton, Missouri, thinking I will attach a four foot length of wire to the truck antenna and let it trail in the wind while I drive. I've used this technique before to gain some signal strength and pull in distant DX. I attach the wire and continue on down I-70 towards St. Louis. Signals are marginally better, but the 770 KHz splatter is killing KKZN-760, and KOA-850 has finally disappeared under St. Louis's KFUO-850. Wyoming's KGAB-650 hangs in there, barely.

792 MILES.
Traffic builds as I approach the river. The only station left is KGAB-650. It is right at the noise level. At exactly 1505L I cross the Mississippi. Just over the bridge I faintly hear Glen Beck say a few words just above the noise level - what, I don't know - but I can recognize his voice. Then - gone. KGAB fades below the noise for good.

800 MILES.
I am in Illinois. To the left of me I pass two AM radio stations. One has an array of four towers and the other six. The receiver desenses so badly that it overloads. I press on wondering what will happen next.

827 MILES.
Pocahontas, Illinois. It is 1545L time. Hurriedly, I pull off the exit and into the motel parking lot where I will stay for the night. After registering, I check the truck radio again. Surprisingly, 760 KHz is clear of splatter - but nothing but noise is heard - and no KKZN. 850 KHz is occupied by St. Louis's overwhelmingly strong KFUO. Weak but steady, 650 KHz plays the country music of Nashville's WSM. KGAB-650 is gone, forever.

Quickly I grab the Tecsun PL-600 out of the truck and tune to 760 KHz. I put the headphones on. Something is there just at the noise level, but what?

In a greater hurry, I dig for the 24-inch passive loop I constructed this winter. The PL-600 is still two feet from it when the signal on 760 KHz comes right up out of the noise, nearly arm chair level in the headphones. It is Progressive Talk Radio, KKZN-760, Denver, Colorado! Unbelievable! A new personal daytime mediumwave DX record of 827 miles! Imagine hearing the front range of the Rocky Mountains - some 36 miles east of the Mississippi River in Illinois - IN THE DAYTIME!

ACTUAL COMPUTED GREAT CIRCLE DISTANCES

KKZN-760 (50KW) Denver, Colorado to Pocahontas, Illinois: 827 miles
KGAB-650 (8.5KW) Cheyenne, Wyoming to I-270 & Mississippi River: 791 miles

REFLECTION

Who knows how far into Illinois I could have heard KKZN-760? With the interference from KCCV-760 gone, its signal was still respectable off the 24-inch loop at the town of Pocahontas, some 36 road miles east of the Mississippi River. My guess is another 50-100 miles, closing in on 1000 mile daytime DX!

What makes the difference in long distance daytime DX? Clear co-channels and clear adjacent channels are very important. Flat, unobstructed terrain I'm sure is important too. Ground conductivity is very important. Ground conductivity from Denver to central Missouri ranges from 15-30 millimhos per meter. From central Missouri eastward to the Mississippi River it drops to 8, then rises back to 15 east of the Mississippi River. Did partial fog along the distance also make a difference? Possibly, but I will never know for sure what effect it had.

It is remarkable what a 24-inch tunable, passive loop will do for a signal seemingly buried in the noise at 827 miles distant. I was astounded.

THE PLAYERS: WESTERN END
KHOW-630, Denver, CO 5KW News-talk
KKZN-760, Thornton, CO (Denver) 50KW Progressive talk
KOA-850, Denver, CO 50KW News-talk
KGAB-650 Cheyenne, WY 8.5KW News-talk

THE PLAYERS: EASTERN END
KJSL-630 St. Louis, MO 5KW Religious
KCCV-760 Overland Park, KS 6KW Religious
WEW-770 St. Louis, MO Variety/ethnic music
KFUO-850, Clayton, MO (St. Louis) 5KW Religious

DXing The Shortest Days

2009-12-14T15:06:00.016-05:00

It's that time of the year again when the days are the shortest and the nights the longest. There are barely 10 hours of daylight here in southwestern Arizona, as the sun is rising at 0724L and setting at 1722L. D-layer absorption during daytime hours is at the lowest this time of year. Today, at the noon hour, I went on a little mini-DXpedition to a nearby hilltop which gave me a 360 degree view. I started DXing at 1130 local time and continued till about 1230 local.

Radios used were the Tecsun PL-600 and the unassisted truck radio. The Tecsun PL-600 was assisted with the 24-inch box loop. Here are the highlights:

660 KHz, 1130L, KTNN, Window Rock, AZ. 50KW (truck radio). Medium strength, but easy. 327 miles.

740 KHz, 1135L, KBRT, Avalon, CA (Catalina Island, "26 miles across the sea"). 10KW (PL-600 and truck radio). Strong on the truck radio and overriding KCBS, San Francisco. 239 miles.

760 KHz, 1145L, KKZN, Thornton, CO. 50KW (PL-600). 675 miles at the noon hour! Progressive Talk Radio. Signal was in and out, weaker and underneath San Diego's 50KW powerhouse KFMB. I was able to partially null KFMB using the box loop, which made the difference. Great daytime DX.

1090 KHz, 1221L, XEPRS, Rosarito, Baja California, Mexico. 50KW (PL-600). Weak, but readable, peaking to medium at times. This is Baja's XX Sports Radio, broadcasting in English to San Diego from an appreciable distance down the Baja peninsula. Studios are reportedly in San Diego. 186 miles.

1120 KHz, 1210L, XEMX, Mexicali, Baja California, Mexico. 400 watts (PL-600 and truck radio). Broadcasting oldies. 100.9 miles. Good reception for 400 watts.

Now for the amazing "pipeline" station, which always seems to put some kind of a signal into southwestern Arizona at any time of year:

700 KHz, 1225L, KALL, N. Salt Lake City, UT. 50KW (PL-600 barefoot and truck radio). 514 miles.

KALL is the amazing one, not for distance but for signal strength. Though I have heard this one before during the daytime, this time of year it seems to have a pipeline into the southwest. Signals on the unmodified truck radio were absolutely astounding. Note that the distance here is in excess of 500 miles at the exact center of the daylight period. Shown is the beautiful location of KALL's tower array.

Try some daytime DXing during this time of year, particularly near mid-day. You might be surprised at what you can hear.

WWL New Orleans Finally Logged

2009-11-29T16:56:00.003-05:00

November 25, 2009

WWL-870, New Orleans, LA (50KW) appeared this morning at 0455L (1155 UTC). The signal was weak with much phase distortion, however, it is now finally and positively logged! Received both on the Tecsun PL-600 barefoot and with the 24-inch loop.