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Saturday, December 21, 2019

Decoding Antenna Factor In Ferrite Loops

Mediumwave DXers and signal measuring enthusiasts, let's have a look at Antenna Factor and see if we can use it.

Q: What is Antenna Factor?

A: A correction factor translating arriving field strength to antenna output. Bonus: It can also be used in reverse, translating antenna output to arriving field strength.

Q: Can the mediumwave DXer with a modern portable DSP receiver use Antenna Factor to any advantage?

A: Yes, of course. You may not realize it, but you are holding a rudimentary field strength measuring device in your hand.

DEFINING ANTENNA FACTOR

Antenna factor is often greatly mis-understood. Antenna factor is the relationship between the electric field strength "E", which is the strength of the radio wave field surrounding the antenna (usually referred to in millivolts per meter) to the voltage output "V" of the antenna itself (usually measured in microvolts).


Simply, it is the ratio of the former to the latter - antenna field to antenna output - and shows the antenna's ability to convert the surrounding received field to a usable voltage. It is literally the relationship between field strength and signal strength. In the mediumwave DXer's case, "V" is the ferrite loop's voltage output - signal strength! And another bonus for us - they are directly proportional - that is, an increase in the antenna's surrounding field results in a proportional increase in the ferrite loop's voltage output.

INTERESTING POSSIBILITIES

Wouldn't it be interesting if we knew the antenna factor of our ferrite loop? Or at least its approximate value? What might we do with that? With our modern DSP chip radios displaying an RSSI (Received Signal Strength Indicator) voltage, the output of its ferrite loop, we could easily determine an approximate value of the electric field strength of the station at our location, a value right in line with the published values gotten from V-Soft Zip Signal and radio-locator, or an expensive signal measuring device.

Let's take this apart, piece by piece, and see how we can get there.

Although the field strength and antenna output measurements we talk about in the paragraphs above are voltage, antenna factor is generally expressed in "dB" microvolts per meter, or simply "dB".

The decibel (dB) unit of measurement is used to express the ratio of one value of a power or field quantity, or a voltage, to another. It is a logarithmic measurement, in that the decibel equals 10 times the common logarithm of the power ratio or 20 times the common logarithm of the voltage ratio. Remember, dB, used alone with no reference, is a ratio. 0 dB means no change, or an equal ratio.

In our case we are dealing in voltage ratios here, not power ratios, so our formula will be 20 times the common logarithm of the voltage ratio.

So, if our voltage ratio of E/V is 2 for example, or double, our dB value is 20 times the log of 2, or 6 dB. Note that a doubling of the voltage (i.e., 2) is a 6 dB improvement.

National NC-270 S-Meter

Devopedia has a great summation of the decibel if you would like to delve into it further.

Old timers will remember the analog S-meter on the old receivers. It was calibrated S-0 to S-9, then in dB above S-9. Each S-unit was a doubling of received voltage from the previous S-unit, or a 6 dB gain. Consequently, each S-unit increase is an increase by the power of 2. S-9 is 2^9 stronger than S-1, or 512 times greater signal voltage! S-9 represented 50 microvolts of receiver input measured right at the antenna - signal strength. Thus the S-meter was commonly called a signal strength meter. Be sure not to confuse field strength with signal strength. Field strength is the electromagnetic field surrounding an antenna and signal strength is the converted voltage at the antenna output.

Now, what about ferrite loops and frequency dependence? Many will recognize that their radio might be a little more sensitive at one end of the band than the other. At one given frequency, for all stations received on that frequency, the relationship between their field surrounding the antenna and the output voltage of our field converter (our ferrite loop) is constant. This being so, the antenna factor is also a constant for all at that given frequency. It may be slightly different at a different frequency as we will see.

RSSI - 19 dBµV

So by knowing the antenna factor and the RSSI voltage we can work in reverse to determine the field strength at the antenna. The antenna factor (in dB microvolts per meter) can simply be added to the value of voltage measured (in dBµV) at the ferrite antenna output! It is a simple matter then to convert that antenna factor dB value back to a field voltage in millivolts or microvolts per meter.

What are the two values dB microvolts per meter (dBµV/m) and dBµV telling us? A ratio, that's all. It's the amount of field or voltage compared to one millionth of a volt (the "µ", or "micro", means one millionth).

FIGURING ANTENNA FACTOR FOR OUR RADIO

The three pieces of information are:

  1. E - Field strength of the radio station's signal at the antenna (in dBµV/m).
  2. AF - Antenna factor of our antenna (our ferrite loop), in dB/m.
  3. V - Voltage output of our ferrite loop (the RSSI reading in dBµV).

Our formula for determining antenna factor AF is this:

                              AF(dB/m) = 20 * LOG(E/V)

                              Note: E and V must be in the same units - voltage!
                         
Our formula for determining field strength E is then this:

                              E(dBµV/m) = V(in dBµV) + AF(dB/m)

Our formula for determining signal strength V (RSSI) is then this:

                              V(dBµV) = E(dBµV/m) - AF(dB/m)

Knowing any two of the three values, we can calculate the third value. We can determine a variety of useful information knowing our RSSI reading and one other parameter.

We will first need the E, or field strength values, of some nearby sample stations. We will use those values in our formula to calculate some antenna factors for various frequencies in the mediumwave band. They should prove relatively close in value. We will then average them to get an overall average antenna factor value, or AF.

Item #1, field strength E, for daytime reception out to about 200 miles of our chosen stations can easily be gotten from the V-Soft Zip Signal site. Accuracy is very good, and compares to within approximately 5% of the enhanced Norton signal strength formula I use in pattern calculation. Field strengths are published to your zip code origin, which is generally your post office latitude-longitude. Using some sample field strength values and the RSSI values from our receiver, we can calculate an approximate antenna factor for our radio.

Once we know the antenna factor, using simple addition we can calculate the field strength of any station we receive by adding the antenna factor dB right to the RSSI reading!



Note the value "A" in the pictured formula - Cable attenuation. We can ignore this in our formula as we have no feed line! We are measuring right at the antenna itself.

Before we get to our calculation examples, let me clear up one item of mis-represented terminology, the dBµV/m. In engineering parlance, field strength, or millivolts per meter (mV/m) is usually converted to dBµV/m and casually referred to as dBu (lower case "u"). It is NOT the same as the dBµ sticker (the RSSI value) on your DSP radio. "Engineer's dBu", the decibel representation of microvolts per meter, is RF field at the antenna and is short for dBµV/m. The radio's value "dBµ" is voltage output of the ferrite loop as compared to one microvolt, properly known as dBµV. Shame on Tecsun and others for printing dBµ on their radios. Inaccurate and very confusing.

ON TO THE CALCULATIONS AND EXAMPLES

The mediumwave E field at the receiver site (the antenna) is usually measured in millivolts per meter, mV/m. Though V-Soft will show the conversion of millivolts per meter to dBµV/m for you, you might want to be able to do it for yourself at some point.

If you'd like to figure it yourself, you can by using the following formula:

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

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

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

                              ...or back to microvolts per meter:

                              µV/m = 10 ^ (dBµV/m / 20)

Note: Log is the common logarithm, or base 10.

Let's try some calculation examples to get a baseline. We'll start at the lower end of the band using our Tecsun PL-880.


KTAR-620

Phoenix's daytime KTAR-620 is 129 miles east of me over fairly flat desert terrain. The station runs 5 KW daytime. Center tuned to KTAR on the Tecsun PL-880, the RSSI display shows a 35 dBµV signal off the ferrite loop. The V-Soft chart for my zip code shows the expected field strength of KTAR should be 0.83 mV/m (830 microvolts per meter), equivalent to 58.3 dBµV/m. We subtract our RSSI dB reading from the V-Soft dB value (58.3 - 35) = 23.3 to arrive at our antenna factor in dB. So our AF = 23.3 dB/m.

KBLU-560

Yuma, AZ daytime KBLU-560 is 69 miles south of me over rugged, mountainous desert terrain. The station runs 1 KW daytime. Center tuned to KBLU on the PL-880, the RSSI display shows a 35.5 dBµV signal off the ferrite loop. The V-Soft chart for my zip code shows the expected field strength of KBLU should be 1.28 mV/m (1280 microvolts per meter), equivalent to 62.1 dBµV/m. We subtract our RSSI dB reading from the V-Soft dB value (62.1 - 35.5) = 26.6 to arrive at our antenna factor in dB. So our AF = 26.6 dB/m.

Another example, but this time let's use a different frequency at mid-band.

KNTR-980

Daytime Lake Havasu, AZ KNTR-980 is 58 miles north of me over varied desert terrain. The station runs 1 KW daytime. Center tuned to KNTR on the PL-880, the RSSI display shows a 28 dBµV signal off the ferrite loop. The V-Soft chart for my zip code shows the expected field strength of KNTR should be 0.77 mV/m (770 microvolts per meter), equivalent to 57.7 dBµV/m. Our difference here between the V-Soft reading and the RSSI reading is 29.7 dB. So our AF = 29.7 dB/m.

Let's do one more example, this one a little farther up in the band.

KPXQ-1360

Phoenix's daytime KPXQ-1360 is 116 miles east of me over fairly flat desert terrain. The station runs 50 KW daytime. Center tuned to KPXQ on the PL-880, the RSSI display shows a 20 dBµV signal off the ferrite loop. The V-Soft chart for my zip code shows the expected field strength of KPXQ should be 0.33 mV/m (330 microvolts per meter), equivalent to 50.3 dBµV/m. Our difference here between the V-Soft reading and the RSSI reading is 30.3 dB. So our AF = 30.3 dB/m.

THE ANTENNA FACTOR

So we are seeing that the antenna factor for our ferrite loop in the PL-880 is generally in the upper 20s on average. The antenna factor will vary a little from the low end of the band to the high end. This is because our ferrite may be less sensitive at one end versus the other. Not unusual. Mine tends to run in the low 30s near the high end and the middle 20s at the low end, signifying that the sensitivity of my PL-880 is a little better at the low end of the band. It's exactly the reverse of what you might think. The lower the antenna factor's dB value is, the better is the ferrite's (or any antenna's) ability to convert the field to a voltage.

I have averaged these stations above and several others and have chosen an average antenna factor value of 27 dB to work with.

CHECKING SOME STRONG SKYWAVE

Now that we have an average antenna factor of 27 dB for the PL-880 let's find a strong station at night and see what kind of field strength it's putting into my location here in Arizona. KCBS-740 (50 KW) out of San Francisco, CA is a good choice, and puts in a tremendous signal here at night. Average RSSI readings on the PL-880 are in the 48 dBµV area when the signal is peaking.

Adding our antenna factor, 27 dB, to 48 dBµV, we get 75 dBµV/m. 75 dBµV/m is 5623 µV/m (microvolts per meter) or 5.623 mV/m (millivolts per meter). Now of course being skywave, this value will hardly be published as such in a field strength chart due to the extreme number of variables involved in skywave propagation. However, with our DSP radio we can read it's instantaneous value and calculate what its instantaneous field strength is.

Remembering the radio-locator signal strength scheme for daytime strengths:

  • 2.5 mV/m (68 dBuV/m, local)
  • 0.5 mV/m (54 dBuV/m, distant)
  • 0.15 mV/m (43.5 dBuV/m, fringe)

We can see KCBS-740 at 5.623 mV/m puts a whopping signal into southwestern Arizona, at urban levels at night, stronger than any daytime station due to our remote location.

CHECKING A WEAK ONE

Let's check the base reception level of our PL-880 - its ability to pick up the weakest signal it can. High daytime KMZQ-670 out of Las Vegas, NV (25 KW), 198 miles distant, is right at the noise level on my PL-880, running about 15-16 dBµV. Adding our antenna factor 27 dB to 16 dBµV, we get 43 dBµV/m. Converting 43 dBµV/m back to microvolts per meter we get 141 µV/m or 0.141 mV/m (millivolts per meter). This can be confirmed by radio-locator, as the radio-locator coverage map shows KMZQ's fringe (blue line, 0.15, or 40 dBµV/m) to be very close to my location.

So we see that our PL-880 has the ability to receive signals during the daytime out to radio-locator's fringe ring, or 0.15 mV/m (40 dBµV/m).

CHECKING OUR NOISE LEVEL

Generally in quiet locations, the mediumwave broadcast band's atmospheric noise level runs about 0.063 mV/m, or 36 dBµV/m. What will our PL-880's ferrite loop output be for a signal right at the noise? We can calculate that easily. 36 dBµV/m - 27 dB = 9 dBµV or 2.81 microvolts. This is also -97.9 dBm into a 50 ohm load. dBm is a figure generally used in defining sensitivity of receivers, meaning the decibel ratio compared to one milliwatt (m). In this case we are -97.9 dB less than one milliwatt! Remember, -107 dBm is equivalent to 1 microvolt signal strength at the antenna output, or 1 millionth of a volt. The lower the number in dBm (the more negative), the weaker the signal is. We see that the PL-880 hears down to about 0.15 mV/m, but not quite to the 36 dBµV/m atmospheric noise level of 0.063 mV/m.

CHECKING A DIFFERENT RADIO AND ANTENNA

I have an Eton Traveler 3 from which I've removed the ferrite loop and replaced it with an 18 inch box loop. The loop is wired directly to the radio's input. This means the DSP chip's RSSI value will be directly reading the voltage off the loop. We can determine it's antenna factor too.

For our test station let's use Yuma's daytime KBLU-560 signal again, 69 miles distant running 1 KW. Our RSSI display shows a 58 dBµV signal off the hardwired loop. The V-Soft chart (as before) shows the expected field strength of KBLU should be 1.28 mV/m (1280 microvolts per meter), equivalent to 62.1 dBµV/m. We subtract our RSSI dB reading from the V-Soft dB value (62.1 - 58) = 4.1 to arrive at our antenna factor in dB.

So the antenna factor for our 18 inch box loop is very low at 4.1 dB. Notice also that we have a 58 dBµV signal voltage being output as compared to the 35.5 dBµV signal voltage off the PL-880's ferrite, meaning much greater signal gain. Quite an improvement from the ferrite loop of the PL-880! A quick subtraction shows we have a 58 - 35.5 or 22.5 dB voltage gain. Converting the dBuV values to actual voltage, we have jumped our output from 59.5 microvolts to 794 microvolts, a 13.3 ratio increase by using our 18 inch passive loop!

WRAPPING IT UP

So there you have it. A new field strength measuring device awaits your testing! Be sure to remember to use the same units in your calculations. Don't mix millivolts per meter with microvolts per meter, or dB with actual voltage.

I hope I've provided for you some new and interesting things to try. Be sure to realize that the values we are calculating are ballpark values. They are not exact like might be read off a $15K dollar field strength device like the Potomac 4100. But even ballpark values can tell us many interesting things about our radio environment and the modern marvel DSP receiver.

Potomac 4100 - $15K


Friday, November 15, 2019

DSP Radio Chip Notes

A recent re-inspection of the Silicon Labs DSP radio chip datasheets left me with some new impressions of their quirks and capabilities. Additionally, a question was recently asked about observed differences in sensitivity between ultralight DSP portables. I thought I'd talk a bit about this and also some other general DSP chip notes related to chip radios.

SENSITIVITY

Consumer chip-based DSP radios are really quite simple in their design. Many if not nearly all of the portable radios we DXers use are employing the Silicon Labs Si4734/35 or Si4831/35 chips. The Si47xx is first generation and the Si48xx is the second generation or newer chip. Their basic functionality is the same.

Circuit-wise, in most consumer-grade radios the chip is generally wired right to the input coil, that is, it is connected directly to the two wires of the ferrite loop. Simplicity! Largely gone are the days of superheterodyne local oscillators and ferrite loops with touchy and complicated multiple windings which are difficult to align. The entire radio is right there on the chip.

The core-sensitivity of every "radio on a chip" is identical. Manufacturing defects or minor chip-to-chip manufacturing differences should be near nil. Connected directly to the ferrite loop, the sensitivity differences in radios therefore are defined by the length and efficiency of the ferrite loopsticks and also their shielding and positioning away from noisy circuitry.

SIGNAL STRENGTH

The dBµ signal strength display "19" on the front of this radio (RSSI reading, actually in dBµ/V) is reading the voltage off the ferrite loop as input to the chip. 19 dBµ represents 19 dB above one microvolt. Converted, it is 8.91 microvolts. So the dBµ signal strengths you are seeing are really a measure of antenna voltage and not differences in sensitivity of the chips, all other things being the same. Essentially you are seeing the sensitivity and efficiency of your ferrite loop, measured by the radio. How cool is that!

Another interesting fact to consider is the AM sensitivity of the 1st generation Si4734/35 chip and the 2nd Si4831/35 chip differ by 5 microvolts. Surprisingly the older Si4734/35 is the more sensitive - 25 µV vs. 30 µV (lower is better). But this difference (about 1.5 dB) will be hardly perceptible in reception. Still, a little improvement often makes the difference when signals are at the noise level.

The renowned CCRadio EP Pro uses the same 2nd generation Silicon Labs Si4831/35 chip we are discussing here. It achieves its nearly on-par sensitivity with the famed Panasonic RF-2200 because of its 200mm twin-coil, tuned ferrite loopstick. You can make a Tecsun PL-380 as sensitive as a Panasonic RF-2200 simply by removing the ferrite loopstick and substituting a 24 inch air core loop. A great trick except for the signal overload which cannot be handled adequately by the 380's DSP chip.

The second generation improvements in the Si4831/35 chips seem to be mostly added bells and whistles in control circuitry. However the sensitivity of the FM section of the newer Si48xx has been improved considerably, from 4 µV down to 2.2 µV (again, lower is better), amounting to nearly a 6 dB improvement.

It should be noticeable as it's almost a doubling of the signal sensitivity. Consequently if you are an FM Dxer, be on the lookout for newer DSP radios that use the second generation Si48xx chips.

ON CHANNEL?

Does your radio's sensitivity seem off? My PL-880 seemed so right from the start. An additional item to consider is channel centering. In other words, is the channel you are tuned to centered in the filter passband? One would assume that in a DSP-based radio the channel would always be centered. Not necessarily true. I bought a Tecsun PL-880 about a year ago. I was disappointed with it's sensitivity on mediumwave and found it was no better than my PL-380 or Sony SRF-59. I did the SSB centering tweak, noting that this was fairly close right out of the box. Still no improvement, but that effects SSB reception only. What to think? Did I get a bum unit?

Tecsun PL-880

The PL-880 has a wonderful fine tuning control available all the time - right under the main, or coarse, tuning control. It's a separate dial which allows tuning in finer 1 KHz steps. Now a year later, recently after tuning to a fairly weak mediumwave station, I happened to bump the fine tuning up 2 KHz and noticed something very unusual. The signal's audio got stronger and more bassy and the RSSI strength on the meter (dBµ) increased by +5 dB. The next day at mid-day I performed the same test on distant groundwave station KFI-640, Los Angeles, about 240 miles distant. KFI is one of my test stations when I test and compare radio sensitivities. I had only been able to get about 16 dbµ out of KFI at mid-day, with difficult reception just barely above noise level. Tuning up 2 KHz to 642, KFI now shows about 21-22 dBµ with clear audio and acceptable reception, well above the other two radios mentioned.

So check your channel centering in AM mode on these radios. Note that with some DSP radios this test might not be possible. Unfortunately what happens on some models is the RSSI reading will drop to zero since you are off-channel, making checking signal strength impossible. Check your radio to see.

OVERLOAD AND STATIC ZAPS

I hear talk all the time about connecting up modern portables to longwire antennas. Some portables even have a separate antenna jack for shortwave and even mediumwave. My advice: be careful. And be even more careful if you live in a dry climate like the desert where humidities are very low.

Many years back, I blew out two Sony ICF-2010s with attached longwire antennas. Understand, the '2010 was notoriously sensitive to external antennas even though it was set up for it. The overload, whether it be signal or static pulse, would zap the input FET transistor. It was replaceable and you could even get one at Radio Shack.

My Kaito KA-1103 was very sensitive to static discharge, though technically the original is not a DSP chip radio. The PL-880 is turning out to just as sensitive to static. It's common here in the desert at certain times of the year when it's extremely dry to get a static discharge off a door knob or other metal object, or radio, grounded or not. Recent static discharges to the PL-880 are resetting it just by picking it up while I'm slightly charged. No harm so far. The '1103 got to the point where it corrupted the ROM and wouldn't work anymore. And guess what you have when you connect your little radio up to a longwire? A giant atmospheric static discharge receptor fed right to the radio's input circuitry. You don't have to be in a thunderstorm with lightning to have a static pulse.

Tecsun PL-380

So on to the Sangean ATS-909X. About a month into owning the '909X the AGC started acting up. Sensitivity was way down as observed on the field strength meter. Reception then became intermittent and within minutes would eventually  fail altogether. At first, resetting the radio - but only by removing the batteries - corrected the problem. The problem would reoccur and I went through the same routine each time. In the end it became permanent and resetting the radio had no effect. The radio was dead. What had I been doing the week before all this started? I had been messing with a longwire antenna connected to the antenna port. Coincidence? Maybe, maybe not. As I have witnessed in the previous paragraph, static pulse can not only zap the front end of the radio, it can corrupt the radio's ROM operating system. Resetting the radio does not always fix this. I sent the '909X in to Sangean for repair and they reprogrammed the ROM. The radio has been fine ever since.

I've done a lot of experimenting with directly-connected air core loops, particularly with the PL-380 and Eton Traveler III. It is common to overload or even static-zap these radios in this way because of your direct connection to the input pin on the SiLabs DSP chip. In these cases the radio has so far always recovered. The symptoms are de-sensing of the radio to zero signal for perhaps ten minutes or so. Shut the radio off and let it recover if it will.

Again, be careful. Modern transistorized or chipped portables will not stand up to longwire antennas and static pulse like the old tube radios of yesteryear did. Ground the longwire temporarily at first  before connecting to the radio.

USING CHIPS IN DIFFERENT WAYS

Sangean ATS-909X
On rare occasion, a design engineer will use one of these chips in a different fashion and to greater advantage. Sangean was one of them. In what I consider one of the most highly underrated radios - the Sangean ATS-909X - engineers used the SiLabs DSP chip at the back end of the radio, in the I.F. section. This, to take advantage of the chip's superior DSP filtering in the I.F. stage, running the I.F. signal through the chip.

So, incorporating this into a traditional PLL-designed radio is a stroke of genius, combining the best of old front-end design with new technological filtering abilities at the I.F. stage. The result is a radio with premium selectivity.



WRAP UP

I am guilty as most, I continue to buy this DSP stuff hoping for a more sensitive radio. But the truth of the matter is that they are all basically the same in their electronics when they use the same chip, unless of course they use some kind of additional input or bandpass filtering ahead of the DSP chip or pre-amplification of the signal off the ferrite loop or are engineered into a different design like the Sangean ATS-909X. Few do. Otherwise the difference lies only in the base output off the ferrite loopstick, its length, antenna factor (efficiency), or positioning in relation to surrounding circuitry (a source of birdies and display noise).

To wrap up, go for the radios which have the longest ferrite loopstick. Until newer 3rd generation DSP chips come out, hopefully with greater sensitivity and lower noise floors, the only difference is in your ferrite or external antenna.

Next up: DECODING ANTENNA FACTOR IN FERRITE LOOPS

Silicon Labs Products page:

https://www.silabs.com/products/audio-and-radio/multi-band-radios

From the Silicon Labs site. Modern DSP chip usage in commercial and consumer radios:

Si4730    FM/AM Receiver
Si4731    FM/AM Receiver with RDS
Si4734    FM/AM/SW/LW Receiver
Si4735    FM/AM/SW/LW Receiver
Si4736    FM/AM/Weather Band Receiver
Si4737    FM/AM/Weather Band Receiver with RDS
Si4738    FM/Weather Band Receiver
Si4739    FM/Weather Band Receiver with RDS
Si4820    Mono FM/AM Receiver
Si4824    Mono FM/AM/SW Receiver
Si4825    Advanced Mono FM/AM/SW Receiver
Si4831    Stereo FM/AM Receiver
Si4835    Stereo FM/AM/SW Receiver
Si4836    Advanced Stereo FM/AM/SW Receiver
Si4822    Mono FM/AM Receiver
Si4826    Mono FM/AM/SW Receiver
Si4827    Advanced Mono FM/AM/SW Receiver
Si4840    Stereo FM/AM Receiver
Si4844    Stereo FM/AM/SW Receiver

Tuesday, November 5, 2019

Thoughts On All Digital AM

The FCC's recent NPRM docket 19-311 has been brought forth proposing rule changes authorizing AM stations to commence all-digital broadcasting on the mediumwave band. The outcome should be interesting and may institute a sea-change in the direction of AM radio. Currently approved stations may transmit a hybrid digital-analog combination or "IBOC" signal (In Band On Channel, by iBiquity). As of this writing, some 237 stations are authorized by the FCC. Roughly only 114 are actively transmitting a hybrid signal at all, with only approximately 32 transmitting hybrid at night under skywave conditions.

Notice of Proposed Rulemaking, 19-311 (PDF)

Sit back and think for a minute what AM DXing might be like in an all digital environment. YouTube has a few videos showing tuning of digital AM DX. Search for "DXing AM HD Radio". In the United States, one must only look to when TV broadcast went to all (or virtually all) digital mode in 2009 to see the effect.

I don't know if you have ever done any TV DXing, but back in the day analog TV DXing was relatively easy when signals were in. You could see if a signal was there or not amongst the "snow" on your screen. Digital broadcasts are different. A signal is there or it isn't, and when it's there it's there in full HD. The penalty that digital imposes over the older analog method is this: any reception at all requires a signal level above a certain threshold. Software controls that threshold. If the threshold is exceeded, you have a picture. If not exceeded you have nothing, not even evidence of something lurking in the noise.

"AM" radio digital reception, or HD Radio as it is known,  brings with it similar characteristics as digital TV reception. The signal will either be there or not, as the YouTube videos prove. At night with skywave prevailing, with a few or many stations sharing the same channel, I would expect signals to be popping in and out in perfect clarity.... if they break the threshold. On weaker channels, there may be nothing where before there was something detectable. This will certainly make DXing interesting. Threshold levels of receivers, set by mass market engineers, will dictate what is receivable.

So what about extreme mediumwave DX? Cross-continent DX may become extremely rare if not non-existent. Extremely weak signals may never break the threshold to be received. This may mean no more logging KFI-640 on the east coast, or WGY-810 on the west coast. And intercontinental DX, like trans-Atlantic (TA) or trans-Pacific (TP) will become virtually non-existent when those countries go to an all digital format. While single hop DX out to maybe 1000 miles or so might be possible on occasion, the extreme may never be again.

Note, however, that the TV DXing hobby continues to survive in the United States, despite digital. What's left are a few low power analog TV translator stations (channel 36 out of Kingman, AZ is one here is the southwest). These are mandated to convert to digital soon. Mexico still runs much analog TV. And there are people and groups still pursuing continental digital TV DX via E-layer skip and also through troposhperic ducting, predominantly near coastal areas.

More on TV and FM DXing can be found here at the Worldwide TV-FM DX Association.

Mediumwave broadcast band DXing will not stop just because of an eventual all-digital changeover. And any changeover will be years in the making unless the FCC suddenly mandates exclusive rights to digital and bans analog altogether. HD Radio hardware is available today, and has been predominately produced for the automotive market but more and more is being seen in home entertainment equipment. We will use different techniques in DXing. What will vanish, to a large degree, is that experience of pulling a weak signal up out of the noise and identifying it. To a guy like me raised on 1950s radio, it will be a disappointment. But new experiences await I suppose.

The trend to eliminate weak signal "annoyances" in radio reception is already being set in the last few years with the advent of DSP receivers using the SiLabs DSP chips, the "radio on a chip". Soft muting in these DSP chips eliminates weak signals at the noise level on purpose. Almost all modern consumer grade radios are now using this chip. In rare cases, the soft-mute function can be defeated. Analog is disappearing in many forms. Try to find a new, true analog-tuned radio on Amazon and you'll be surprised that there are only a slender few to choose from.

Now that we are some 10 years into all digital TV, it is notable that TV tuners in modern TVs have been dumbed down, desensitized, and capture threshold levels increased to where weak signal TV reception is becoming a thing of the past. This is evident with the TV DXing crowd who prefer older, more sensitive TV tuners made at the start of the digital conversion era, and covet sensitive analog to digital converter boxes made at the transition time (example: 2009, the Zenith DTT901 Digital TV Tuner Converter Box).

Tecsun has announced the availability of the new PL-990 and H-501 for early next year, two new multi-band portables. However the long term trend in radio is not to expand this line but to curtail it. With the near total demise of high power international shortwave broadcasting, fewer and fewer consumer radios with shortwave will be produced. Shortwave awaits the final nail in its coffin and the younger generations shows little interest because other technologies have supplanted the need.

Log 'em while you can. Interesting times are ahead.

Thursday, October 31, 2019

Canadian Mediumwave - Low Power 10-31-2019

Since I was in there messing with the Industry Canada database anyway, I decided to compile a list of OP or "operational" low power stations in the Canadian provinces. This is per the Industry Canada database and all accuracy is determined by them. Generally I have found that this database is highly accurate for facilities within Canada.

64 separate stations are represented. I've divided them into two groups - daytime operations and nighttime operations. Each facility operates both a daytime and nighttime service.

The unusual station call signs (like CBF-17, CBOF-4, etc.) are the way Industry Canada identifies newest changes, e.g., when a station changes operating parameters, etc.

Daytime

CallSign Frequency Power Location Towers
(D)CKML 530.000 30 Chalk River, ON 1
(D)CBKO 540.000 40 Coal Harbour, BC 1
(D)CBYW 540.000 40 Wells, BC 1
(D)CBKU 630.000 40 Sayward, BC 1
(D)CBOI 690.000 40 Ear Falls, ON 1
(D)CBES 690.000 40 Ignace, ON 1
(D)CBDM 690.000 40 Beaver Creek, YT 1
(D)CBF-17 710.000 40 Lac-Edouard, QC 1
(D)CBOM 710.000 40 Maniwaki, QC 1
(D)CBUN 740.000 40 Salmo, BC 1
(D)CBKJ 860.000 40 Gold River, BC 1
(D)CBTG 860.000 40 Gold Bridge, BC 1
(D)CBKM 860.000 40 Blue River, BC 1
(D)CBUG 860.000 40 Kaslo, BC 1
(D)CBKZ 860.000 40 Clearwater, BC 1
(D)CBUP 860.000 40 Merritt, BC 1
(D)CKSB-2 860.000 40 St-Lazare, MB 1
(D)CBUM 900.000 40 Nakusp, BC 1
(D)CBRK 900.000 40 Kimberley, BC 1
(D)CBKG 920.000 40 Granisle, BC 1
(D)CBWF 920.000 40 Mackenzie, BC 1
(D)CBDK 940.000 40 Teslin, YT 1
(D)CBKN 990.000 40 Shalalth, BC 1
(D)CBOF-1 990.000 40 Maniwaki, QC 1
(D)CBF-16 990.000 40 Clova, QC 1
(D)CBQJ 990.000 40 Ross River, YT 1
(D)CBQF 990.000 40 Carmacks, YT 1
(D)CBLW 1010.000 40 White River, ON 1
(D)CBON-6 1010.000 40 Blind River, ON 1
(D)CBUU 1070.000 40 Clinton, BC 1
(D)CBON-12 1090.000 40 Mattawa, ON 1
(D)CBSI-5 1100.000 40 Natashquan, QC 1
(D)CFQI 1110.000 20 Caledon East, ON 1
(D)CBSI-23 1130.000 40 Port-Menier, QC 1
(D)CBJ-2 1140.000 40 Chapais, QC 1
(D)CBF-4 1140.000 40 Matagami, QC 1
(D)CBXA 1150.000 40 Mica Dam, BC 1
(D)CBRH 1170.000 40 New Hazelton, BC 1
(D)CBAK 1210.000 40 Aklavik, NT 1
(D)CBPD-1 1230.000 5 Glacier Park, BC 1
(D)CBLE 1240.000 40 Beardmore, ON 1
(D)CBLO 1240.000 40 Mattawa, ON 1
(D)CBQG 1280.000 40 Wrigley, NT 1
(D)CJRU 1280.000 99 Toronto, ON 1
(D)CBPP-1 1280.000 20 Parc National De L I, PE 1
(D)CJBW 1330.000 50 Jans Bay, SK 1
(D)CJEV 1340.000 50 Elkford, BC 1
(D)CBLB 1340.000 40 Schreiber, ON 1
(D)CBKY 1350.000 40 Keremeos, BC 1
(D)CBRZ 1350.000 40 Bralorne, BC 1
(D)CBSI-14 1350.000 40 Aguanish, QC 1
(D)CBOF-4 1400.000 40 Rolphton, ON 1
(D)CBMD 1400.000 40 Chapais, QC 1
(D)CBKA 1450.000 40 Stewart, BC 1
(D)CHMO 1450.000 50 Moosonee, ON 1
(D)CBLF 1450.000 40 Foleyet, ON 1
(D)CKDR-3 1450.000 40 Hudson, ON 1
(D)CBPC-1 1490.000 5 Glacier Park, BC 1
(D)CFNC 1490.000 50 Cross Lake, MB 1
(D)CBPP 1490.000 20 Prince Edward Island, PE 1
(D)CFYI 1510.000 20 Caledon, ON 1
(D)CBSI-8 1550.000 40 La Romaine, QC 1
(D)CBPK 1580.000 50 Revelstoke, BC 1
(D)CHYW 1630.000 99 Ottawa, ON 1

Nighttime

CallSign Frequency Power Location Towers
(N)CKML 530.000 30 Chalk River, ON 1
(N)CBYW 540.000 40 Wells, BC 1
(N)CBKO 540.000 40 Coal Harbour, BC 1
(N)CBKU 630.000 40 Sayward, BC 1
(N)CBES 690.000 40 Ignace, ON 1
(N)CBOI 690.000 40 Ear Falls, ON 1
(N)CBDM 690.000 40 Beaver Creek, YT 1
(N)CBOM 710.000 40 Maniwaki, QC 1
(N)CBF-17 710.000 40 Lac-Edouard, QC 1
(N)CBUN 740.000 40 Salmo, BC 1
(N)CBUG 860.000 40 Kaslo, BC 1
(N)CBKJ 860.000 40 Gold River, BC 1
(N)CBTG 860.000 40 Gold Bridge, BC 1
(N)CBKM 860.000 40 Blue River, BC 1
(N)CBKZ 860.000 40 Clearwater, BC 1
(N)CBUP 860.000 40 Merritt, BC 1
(N)CKSB-2 860.000 40 St-Lazare, MB 1
(N)CBUM 900.000 40 Nakusp, BC 1
(N)CBRK 900.000 40 Kimberley, BC 1
(N)CBKG 920.000 40 Granisle, BC 1
(N)CBWF 920.000 40 Mackenzie, BC 1
(N)CBDK 940.000 40 Teslin, YT 1
(N)CBKN 990.000 40 Shalalth, BC 1
(N)CBF-16 990.000 40 Clova, QC 1
(N)CBOF-1 990.000 40 Maniwaki, QC 1
(N)CBQJ 990.000 40 Ross River, YT 1
(N)CBQF 990.000 40 Carmacks, YT 1
(N)CBLW 1010.000 40 White River, ON 1
(N)CBON-6 1010.000 40 Blind River, ON 1
(N)CBUU 1070.000 40 Clinton, BC 1
(N)CBON-12 1090.000 40 Mattawa, ON 1
(N)CBSI-5 1100.000 40 Natashquan, QC 1
(N)CFQI 1110.000 20 Caledon East, ON 1
(N)CBSI-23 1130.000 40 Port-Menier, QC 1
(N)CBF-4 1140.000 40 Matagami, QC 1
(N)CBJ-2 1140.000 40 Chapais, QC 1
(N)CBXA 1150.000 40 Mica Dam, BC 1
(N)CBRH 1170.000 40 New Hazelton, BC 1
(N)CBAK 1210.000 40 Aklavik, NT 1
(N)CBPD-1 1230.000 5 Glacier Park, BC 1
(N)CBLE 1240.000 40 Beardmore, ON 1
(N)CBLO 1240.000 40 Mattawa, ON 1
(N)CBQG 1280.000 40 Wrigley, NT 1
(N)CJRU 1280.000 99 Toronto, ON 1
(N)CBPP-1 1280.000 20 Parc National De L I, PE 1
(N)CJBW 1330.000 50 Jans Bay, SK 1
(N)CJEV 1340.000 50 Elkford, BC 1
(N)CBLB 1340.000 40 Schreiber, ON 1
(N)CBKY 1350.000 40 Keremeos, BC 1
(N)CBRZ 1350.000 40 Bralorne, BC 1
(N)CBSI-14 1350.000 40 Aguanish, QC 1
(N)CBOF-4 1400.000 40 Rolphton, ON 1
(N)CBMD 1400.000 40 Chapais, QC 1
(N)CBKA 1450.000 40 Stewart, BC 1
(N)CBLF 1450.000 40 Foleyet, ON 1
(N)CKDR-3 1450.000 40 Hudson, ON 1
(N)CHMO 1450.000 50 Moosonee, ON 1
(N)CBPC-1 1490.000 5 Glacier Park, BC 1
(N)CFNC 1490.000 50 Cross Lake, MB 1
(N)CBPP 1490.000 20 Prince Edward Island, PE 1
(N)CFYI 1510.000 20 Caledon, ON 1
(N)CBSI-8 1550.000 40 La Romaine, QC 1
(N)CBPK 1580.000 50 Revelstoke, BC 1
(N)CHYW 1630.000 99 Ottawa, ON 1