tag:blogger.com,1999:blog-42602004126085237522024-03-17T22:59:42.464-04:00RADIO-TIMETRAVELLERRADIO-TIMETRAVELLER is a blog about radio and radio DXing, antennas, opinions, reviews - basically all things concerning radio. My particular emphasis is mediumwave and mediumwave DXing. I hope to bring some interesting articles, ideas, and facts to these pages, not just dry reception reports.RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.comBlogger194125tag:blogger.com,1999:blog-4260200412608523752.post-73831419557831757822024-03-16T09:00:00.010-04:002024-03-16T09:34:35.257-04:002024 Solar Eclipse DXing<p>DXing the mediumwaves promises to be an exciting event on April 8 during the 2024 total solar eclipse.</p><p>I've been mulling over the DX possibilities a lot lately and have come to some conclusions. I think it boils down to three promising DX scenarios.</p><p>Scenario 1. For those who live within or very near the path of totality, I believe best chances of DX would be first to listen to your southwest, along the path where totality is approaching. Darkness will already have happened in that direction, and a certain amount of residual de-ionization of the ionosphere will still remain. After the point of totality passes your location, I would swing my attention to the northeast.</p><p>Scenario 2. For those living within about 800 km (or about 500 miles) of the path of totality I believe best chance would be a perpendicular path across the totality path to a point roughly equidistant on the other side. This puts the signal reflection point right at the center of the totality path, or the deepest point of darkness.</p><p>Scenario 3. For those living more than about 800 km from the path of totality I believe best chance would be along a line from your receiving site to a perpendicular intersection to the totality path. This should define the greatest shaded path.</p><p>I think scenarios #1 and #2 have the best possibility for DX. Incidentally, across the U.S. the totality path varies from about 170 km to about 200 km wide, or 105-125 miles.</p><p>Important to keep in mind - skywave signal strength analysis is based almost entirely on the condition of the ionosphere at the reflection point, not at the receiving site. For single hop propagation, normally the reflection point is at the halfway point to the station along the great circle route.</p><p>That 800 km distance from the totality center I wouldn't hold as gospel. I'm throwing that figure out as a point where scenario #2 may start to transition to scenario #3.</p><p>Timing is of the essence for DXing. The shadow velocity exceeds 1000 mph, increasing from 1587 miles per hour at Eagle Pass, Texas to 3176 mph at Houlton, Maine. You may have only minutes to DX.</p><p>I'll be in Rochester, NY at the time of totality, and we are right at dead center. I'll be scenario #1. My plan is to listen to my southwest initially, where totality is approaching. I'll be listening particularly for WLW-800 in Cincinatti, OH, WHAS-840 in Lexington, KY, and others along or near that path.</p><p>Scenario #2 possibly holds the most promise. Calculate your distance to the path center line and look for stations on a direct line across the totality path and at an equal distance on the opposite side of the path from you. One such scenario might be WSB-750, Atlanta to a reception point in northwestern Illinois, central Iowa, or southern Wisconsin or southern Minnesota. Many possibilities on cross-paths exist here. I feel best results would be with a signal path that crosses the path of totality closest to 90 degrees.</p><p>A question was raised about the possibility of DX from Spokane, Washington, an extreme distance from the path of totality. That particular scenario would be scenario #3, more than 800 km to the path of totality. Maximum obscurity should be when northeast Texas (let's say the Dallas area) is experiencing full totality, as the great circle line to the totality path intersects at approximately 90 degrees to the line at that point. This would be at about 1848 UTC. I would listen for any signals along a great circle path between Spokane to anywhere from the Dallas area and northward.</p><p>Obviously, Spokane to Dallas is an extremely long one hop path, at about 2450 km. At that distance, the reflection point is near Denver, which will have a solar obscuration of 65.1 percent at maximum.</p><p>A Dallas area reception would be next to impossible I would think, but there are many more stations along that great circle path one could try for. Closer stations will obviously move the reflection point closer and start to reduce the solar obscurity. I did a scan along that path and there are some 340 stations within 200 km either side of the line of the great circle path between Spokane and Dallas.</p><p>Check out these links.</p><p><a href="https://nationaleclipse.com/cities_partial.html">https://nationaleclipse.com/cities_partial.html</a><br /></p><p><a href="https://eclipse.gsfc.nasa.gov/SEpath/SEpath2001/SE2024Apr08Tpath.html">https://eclipse.gsfc.nasa.gov/SEpath/SEpath2001/SE2024Apr08Tpath.html</a><br /></p><p><a href="https://eclipse2024.org/eclipse_cities/statemap.html">https://eclipse2024.org/eclipse_cities/statemap.html</a><br /></p><p>Click image for full size.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhr0iJxOYmq2TJui9wodDxU7uE-gRzqwF4dkf8avp9mvQ8__8R4UFRTeJ4EckFbS7Q5B_pq4O4k5GYWrVXSLtvJVaDWVNcEfMuSKPCa0tnK8NRSAHRmMZkvqhAswsTzt1TJPBXvghDGlkhr17HFBjF-0c_8sXF_52zwxxaN7R5klKucX7KIcNQqTxEzmZZ-/s1348/Image3.jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" data-original-height="798" data-original-width="1348" height="378" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhr0iJxOYmq2TJui9wodDxU7uE-gRzqwF4dkf8avp9mvQ8__8R4UFRTeJ4EckFbS7Q5B_pq4O4k5GYWrVXSLtvJVaDWVNcEfMuSKPCa0tnK8NRSAHRmMZkvqhAswsTzt1TJPBXvghDGlkhr17HFBjF-0c_8sXF_52zwxxaN7R5klKucX7KIcNQqTxEzmZZ-/w640-h378/Image3.jpg" width="640" /></a></div><br /><p><br /></p>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com0tag:blogger.com,1999:blog-4260200412608523752.post-48918238301760156072024-01-14T15:27:00.005-05:002024-01-14T15:28:28.109-05:00C.Crane Twin Coil Ferrite Signal Booster DISCONTINUED!<p>It's always been in my head to try an actual C.Crane Twin Coil Ferrite Signal Booster. I've used tuned Q-stick devices before with a lot of success. They have sharp nulls and lots of inductive gain. The Crane unit promised more of the same with its 8-inch twin coil ferrite rod.</p><p><a href="https://ccrane.com/twin-coil-ferrite-am-antenna-signal-booster">https://ccrane.com/twin-coil-ferrite-am-antenna-signal-booster</a><br /></p><p>Checking the Crane website the other day, I was shocked to find that they have discontinued it. Now, if I want to give it a try, I'll have to find one elsewhere - maybe eBay. I see there are a few of them out there yet. I'd advise you to pick up one of these fabulous goodies before they are gone forever.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwIxhi8sL2asiMlMQCsxODqqUX4zLCLzXX4L1cuJKSLEXDbrDrnWvSWv8YOs-P8g2Z7bqKZrMjnGvEC7o0jzcZIpo-xsWO4iCXvZgDsb2Rvuqv2c5NfRutipTKmIvGjY3QXqBqOU_2ew7FKOp6pVugxlYRkYUbHfwZ3YoFHvsfPyFDaR_AWuxGafarqbMo/s575/twin_coil2.jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" data-original-height="244" data-original-width="575" height="272" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwIxhi8sL2asiMlMQCsxODqqUX4zLCLzXX4L1cuJKSLEXDbrDrnWvSWv8YOs-P8g2Z7bqKZrMjnGvEC7o0jzcZIpo-xsWO4iCXvZgDsb2Rvuqv2c5NfRutipTKmIvGjY3QXqBqOU_2ew7FKOp6pVugxlYRkYUbHfwZ3YoFHvsfPyFDaR_AWuxGafarqbMo/w640-h272/twin_coil2.jpg" width="640" /></a></div><br /><p><br /></p>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com2tag:blogger.com,1999:blog-4260200412608523752.post-35510830922253852892024-01-10T13:58:00.004-05:002024-01-10T13:59:59.866-05:00U.S. Broadcast Station Counts 1922-2022<p>100 years of AM broadcast in the U.S.</p><p>Shown below on the graph are the counts of licensed stations in the FCC's AM broadcast service for the years 1922-2022. You will see a steady rise in counts from 1922 to 1990.</p><p>I remember listening as a kid in Philadelphia in the very early 1960s. The band was literally alive with stations every night from as far away as St. Louis (KMOX), San Antonio (WOAI), New Orleans (WWL), Minneapolis (WCCO), and many others. Even the Mexican border blasters with the likes of Wolfman Jack were a normal catch every night.</p><p>We are in slow decline over the past thirty years and gaining more downward speed in the last ten. When will it end? What decade was the heyday of AM broadcasting? You decide.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgIRZNNruT_Xjb_lIQYYJJcY2pJ_2kj26uAlg5s_CzODN6bW1pup2QYJPzgemu4nzWw00gh50fkcUnZRgCV7-oeqJ54HxB5FPsFOe-lLSQ6O85LIgP3GhkCsj7w8yPFLBHdasl-17EkDZi8ypTckEVS1JT-DU_fmCh29w1-bVq190yqIIKetX1GS5PrLEOT/s562/station_counts_1922-2022.png" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" data-original-height="527" data-original-width="562" height="600" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgIRZNNruT_Xjb_lIQYYJJcY2pJ_2kj26uAlg5s_CzODN6bW1pup2QYJPzgemu4nzWw00gh50fkcUnZRgCV7-oeqJ54HxB5FPsFOe-lLSQ6O85LIgP3GhkCsj7w8yPFLBHdasl-17EkDZi8ypTckEVS1JT-DU_fmCh29w1-bVq190yqIIKetX1GS5PrLEOT/w640-h600/station_counts_1922-2022.png" width="640" /></a></div><br /><p><br /></p>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com0tag:blogger.com,1999:blog-4260200412608523752.post-4078999324419968452023-11-24T04:07:00.002-05:002023-11-24T04:07:28.856-05:00Mediumwave Skywave Prediction #6 - Wrapping Things Up<div>Let's close up by defining a few of the terms used in the formulas from the last post, and finish by talking a bit about diurnal and seasonal effects.</div><div><br /></div><b>WHAT IS POLARIZATION COUPLING LOSS?</b><br /><br />Polarization coupling loss, sometimes depicted as Lp, is the fraction of incident power lost on entry into the ionosphere. Further polarization coupling loss occurs when the wave which emerges from the ionosphere induces a voltage in the receiving antenna. Polarization coupling loss depends to some extent on frequency and angle of incidence at the ionosphere. Polarization coupling losses are low in higher latitudes because the Earth's magnetic field is almost vertical. At the magnetic equator, however, the Earth's field is horizontal and polarization coupling losses on east-west paths are large.<br /><br />Polarization coupling loss at MF is an important factor in skywave propagation. It arises because the Earth's natural gyromagnetic frequency lies within the frequency band being considered. The gyromagnetic frequency of the Earth's ionosphere varies between 800 kHz in the equatorial regions and 1600 kHz near the magnetic poles. When a linearly polarized mediumwave frequency radio wave enters the ionosphere, it gets split into two waves known as ordinary and extraordinary. At the gyromagnetic frequency the extraordinary wave is so greatly attenuated that it makes a negligible contribution to the received signal. As a consequence, the extraordinary wave can be disregarded within the mediumwave band. The propagation is therefore by the ordinary wave.<br /><br />To explain further, conventional antennas at mediumwave radiate vertically-polarized waves. At MF, the wave which is accepted by the ionosphere and which will propagate back to Earth usually differs in polarization somewhat - hence the ionosphere may not be excited efficiently by the incident wave. We have decreased coupling efficiency, or polarization coupling loss. The wave which subsequently emerges from the ionosphere is in general elliptically-polarized and in-turn may not excite the receiving antenna efficiently because antennas near the ground are most sensitive to vertical polarization, resulting in additional loss.<br /><br /><b>WHAT IS SEA GAIN?</b><br /><br />For long distance paths (1000 to 6000 km or greater), when the path is over the sea and at least one end of the link is located on or near the sea coast, the phenomenon of sea gain can add from 3 to 10 dB to the predicted field strength. <div><br /></div><div>Gains peak at the usual single, double, and triple hop distances of 2000 km (8 dB), 4000 km (10 dB), and 6000 km (10 dB). Only about 3 dB is gained at the 1000 km distance. A dip in gain (to about 5 dB) occurs at about the 2500 and 5000 km distances.</div><div><br /></div><div>A knowledge of the land-sea boundary information is necessary to assess the sea gain phenomena. Generally, in the skywave calculation, the sea gain correction is normally set to 0 dB without this knowledge. To take any advantage of sea gain, one of the terminals (transmitter or receiver) must be within about 10 km from the sea coast. Even at 10 km inland, the penalty is about -4 dB. At 4 km, about -2 dB. At 3 km, only about a -1 dB penalty.<br /><br /><b>SOLAR CYCLE LOSSES</b><br /><br />Solar Cycle 25 is well on its way now, having started its general upward trend in sunspot count by late 2020. The daily sunspot count for August 30, 2023, for example, was 104.<br /><br />Do sunspots effect nighttime skywave propagation at the medium waves? Yes they do, at a small but noticeable level. Here are the details.<br /><br />Concerning medium wave, sunspots and the increasing solar flux are relevant to skywave field strength and are accounted for in most modern (nighttime) skywave prediction methods. In general, mediumwave skywave field strength is slightly better during low or zero sunspot periods, at the bottom of the solar cycle. The calculation of the additional path loss in dB is dependent on location.<br /><br />Greater consideration is given to paths within North America and Europe (nearer to the north geomagnetic pole), and Australia (nearer to the south geomagnetic pole). The North American loss factor is 4 times that of Europe and Australia, and rises for all as we get to the higher latitudes. Longer paths, those between North America and Europe are usually interpolated.<br /><br />The ITU skywave prediction method is one such method which incorporates these added loss factors due to sunspots and solar flux. Figures below have been extracted from that prediction method.<br /><br />Below are increased single hop skywave loss factors in dB as the sunspot count goes up.<br /><br />Paths within North America:<br /><br /><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px; text-align: left;">Sunspot count = 0 a net added loss of zero<br />Sunspot count = 7 an additional loss of 0.28 dB<br />Sunspot count = 25 an additional loss of 1 dB<br />Sunspot count = 50 an additional loss of 2 dB<br />Sunspot count = 100 an additional loss of 4 dB</blockquote><br />Paths within Europe:<br /><br /><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px; text-align: left;">Sunspot count = 0 a net added loss of zero<br />Sunspot count = 7 an additional loss of 0.07 dB<br />Sunspot count = 25 an additional loss of 0.25 dB<br />Sunspot count = 50 an additional loss of 0.5 dB<br />Sunspot count = 100 an additional loss of 1 dB</blockquote><br />Paths between North America and Europe:<br /><br /><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px; text-align: left;">Sunspot count = 0 a net added loss of zero<br />Sunspot count = 7 an additional loss of 0.175 dB<br />Sunspot count = 25 an additional loss of 0.625 dB<br />Sunspot count = 50 an additional loss of 1.25 dB<br />Sunspot count = 100 an additional loss of 2.5 dB</blockquote><br />Admittedly, these extra losses are small but important enough that they are factored in for skywave calculations. Be aware that 3 or 4 dB can make a difference logging a station or not. A single S-unit is 6 dB.<div><br /><div><b>DIURNAL EFFECTS</b><br /><br />The final determination which really completes our skywave field strength calculation must include three more tweaks:<br /><br /><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px; text-align: left;">1. Diurnal hourly losses/gains<br />2. Sunrise and sunset enhancements<br />3. Seasonally-driven losses/gains</blockquote><div><br /></div><div>The D-layer of the ionosphere is characterized as having a strong dependence on frequency, but this is present only during the daytime. The E-layer is the dominant contributor to LF and MF propagation at night and is only mildly dependent on frequency, so the effects of frequency of this layer can be neglected for most practical purposes.</div><div><br /></div><div>Although daytime ionospheric propagation is relatively unimportant, it cannot be entirely disregarded at the upper end of the band, since ionospheric attenuation decreases with the square of the frequency. Nor can it be entirely disregarded at the lower end of the band, where partial reflection from the lower edge of the D region may occur, especially in winter at temperate latitudes.</div><div><br /></div><div>The critical frequency of the normal E layer is about 1500 kHz at sunset, but it then falls rapidly as a result of electron-ion recombination and will assume a value of about 500 kHz late at night. Skywaves may be reflected from the E layer, or they may penetrate the E layer and be reflected from the F layer, depending on the frequency, path length, and time of night. Simultaneous reflection by both layers is also possible in some circumstances. </div><div><br /></div>Upper MW band diurnal (or daily) morning enhancement can show effect as late as 3 hours after sunrise. The start of the pre-sunset afternoon enhancement is delayed a little to about 2 hours before sunset, gradually building to sunset. The lower part of the band shows little of this effect, morning or night.</div><div><br /></div><div>The diurnal enhancement described in the last paragraph is not to be confused with the short sunrise and sunset enhancements on extreme DX due to what is called "greyline effect", the signal traveling along, or partly along, the sunrise/sunset terminator.</div><div><br />Skywave propagation does indeed exist during the daytime hours, and its strength varies greatly, seasonally.<br /><br />Daytime, noon-hour skywave is generally pegged at approximately 30 dB lower than the nighttime field-strength prediction, and this will vary considerably seasonally. An ionospheric transition period occurs immediately surrounding sunset and lasts till approximately four hours after sunset, and another occurs during the period from 2 hours before sunrise until sunrise where the field strength goes through this 30 dB change with a very steep slope. The shapes of the curves are not symmetrical for the transition from day-to-night and night-to-day.<br /><br /><b>WRAP UP</b></div><div><br /></div><div>In this series I have attempted to present to you first a little history skywave propagation analysis, who developed the formulas and how they are geographically dependent, and the formulas themselves. I hope it has brought some perspective to the process and you have enjoyed it.<br /><div><br /></div></div></div></div>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com0tag:blogger.com,1999:blog-4260200412608523752.post-15309113333404324742023-09-11T10:16:00.187-04:002023-09-11T13:26:25.364-04:00Mediumwave Skywave Prediction #5 - Dissecting The FormulasWe'll get to the actual skywave prediction formulas shortly, but first let's talk about how to calculate the geomagnetic midpoint of our signal path. To get this, we'll need the latitude and longitude of both the transmitter and receiver sites. We'll also need the latitude and longitude of geomagnetic north, which moves by small increments each year. A nice chart can be found at:<div><br /></div><div><a href="https://wdc.kugi.kyoto-u.ac.jp/poles/polesexp.html">https://wdc.kugi.kyoto-u.ac.jp/poles/polesexp.html</a><br /><br />The following geomagnetic north pole coordinates are accurate for 2023:<br /><br /></div> dipoleN = 80.8° latitude (actual)<br /><div style="text-align: left;"> dipoleW = 72.7° longitude (actual) -use a positive number in the final mid-point formula</div><div><br />Note: dipoleN and dipoleW are the geomagnetic north pole, NOT the magnetic north pole. There is a difference. To reiterate from the previous post, '<i>geomagnetic poles (dipole poles) are the intersections of the Earth's surface and the axis of a bar magnet hypothetically placed at the center the Earth by which we approximate the geomagnetic field. They differ greatly from the magnetic poles, which are the points at which magnetic needles become vertical. The magnetic poles are what has been "wandering", a subject in the news lately, but they drag the geomagnetic poles with them too, albeit at a lesser rate.</i>'<br /><br />First we'll calculate the actual geographic mid-point latitude and longitude between transmitter and receiver. The Movable-Type scripts website has our formula to do that:</div><div><br /></div><div><a href="https://www.movable-type.co.uk/scripts/latlong.html">https://www.movable-type.co.uk/scripts/latlong.html</a></div><div><br /></div><div>Many websites have geographic mid-point calculators as well. Those familiar with Javascript can use the formula below or convert it to a different language if you wish to do the calculation yourself.</div><div><br /></div><div><span style="font-family: courier;">lat1 = transmitter latitude in degrees</span></div><div><span style="font-family: courier;">lon1 = transmitter longitude in degrees</span></div><div><div><span style="font-family: courier;">lat2 = receiver latitude in degrees</span></div><div><span style="font-family: courier;">lon2 = receiver longitude in degrees</span></div></div><div><span style="font-family: courier;"><br /></span></div><div><div><span style="font-family: courier;">double dLon = Math.toRadians(lon2 - lon1);</span></div><div><span style="font-family: courier;"><br /></span></div><div><span style="font-family: courier;"> //convert to radians</span></div><div><span style="font-family: courier;"> lat1 = Math.toRadians(lat1);</span></div><div><span style="font-family: courier;"> lat2 = Math.toRadians(lat2);</span></div><div><span style="font-family: courier;"> lon1 = Math.toRadians(lon1);</span></div><div><span style="font-family: courier;"><br /></span></div><div><span style="font-family: courier;"> double Bx = Math.cos(lat2) * Math.cos(dLon);</span></div><div><span style="font-family: courier;"> double By = Math.cos(lat2) * Math.sin(dLon);</span></div><div><span style="font-family: courier;"> double lat3 = Math.atan2(Math.sin(lat1) + Math.sin(lat2), Math.sqrt((Math.cos(lat1) + Bx) * (Math.cos(lat1) + Bx) + By * By));</span></div><div><span style="font-family: courier;"> double lon3 = lon1 + Math.atan2(By, Math.cos(lat1) + Bx);</span></div><div><span style="font-family: courier;"><br /></span></div><div><span style="font-family: courier;"> //answer in degrees</span></div><div><span style="font-family: courier;"> mid_lat = Math.toDegrees(lat3);</span></div></div><div><span style="font-family: courier;"> mid_lon = Math.toDegrees(lon3);</span></div><div><br /></div><div>mid_lat and mid_lon is the actual geographic mid-point of our path.</div><div><br /></div><div>Now, we'll use a separate formula to translate the actual mid-point latitude-longitude to geomagnetic latitude:<br /><br /></div><div style="text-align: left;"><span style="font-family: courier;"> ThetaM(radians) = </span></div><div style="text-align: left;"><span style="font-family: courier;"> Asin(Sin(mid_lat) * Sin(dipoleN) + Cos(mid_lat) * Cos(dipoleN) * Cos(dipoleW + mid_lon))</span></div><div><br />ThetaM will be in radians and must be converted to degrees. To do so:<br /></div><div><br /></div><div><span style="font-family: courier;"> ThetaM(degrees) = (ThetaM(radians) * 180) / Pi</span></div><div><br /></div><div>ThetaM is the geomagnetic latitude in degrees.</div><div><br /></div><div>Let's dive right into the skywave prediction formulas. We know slant distance, geomagnetic latitude of the path mid-point, and we have everything we need to calculate Kr, the aggregated ionospheric losses. Take note that the skywave prediction normally is the prediction for the local midnight hour, equidistant between sunset and sunrise, commonly referred to as SS+6, or sunset + 6 hours.<br /><br /><b>WANG FORMULA DETAILS</b><br /><br />The Wang method is the only method which offers good to excellent results for short and long paths alike at all frequencies in the LF/MF bands, at all latitudes, and in all regions. It has been demonstrated that the Wang method is the only method that can be considered a true worldwide method.<br /><br />The Wang expression for field strength is:</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJ7f1EnnQSECI2rBIGB29SQrUx_ief7V-OHAF5YAdMu8x66A-GfZs89x9dM9G6-6_9I2wsrHXqs3Ix83hsD2gsCEe5nHOpKXk0w3Msu8SEXGTBhfJ7TUsWyhrokgkVc0rIpn0_uE66_ApxQxrAaf60NVTnnYN9Wfu9p0gF09HfaLEfsuzpL79ywBb4Hh7-/s471/wang_formula.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="32" data-original-width="471" height="22" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJ7f1EnnQSECI2rBIGB29SQrUx_ief7V-OHAF5YAdMu8x66A-GfZs89x9dM9G6-6_9I2wsrHXqs3Ix83hsD2gsCEe5nHOpKXk0w3Msu8SEXGTBhfJ7TUsWyhrokgkVc0rIpn0_uE66_ApxQxrAaf60NVTnnYN9Wfu9p0gF09HfaLEfsuzpL79ywBb4Hh7-/w320-h22/wang_formula.jpg" width="320" /></a></div><div><br />Note: FS(dBu), is also known as dBµV/m.<br /><br />Where: FS(dBu) is the field strength in dBµV/m, V is the transmitter cymomotive force above the reference 300 mV in dB (better known as our effective radiated power (ERP) referenced to 1 KW in the direction of interest). ThetaM is the mid-point transmitter and receiver geomagnetic latitude, Dslant is the slant distance in km. Kr, or generalized ionospheric losses, are described below.<br /><br />In the Wang method, the 107 (dB) factor is used for most of the world. New Zealand and Australia use 110 dB, giving that part of the world a 3 dB field strength improvement (half an S-unit).<br /><br />To convert FS(dBu) back to millivolts per meter: mV/m = 10 ^ (FS(dBu) / 20) / 1000<br /><br />The generalized ionospheric losses are found in Wang's Kr factor. Both Wang and the FCC method calculate Kr in this manner:</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEikKT15qFkOQYpfDk4Q2-tjJDjfwcIpJq-oErnUk9mrBs1GWC4-uZrhY_m3N0Aze3du0azumsRYN98WIpIlnAwsmL1G-GQChskzAQa5M8u2m7rNKeY1JNNYEp_Nlm6u2vZwwXfy6g6Qu5s0Z7PANNTBTs3b_94dvRjC_FbqugBNG4NX5bfI7a8Svh9zAz5F/s559/wang-fcc_kr.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="31" data-original-width="559" height="22" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEikKT15qFkOQYpfDk4Q2-tjJDjfwcIpJq-oErnUk9mrBs1GWC4-uZrhY_m3N0Aze3du0azumsRYN98WIpIlnAwsmL1G-GQChskzAQa5M8u2m7rNKeY1JNNYEp_Nlm6u2vZwwXfy6g6Qu5s0Z7PANNTBTs3b_94dvRjC_FbqugBNG4NX5bfI7a8Svh9zAz5F/w400-h22/wang-fcc_kr.jpg" width="400" /></a></div><div><br /></div><div>Kr is the loss factor in dB, to include ionospheric absorption, focusing and terminal losses, losses between hops, geomagnetic latitude influence, and basic polarization coupling loss.<br /><br />Where: ThetaM is the geomagnetic latitude defined previously. Dslant, the slant distance, will modify Kr accordingly.<br /><br />Wang recommends that the geomagnetic mid-point latitude, ThetaM, be between -60 (south) and +60 degrees (north). When compared to the ITU expression, Wang's expression is symmetrical about zero degrees latitude and is not dependent on frequency.<br /><br />Let's do a Kr loss example for a 1500 km slant path and see what our ionospheric losses are.<br /><br />Here are the results for a single hop, 1500 kilometer (932 miles) slant distance for various mid-point locations. Using this Wang formula, I've prepared a chart showing the additional losses, in dB, caused by geomagnetic latitude influence.<br /><br /></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px; text-align: left;"><div style="text-align: left;"><span style="font-family: courier;">Basic Loss Deviation Geo-Lat Mid-Point (actual location of)</span></div><div style="text-align: left;"><span style="font-family: courier;">---------- ----------- ------- ------------------------------</span></div><div style="text-align: left;"><span style="font-family: courier;"> 7.854 dB 0 9.19 0°N, over the equator</span></div><div style="text-align: left;"><span style="font-family: courier;"> 8.347 dB +0.493dB 18.15 10°N, over Venezuela</span></div><div style="text-align: left;"><span style="font-family: courier;">10.637 dB +2.783dB 34.86 25°N, over south Florida</span></div><div style="text-align: left;"><span style="font-family: courier;">11.778 dB +3.924dB 39.37 30°N, over north Florida</span></div><div style="text-align: left;"><span style="font-family: courier;">14.553 dB +6.669dB 46.76 38°N, over Richmond VA</span></div><div style="text-align: left;"><span style="font-family: courier;">17.889 dB +10.035dB 52.36 43°N, over Rochester NY</span></div><div style="text-align: left;"><span style="font-family: courier;">18.767 dB +10.913dB 53.50 45°N, over Minneapolis MN</span></div><div style="text-align: left;"><span style="font-family: courier;">21.233 dB +13.379dB 56.21 48°N, over Grand Forks ND</span></div></blockquote><div style="text-align: left;"><br /></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div style="text-align: left;"><span style="font-size: x-small;">Basic Loss = the basic loss on this 1500 km path. The first entry has its mid-point (reflection point) over the equator.</span></div></blockquote><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div style="text-align: left;"><span style="font-size: x-small;">Deviation = additional loss incurred as latitudes increase using the basic equator loss as the base.</span></div></blockquote><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div style="text-align: left;"><span style="font-size: x-small;">Geo-Lat = the adjusted geomagnetic latitude of the reflection mid-point.</span></div></blockquote><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div style="text-align: left;"><span style="font-size: x-small;">Mid-Point = the actual geographic location of the reflection midpoint.</span></div></blockquote><div style="text-align: left;"><br />As you can see, we have lost over 13 dB in field strength when the reflection point is at 48° actual latitude!<br /><br />Here is an example of how geomagnetic positioning of the signal path affects the final field strength result. Reception of KFAB (1110 kHz), Omaha, Nebraska (41.23°N, 96.0°W) here in Rochester, NY, places the mid-point of our ionospheric reflection at a geomagnetic latitude of 51.355 degrees. The slant distance is 1548 km. An overall Kr loss of 17.45 dB gives an additional geomagnetic position penalty of some extra 9.596 dB over tropical paths!<br /><br />Now, let's calculate an expected skywave field strength value for 50 KW KFAB-1110 here in Rochester, NY. From above, we already know our slant distance is 1548 km. Our Kr loss factor from the example above is 17.45 dB.<br /><br /></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div style="text-align: left;"><b>FS(dBu) = V(-18.739) + 107 - 20 * Log10(1548) - 17.45</b></div></blockquote><div style="text-align: left;"><br /></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div style="text-align: left;"><b>FS(dBu) = 7.01</b></div></blockquote><div style="text-align: left;"><br />Converting to millivolts per meter:<br /><br /></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div style="text-align: left;"><b>mV/m = 10 ^ (FS(dBu) / 20) / 1000 ...convert dBu back to mV/m, or:</b></div></blockquote><div style="text-align: left;"><br /></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div style="text-align: left;"><b>.00224 = 10 ^ (7.01 / 20) / 1000</b></div></blockquote><div style="text-align: left;"><br />.00224 mV/m is a weak signal indeed.<br /><br />Why such a weak signal from a 50 KW powerhouse station at only ~1500 km? We are placed perfectly in KFAB's deep cardioid pattern notch at 76 degrees azimuth and a 4 degree takeoff angle. Facing us at those angles is a theoretical and nearly-microscopic 12.72 watts ERP. This is a primary lesson we learn from tower array pattern analysis, both skywave and groundwave. One will naturally think, "Well, it's a 50 KW station, and only a mere 960 miles distant. I should be getting a pretty good signal". Not necessarily so. If you are in a deep notch of a pattern, you may only be "seeing" a few watts facing you.</div><div style="text-align: left;"><br /></div><div style="text-align: left;">Take a look at the graphic below. You will see the deep cardioid notch of KFAB's nighttime pattern. Stations to the east suffer a great signal loss.<br /><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigz8FP7C2ovgG51pNm77IdUWQYUPxH21wcli-OpLOJWhturTdCyp4WDi3QIOA057BJaCKSxNy2I7wY-8WjiTDyJYPS_PLxy-G6DEf1Q75C_1VZEkX1xJP5vcvMR6IlpK0NRT6xob03ACoNLIZY7XKKb6UOYmhCpSHdcmj99JMOQJxXMM0Pc_n3zOK2dw-e/s1152/KFAB-1110_night_pattern.png" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="738" data-original-width="1152" height="256" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigz8FP7C2ovgG51pNm77IdUWQYUPxH21wcli-OpLOJWhturTdCyp4WDi3QIOA057BJaCKSxNy2I7wY-8WjiTDyJYPS_PLxy-G6DEf1Q75C_1VZEkX1xJP5vcvMR6IlpK0NRT6xob03ACoNLIZY7XKKb6UOYmhCpSHdcmj99JMOQJxXMM0Pc_n3zOK2dw-e/w400-h256/KFAB-1110_night_pattern.png" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">KFAB Nighttime Pattern. Click for larger image.</td></tr></tbody></table><br /><div style="text-align: left;">Where did the V(-18.739) figure come from, you ask? That is KFAB's facing 12.72 watts aimed at us, referenced to 1 KW, in dBW. It is 18.739 dB down from 1 KW. How did we get this and the 12.72 watts figure? The FCC has some rather serious formulas which will calculate power and mV/m levels delivered at any azimuth and elevation angle for any tower array. The FCC website for the station also provides a basic chart for each compass degree around the tower array, listing mV/m levels. This is the easiest to use, although it is calculated for 0 degrees takeoff elevation.</div><div style="text-align: left;"><br /><b>FCC FORMULA DETAILS</b><br /><br />The FCC method has close resemblance to the Wang method. The FCC expression for field strength is:<br /><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhbPDnX_oL4fpVJM9f3YdI-2dGIlwvMysHFCOumVBSD9bCVrWXZpl2d-ZyfXIhuj-b5VX2KhawmAYbBzxLLRqU4LuVO4e288wnFtDh6t6F2oL24lcr2vcIVKxMQhHSShRHskBupkZjj2Fo-18E1WM6HsF7L_IU4SP4kO-fZi_kZ8s0OF38QwR3EP6XxUuHU/s431/fcc_formula.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="32" data-original-width="431" height="24" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhbPDnX_oL4fpVJM9f3YdI-2dGIlwvMysHFCOumVBSD9bCVrWXZpl2d-ZyfXIhuj-b5VX2KhawmAYbBzxLLRqU4LuVO4e288wnFtDh6t6F2oL24lcr2vcIVKxMQhHSShRHskBupkZjj2Fo-18E1WM6HsF7L_IU4SP4kO-fZi_kZ8s0OF38QwR3EP6XxUuHU/w320-h24/fcc_formula.jpg" width="320" /></a></div><div style="text-align: left;"><br />Note: FS(dBu), is also known as dBµV/m (normalized to 100 mV/m, in dBµV/m per 100 mV/m).<br /><br />Where: FS(dBu) is the field strength in dBµV/m, ThetaM is the mid-point transmitter and receiver geomagnetic latitude, Dslant is the slant distance in km. Kr, or generalized ionospheric losses, are described below.<br /><br />The FCC formula would appear to not include any system gain, referred previously as "transmitter cymomotive force above the reference 300 mV in dB". The field strength predicted is normalized to 100 mV/m (in dBµV/m per 100 mV/m). We must convert this back to the actual mV/m value by multiplying by the number of 100 mV/m "portions" we have in the total mV/m measurement at 1 km. The total mV/m measurement is calculated and published by the FCC for each compass degree. This figure also contains our tower array gain - our effective radiated power (ERP) referenced to 1 KW from a quarterwave monopole.</div><div style="text-align: left;"><br />Converting to millivolts per meter, again:</div><div style="text-align: left;"><br /></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div style="text-align: left;"><b>mV100 = 10 ^ (FS(dBu) / 20) / 1000 ...convert dBu back to mV/m</b></div></blockquote><div style="text-align: left;"><br /></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div style="text-align: left;"><b>mV/m = mV100 * (measured_mVm@1km / 100) ...corrected to actual mV/m</b> </div></blockquote><div style="text-align: left;"><br /></div><div style="text-align: left;">The FCC formula uses Wang's identical Kr factor. The generalized ionospheric losses are again found in it:<br /><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEikKT15qFkOQYpfDk4Q2-tjJDjfwcIpJq-oErnUk9mrBs1GWC4-uZrhY_m3N0Aze3du0azumsRYN98WIpIlnAwsmL1G-GQChskzAQa5M8u2m7rNKeY1JNNYEp_Nlm6u2vZwwXfy6g6Qu5s0Z7PANNTBTs3b_94dvRjC_FbqugBNG4NX5bfI7a8Svh9zAz5F/s559/wang-fcc_kr.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="31" data-original-width="559" height="22" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEikKT15qFkOQYpfDk4Q2-tjJDjfwcIpJq-oErnUk9mrBs1GWC4-uZrhY_m3N0Aze3du0azumsRYN98WIpIlnAwsmL1G-GQChskzAQa5M8u2m7rNKeY1JNNYEp_Nlm6u2vZwwXfy6g6Qu5s0Z7PANNTBTs3b_94dvRjC_FbqugBNG4NX5bfI7a8Svh9zAz5F/w400-h22/wang-fcc_kr.jpg" width="400" /></a></div><div style="text-align: left;"><br /></div><div style="text-align: left;">Refer to the previous discussion of Kr, above, in the Wang equation. Their usage is identical.<br /><br />Wang again recommends that the geomagnetic mid-point latitude, ThetaM, be between -60 (south) and +60 degrees (north). It is not dependent on frequency.<br /><br /><b>ITU FORMULA DETAILS</b><br /><br />The ITU expression for field strength is:<br /><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEinmUBuWqyReyg8HbrbDNo8KNLSSvfzRCxU3jyG38D-FyIeAELH7025Rz2zxYDA6HFyJyLza0cSJcCLsFX32c1jePO2bWDeYEXK671sY_4JX-FYN2-FDRFMpEID6MRQ7QhsmMFgW9YTlE9hy9qddsqXI16PE-X-f5MUTnsJijvytzljNsFNPONZ3vtU6Kb4/s946/itu_formula.jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" data-original-height="32" data-original-width="946" height="22" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEinmUBuWqyReyg8HbrbDNo8KNLSSvfzRCxU3jyG38D-FyIeAELH7025Rz2zxYDA6HFyJyLza0cSJcCLsFX32c1jePO2bWDeYEXK671sY_4JX-FYN2-FDRFMpEID6MRQ7QhsmMFgW9YTlE9hy9qddsqXI16PE-X-f5MUTnsJijvytzljNsFNPONZ3vtU6Kb4/w640-h22/itu_formula.jpg" width="640" /></a></div><br /><div style="text-align: left;"><br /></div><div style="text-align: left;">Note: FS(dBu), is also known as dBµV/m.<br /><br />Where: FS(dBu) is the field strength in dBµV/m, V is the transmitter cymomotive force above (or below) the reference 300 mV in dB, Gs is the sea gain correction in dB, Lp is the excess polarization coupling loss in dB (defined graphically in ITU Recommendation 435-7), ThetaM is the mid-point transmitter and receiver geomagnetic latitude, Dslant is the slant distance in km. Kr, or generalized ionospheric losses, are described below.<br /><br />Converting to millivolts per meter, again:<div class="separator" style="clear: both; text-align: center;"><br /></div></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div style="text-align: left;"><b>mV/m = 10 ^ (FS(dBu) / 20) / 1000 ...convert dBu back to mV/m</b></div></blockquote><div style="text-align: left;"><br />The ITU formula applies the basic path loss elements, the slant distance and the mid-point geomagnetic latitude influence. It also attempts to quantify some of the additional ionospheric losses I alluded to in an earlier post:<br /><br /></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px; text-align: left;"><div style="text-align: left;">1. Sea gains (separately, as Gs)</div><div style="text-align: left;">2. Excess polarization coupling losses (separately, as Lp)</div><div style="text-align: left;">3. Sunspot influence (specified within Kr, as R)</div><div style="text-align: left;">4. Regional loss due to solar activity (calculated within Kr, as bsa * R)</div></blockquote><div style="text-align: left;"><br />The generalized ionospheric losses are found in the ITU's Kr factor:<br /><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxmYIAEm82WAP00nOWiJUljSCkzkesDnwhvOimWr4x-hudg5r3o3W6fmxgVeJUeIJR5IfCzT7USGF35RnSikuXbCdTHKYhsqtciEBAdUDLaPJkEV_O5XoBjpevfwmbGUWN2bt9sXOmiE_p6gQosAlPUd1ZD_LqtwZ3Rb_tqBo29dMAXElEQZ0MtrEQBSDZ/s577/itu_kr.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="32" data-original-width="577" height="23" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxmYIAEm82WAP00nOWiJUljSCkzkesDnwhvOimWr4x-hudg5r3o3W6fmxgVeJUeIJR5IfCzT7USGF35RnSikuXbCdTHKYhsqtciEBAdUDLaPJkEV_O5XoBjpevfwmbGUWN2bt9sXOmiE_p6gQosAlPUd1ZD_LqtwZ3Rb_tqBo29dMAXElEQZ0MtrEQBSDZ/w400-h22/itu_kr.jpg" width="415" /></a></div><div style="text-align: left;"><br /></div><div style="text-align: left;">Kr is the loss factor in dB, to include ionospheric absorption, focusing and terminal losses, and losses between hops, geomagnetic latitude factor, and basic polarization coupling loss. Unlike the Wang and FCC formulas, the ITU formula incorporates a sunspot factor and a frequency factor as well.<br /><br />Where: f is the frequency in kHz, and ThetaM is the geomagnetic latitude defined previously. ThetaM must not exceed 60 degrees north or -60 degrees south. For paths shorter than 3000 km, the ITU suggests simply using the geographic mid-point between transmitter and receiver. Note: this, on average, skews results about 6 dB higher for North America.<br /><br />Where: R is the twelve-month smoothed international relative sunspot number, bsa is the regional solar activity factor (bsa=0 for LF band; bsa=4 for MF band for North American paths, 1 for Europe and Australia, and 0 elsewhere). For paths where the terminals are in different regions we use the average value of bsa, for example: Europe to the USA, 2.5.<br /><br />Note that we have a frequency correction, a geomagnetic latitude (ThetaM) correction, a regional correction in bsa (North America has the highest absorption), and a sunspot count correction.<br /><br />The sharp analyst will notice that the ITU's frequency correction results in greater loss at higher frequencies, something perhaps theoretically sound, but not observed in North America (shown by measurements). The ITU suggests that for North America, a fixed frequency of 1000 kHz should be used.<br /><br />Sea gain (Gs) is included in the ITU formula, but is usually set to zero and not accounted for since the transmitting or receiving station must be very close to a coastal point, generally within ten kilometers, and having a path length of thousands of kilometers. Lp, excess polarization coupling loss, is also included. This is an attempt to compensate for Lp differences in the generalized Kr part of the formula. We generally leave this at zero.<br /><br /><b>CAIRO CURVES FORMULA DETAILS</b><br /><br />The modern day formula for the Cairo curve, adapted to Region 2, is presented for informational purposes. The resultant field strength should be further modified by subtracting ionospheric absorption losses (Kr), and adding any antenna gain.<br /><br />The Cairo Curve, Revised for North America, Region 2<br /><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEir3vUN3AQfhVWJzPYm4WBQNP6Bz2tVJj9ID_5kmYAvJkOXvNhk8wFJAplKf7xG4PkAtFFGTOIPo9ETcz-8XFHHy0ZO0hxJxEcl2LVR83TvWTpQ26er_QhDaoMAEj44BsoG5UHEAVnfJH4upbuUbel9WDLpQD_FiVfYbNgbi7XVgl8msq2x7K0yiKGiJ5j5/s366/cairo_formula.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="32" data-original-width="366" height="23" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEir3vUN3AQfhVWJzPYm4WBQNP6Bz2tVJj9ID_5kmYAvJkOXvNhk8wFJAplKf7xG4PkAtFFGTOIPo9ETcz-8XFHHy0ZO0hxJxEcl2LVR83TvWTpQ26er_QhDaoMAEj44BsoG5UHEAVnfJH4upbuUbel9WDLpQD_FiVfYbNgbi7XVgl8msq2x7K0yiKGiJ5j5/w320-h29/cairo_formula.jpg" width="263" /></a></div><div style="text-align: left;"><br /></div><div style="text-align: left;">Where D is the overland great circle distance in kilometers between transmitter and receiver.</div><div style="text-align: left;"><br /></div><div style="text-align: left;">Again, we find our result in dBu per 100 mV/m (NTIA Report 99-368). It must be converted back to actual mV/m, as does the FCC formula.</div><div style="text-align: left;"><br /></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div style="text-align: left;"><b>mV100 = 10 ^ (FS(dBu) / 20) / 1000 ...convert dBu back to mV/m</b></div></blockquote><div style="text-align: left;"><br /></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div style="text-align: left;"><b>mV/m = mV100 * (measured_mVm@1km / 100) ...corrected to actual mV/m</b></div></blockquote><div style="text-align: left;"><br /></div><div style="text-align: left;">In the final part of this series on skywave prediction we will wrap up by discussing polarization coupling loss, sea gain, solar cycle losses, and diurnal and seasonal effects on mediumwave propagation.<br /><br /></div>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com0tag:blogger.com,1999:blog-4260200412608523752.post-19298806340959497992023-08-12T08:59:00.002-04:002023-08-12T09:01:20.415-04:00AM Radio In South America<p>I've been working on compiling a list of world AM broadcast radio (530-1700 kHz) still on the air. South America is essentially complete. The goal is a worldwide list of stations and locations.</p><p>Here is what is left of AM broadcast radio in South America as of this date, August 2023.</p><p>Click image for the larger view.</p><p><br /></p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhM6PNkarrsmGyCejl94yzEIYkQew1Ta-MYNHgWm0f8F5zViEIeX0VBChIaXheSWK3cF1OC5GZQSF47z_mGgAEaQ7ZmYub-2zSJ9u4jrmjXJS3KtAFtKUQ1_q4VB8WukHz2CjVyLkFf2E_N41dkY3hm0Xv2M5ML3Ty2Rjbj6Cy_OuNcJhVYx1b3foLL7AtN/s966/south_american_AM.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="966" data-original-width="760" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhM6PNkarrsmGyCejl94yzEIYkQew1Ta-MYNHgWm0f8F5zViEIeX0VBChIaXheSWK3cF1OC5GZQSF47z_mGgAEaQ7ZmYub-2zSJ9u4jrmjXJS3KtAFtKUQ1_q4VB8WukHz2CjVyLkFf2E_N41dkY3hm0Xv2M5ML3Ty2Rjbj6Cy_OuNcJhVYx1b3foLL7AtN/w504-h640/south_american_AM.jpg" width="504" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">AM Broadcast Radio, 2023</td></tr></tbody></table><br /><p><br /></p>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com0tag:blogger.com,1999:blog-4260200412608523752.post-49482343555071871302023-07-22T10:43:00.016-04:002023-07-22T10:51:30.049-04:00Mediumwave Skywave Prediction #4 - Slant Distance & Geomagnetic LatitudeWe will define two important concepts in this article: Slant Distance and Geomagnetic Latitude, both critical to determining the base path loss factor. This is our first step in solving the mediumwave skywave prediction puzzle.<br /><br />To review, here are our main formulas again.<br /><br /><div style="text-align: center;"><u>The Wang Method:</u></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgiVVAUgiV5UW88bO3LQlDrB5Xll1iqSs7hLvZr-BSBuv1JyUegz3wDNUv-XghJ2nv_lhR1-a-VBN3q9D7bMlB91T6HHr_JZrgCrY3wR-B1Yqw0f-91jJaLcPPHKRAGozgbmr1qJ6RkP6G13M8vP6e4aPV9o53jSfTFbBalvZXe4ij62TQP5ilpitbciDbD/s471/wang_formula.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="32" data-original-width="471" height="22" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgiVVAUgiV5UW88bO3LQlDrB5Xll1iqSs7hLvZr-BSBuv1JyUegz3wDNUv-XghJ2nv_lhR1-a-VBN3q9D7bMlB91T6HHr_JZrgCrY3wR-B1Yqw0f-91jJaLcPPHKRAGozgbmr1qJ6RkP6G13M8vP6e4aPV9o53jSfTFbBalvZXe4ij62TQP5ilpitbciDbD/w320-h22/wang_formula.jpg" width="320" /></a></div><div><br /></div><div style="text-align: center;"><u>The FCC Method:</u><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhtysINTLyu417CDUasX1ooYu0O-6yOWxoOxuj76RKFg58RS8waNLt4dSZUQ5axmHRirR67H4i5wiEj0wwZrsH4THKaZkqX0TTSbV4Z1kdNLth-fLwyww9IQs2fkJsKeYINZKdY4gYn-4i1pd1mcAXt_KK7Kro67fNXgUEQyZbulDfMUQuaFi6IH_UtzRSQ/s431/fcc_formula.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="32" data-original-width="431" height="24" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhtysINTLyu417CDUasX1ooYu0O-6yOWxoOxuj76RKFg58RS8waNLt4dSZUQ5axmHRirR67H4i5wiEj0wwZrsH4THKaZkqX0TTSbV4Z1kdNLth-fLwyww9IQs2fkJsKeYINZKdY4gYn-4i1pd1mcAXt_KK7Kro67fNXgUEQyZbulDfMUQuaFi6IH_UtzRSQ/w320-h24/fcc_formula.jpg" width="320" /></a></div><div><br /></div><div style="text-align: center;"><u>The ITU Method:</u></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEglgpYg_cfxhzDNrCpm0ik1ASICxw2ydvii2DVbcBWnR8uDc6_gZxHVkwPtz320dfAN3z1XKZpRiphFpMAGDrqqJV-NPVQflT3sHMRoRY4V2qrgKyPgD8OEl1YRiVh5vvy_BUZtcFIBE0DMdFJmOkLx3m2jjFsQJEM9hz-8gT_Z0lOUuV1pB1wcNhIbAYnK/s946/itu_formula.jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" data-original-height="32" data-original-width="946" height="22" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEglgpYg_cfxhzDNrCpm0ik1ASICxw2ydvii2DVbcBWnR8uDc6_gZxHVkwPtz320dfAN3z1XKZpRiphFpMAGDrqqJV-NPVQflT3sHMRoRY4V2qrgKyPgD8OEl1YRiVh5vvy_BUZtcFIBE0DMdFJmOkLx3m2jjFsQJEM9hz-8gT_Z0lOUuV1pB1wcNhIbAYnK/w640-h22/itu_formula.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div><b><br /></b></div><div><b>SLANT DISTANCE</b><br /><br />The skywave field strength calculation process must compute a path loss factor between transmitter and receiver. Several parameters come into play here. The obvious one is the distance between transmitter and receiver. Greater distance incurs greater loss, plainly evident to the early experimenters. For many years the great circle overland distance was used in all formulas. It was eventually found that the actual distance traveled by the signal, the slant distance, was a better fit and produced better figures, as the signal must travel from transmitter to the reflection point high up in the ionosphere, then back down to the receiver. This, the preferred distance, is referred to as the Dslant distance in the formulas.<br /><br />Slant distance is easily calculated for any signal path. From the FCC document 47 CFR 73.190:<br /><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgLr3MMpn9Pmxc5BFei3tvkGwwT345Yo-xZkEe2legBb3j7ev_1FHGjQqyJiUVY8PK9QiwyDnW-8-YJ825c6qEZ1rlflJyVj73pV0ccIGD8qiQ-IkH_gNml7hV9TkgpMmjGyhgugM4hjTQrjGu8h6i3XRfkdJauBOPvIAe5NYVWsbLVFleWsV8I_z3mJCXV/s269/Dslant.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="32" data-original-width="269" height="24" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgLr3MMpn9Pmxc5BFei3tvkGwwT345Yo-xZkEe2legBb3j7ev_1FHGjQqyJiUVY8PK9QiwyDnW-8-YJ825c6qEZ1rlflJyVj73pV0ccIGD8qiQ-IkH_gNml7hV9TkgpMmjGyhgugM4hjTQrjGu8h6i3XRfkdJauBOPvIAe5NYVWsbLVFleWsV8I_z3mJCXV/w200-h24/Dslant.jpg" width="200" /></a></div><div><br /><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px; text-align: left;">' D is the overland great circle distance from transmitter to receiver.<br />' hr is the ionospheric layer height in kilometers. For mediumwave, usually set to 100.</blockquote><br />Let's do a few examples. We will see that the higher the reflective layer height, the greater the slant distance. For added interest I've calculated TA, shown below, which is the signal takeoff angle from the antenna.<br /><br />At 275 km overland distance, slant distance can deviate greatly. Takeoff angle is also large:<br /><br /><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px; text-align: left;">' 275 km distant station and a 100 km layer height, Dslant = ~340 km, TA=35°<br />' 275 km distant station and a 120 km layer height, Dslant = ~365 km, TA=40°<br />' 275 km distant station and a 150 km layer height, Dslant = ~407 km, TA=46°</blockquote><br />At 1000 km overland distance, slant distance is only just a little greater. Takeoff angle has come way down:<br /><br /><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px; text-align: left;">' 1000 km distant station and a 100 km layer height, Dslant = ~1019 km, TA=9°<br />' 1000 km distant station and a 120 km layer height, Dslant = ~1028 km, TA=11°<br />' 1000 km distant station and a 150 km layer height, Dslant = ~1044 km, TA=14°</blockquote><br />And slant distance is basically negligible at 2000 km. Takeoff angle is right at the horizon:<br /><br /><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px; text-align: left;">' 2000 km distant station and a 100 km layer height, Dslant = ~2009 km, TA=1°<br />' 2000 km distant station and a 120 km layer height, Dslant = ~2014 km, TA=2°<br />' 2000 km distant station and a 150 km layer height, Dslant = ~2022 km, TA=4°</blockquote><br />Out past about 900 km or so, the slant distance is very close to the actual overland distance. As we get closer in from 900 km, the difference starts to accelerate. The Dslant distance value is dependent on the E-layer height and Dslant (in km) is always higher than the exact overland distance value. Slant distance is now commonly used in all modern skywave formulas.<br /><br />This slant distance is used in two places in the formulas. It becomes part of the basic path loss factor, and part of the ionospheric loss adjustment (the Kr term). In the basic calculation, the larger the slant distance, the greater the basic path loss factor. Secondly, and since the ionospheric losses are subtracted from the basic path loss, the larger the slant distance, the greater the effect it has on ionospheric losses, Kr.<br /><br />Ionospheric losses, Kr, will be explained in further detail in the next article.<br /><br />Each formula uses the inverse square law in the basic path loss calculation. This will be in dB. This simply says that for every doubling of distance, the strength is one-fourth of what it was. For example, the strength at 1000 km is one-fourth the strength found at 500 km. This is realized through the formula snippet <i><b>20 * Log10(Dslant)</b></i>. 20x gives us the value needed in dBµV/m to subtract from our start value since we are dealing with field strength in voltage units.<br /><br />Here are some path loss examples for a layer height of 100 km:<br /><br /><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px; text-align: left;">Dslant = 250 km = 48 dB (190 km overland distance)<br />Dslant = 500 km = 54 dB (458 km overland distance)<br />Dslant = 1000 km = 60 dB (980 km overland distance)<br />Dslant = 2000 km = 66 dB (1990 km overland distance)</blockquote><br />Each doubling of distance increases the loss by another 6 dB, also one S-unit. The Dslant contribution to the basic path loss is subtracted from our start value of 106.6 dB (ITU), (107 dB, Wang), (97.5 dB, FCC).<br /><br />In the ITU formula <i><b>(- 0.001 * Kr * Dslant)</b></i>, Dslant again modifies the ionospheric losses, Kr. So, as you can see, the greater the slant distance, the greater its contribution to the ionospheric losses too.<br /><br />Wang handles the ionospheric losses, Kr, a little differently <i><b>(- Kr * Sqrt(Dslant / 1000)</b></i>. Dslant again modifies Kr. We can see again the greater the slant distance, the greater its contribution to ionospheric losses.<br /><br />Wang's Kr value modification by Dslant is used the same way in the FCC formula.<br /><br /><b>PERSONAL OBSERVATIONS GAINED FROM TESTING</b><br /><br />Using the Dslant value has minimal effect on far stations, those out beyond 900 km or so, where Dslant is roughly equal to the exact distance value. An increasingly greater effect is evident on those stations as we narrow our distance to 250 km, and less.<br /><br />A continuing problem still exists with accuracy for close in stations. Years ago, Wang suggested those stations less than 250 km distant should use a fixed E-layer height of 220 km, increasing the resultant Dslant value even more. That fixes the lowest slant distance at 506 km for any station closer than 250 km to the receiver. Consequently, 250 km becomes a hard "wall" which would make a station's calculated field strength at 251 km much stronger than one at 249 km. Nature undoubtedly has a proportional transition which must be accommodated.<br /><br />It would be obvious that increasing the layer height also increases the transmitter signal's takeoff angle, generally resulting in a weaker facing signal to the receiver, resulting in the calculation further lowering the received field strength. By design, this was Wang's intent in raising the layer height to 220 km for stations closer than 250 km distance. It was not enough.<br /><br /><b><u>Experimenting.</u></b><br /><br />The remaining paragraphs in this, the Slant Distance section, are ideas outside of the current formulas, and are food for thought. In my program which creates the mediumwave pattern map set, RDMW (Radio Data MW), I wrote a sandbox mode which allows me to experiment with different skywave propagation ideas. These include varying layer heights, varying attenuation factors, seasonal effects, and sunrise/sunset enhancements. Tweaks can be modified by frequency also. It has revealed some interesting facts.<br /><br />Part of the problem with the current worldwide formula set is that, given a database of stations like the FCC mediumwave database, it will produce an acceptable list of varying field strengths, but the field strength order, channel by channel, isn't always what is heard during actual band scanning. I tested this on all three formulas and found this curious.<br /><br />Material written is very explicit indicating that the E-layer is well-defined and exists between about 100 km and 115 km. Mediumwave skywave is considered (by formula) to be reflected or refracted off the E-layer at 100 km exclusively. I do not believe this to be the case, and it is borne out by the inaccuracies in the formulas for close in stations, those about 900 km and closer.<br /><br />Modifying the layer height has been experimented with extensively, generally by raising it incrementally as we get closer and closer to the transmitter, starting at about 900 km and modifying by the inverse cosine of the distance. Results were better, bringing field strengths more in line. Still, the resultant skywave calculations using this method did not quite match signal strengths by band scanning. Actual signals are always less for close in stations, except at the sunrise/sunset enhancement periods where they exhibit a temporary strengthening.<br /><br />A gentle transition of E-layer reflectivity height from 100 km to 280 km (acknowledged, 280 km is outside of the E-layer) is suggested, starting at 100 km with station distances about 900 km and raising it as we get closer to zero distance using an inverted cosine method. However, a maximum layer height of 280 km does not fully correct the field strength inaccuracy. We must add in an additional decay factor as the station distance is decreased. I would advise against increasing maximum layer height beyond 280 km as I think it presents an increasingly inaccurate picture of conditions.<br /><br /><b><u>An inverted waveguide?</u></b><br /><br />The Earth's natural waveguide effect is well known for extremely low frequencies (ELF), those below 3 kHz. What if, instead, we treat the ionosphere from 100 to 140 km as a sort of mediumwave inverted waveguide? That is, make our reflecting layer heights dynamic - the lower frequencies (starting at 530 kHz) reflecting at the lowest layer height, and higher frequencies (ending at 1700 kHz) reflecting at highest layer height? We could set a layer height range of 100 to 140 km to fully contain all reflections within the banded E-layer. Or, we might even experiment with a range of 100 to 300 km to allow higher frequency reflections at the F-layer. The first scenario was experimented with and seems most promising. It delivers surprisingly good field strength results verified by what is actually heard by band scanning.<div><br /></div><div><b><u>Skip distance.</u></b></div><div><br /></div><div>Many of you, when studying radio propagation, will see charts or graphics showing a single hop track up to the ionosphere and reflected back to Earth. Sometimes beneath it are printed the words, "Skip Distance". They are referring to a zone of dead signal, that is, an area where the signal is "skipping overhead", and not receivable in the skip zone. Take care to note this applies almost exclusively to shortwave frequencies, that of 3 MHz and above, and hardly at all to mediumwave. Mediumwave tends to "fill in" in the skip zone, at varying levels. Nighttime skip reflections are detectable and receivable at very short distances, even under 60 km.<br /><br /><b>TAKEOFF ANGLE</b><br /><br />For the curious, those wanting to calculate signal takeoff angle from a transmitter, this simple program will calculate it. Choose your layer height (hr) and your distance from receiver to transmitter (km).<br /><br /></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px; text-align: left;"><div><span style="font-family: courier;">Pi = 3.14159</span></div><div><span style="font-family: courier;">hr = 100 'layer height, km</span></div><div><span style="font-family: courier;">km = 900 'great circle distance, km</span></div><div><span style="font-family: courier;">D = km / 40075 * 2 * Pi '40075=circumference of earth, km</span></div><div><span style="font-family: courier;">E = 6378 * Sin(D / 2) '6378=radius of earth, km</span></div><div><span style="font-family: courier;">F = E / Tan(Pi / 2 - D / 4)</span></div><div><span style="font-family: courier;">G = Atn(F / E + hr / E) - D / 2</span></div><div><span style="font-family: courier;">TA = G / Pi * 180 'TA in degrees</span></div></blockquote><div><br />Takeoff angle is important. The ITU and Wang formulas include a basic gain/loss correction in dB referenced to 1 KW effective radiated power, ERP (the V cymomotive force parameter), but don't allude to any differences due to signal takeoff angle. The FCC formula accounts for the gain/loss correction in a different way, by normalizing its returned field strength value to 100 mV/m at 1 KW, still not alluding to any differences due to signal takeoff angle.<br /><br />I'll show you an example of how ignoring takeoff angle can produce highly inaccurate results. We'll look at WBVP-1230 (1 KW) in Beaver Falls, PA. WBVP uses a single monopole tower at 0.64 wavelength tall. Their skywave signal takeoff angle from their antenna to Rochester, NY is 29.2 degrees, based on an E-layer height of 100 km, a substantial angle. If we ignore takeoff angle and assume to use their full 1 KW ERP (which we would only see at 0 degrees takeoff angle), we are calculating field strength at 1 KW "facing watts", that is, the ERP at the horizon, facing us. This isn't reality.<br /><br />The reality is that our received signal is being delivered from the 29.2 degree angle, a very different effective radiated power than the angle at the horizon. At 29.2 degrees takeoff angle, with WBVP we only "see" 34 watts coming at us. WBVP will show up at very much less field strength on the dial than other stations because of this. Power differences because of elevated takeoff angle makes a huge difference in our calculation process and our resulting received field strength. It must be accounted for.<br /><br />We move on to geomagnetic latitude and longitude.<br /><br /><b>GEOMEGNETIC LATITUDE & LONGITUDE</b><br /><br />Normal latitude and longitude is referenced to as the north (or south) geographic pole, an actual latitude of 90°, and respectively, -90°. Longitude at the poles is irrelevant as they all converge at this point. Geomagnetic latitude and longitude uses the geomagnetic poles as our north-south reference instead. Geomagnetic poles (dipole poles) are the intersections of the Earth's surface and the axis of a bar magnet hypothetically placed at the center the Earth by which we approximate the geomagnetic field. They differ greatly from the magnetic poles, which are the points at which magnetic needles become vertical. The magnetic poles are what has been "wandering", a subject in the news lately, but they drag the geomagnetic poles with them too, albeit at a lesser rate.<br /><br />Imagine our Earth where the north pole was instead the geomagnetic north pole, currently (2023) in the extreme northwest corner of Greenland. The Earth's longitude lines would all emanate from that point, and it would be considered 90 degrees north latitude. The geomagnetic latitude of New York City, for example, would then be referenced to the geomagnetic north pole, not the actual north pole.<br /><br />So, the result is this. Instead of New York City being at 40.75°N latitude actual, NYC is now at 49.95°N geomagnetic latitude. This makes a tremendous difference in our mediumwave skywave prediction. The geomagnetic north pole is where the auroral zone is centered in the northern hemisphere. The auroral zone greatly affects the mediumwave signal.<br /><br />Geomagnetic location is sometimes called the geomagnetic dipole. Both the geomagnetic and magnetic poles have been wandering quite a bit over the last few years. In 1950 the geomagnetic pole was located at approximately 78.5°N and 68.8°W. Today, 2023, it has moved 4 degrees farther north and 2 degrees farther west. Here are the current and future predicted locations:<br /><br />From website: <a href="https://wdc.kugi.kyoto-u.ac.jp/poles/polesexp.html">https://wdc.kugi.kyoto-u.ac.jp/poles/polesexp.html</a><br /><br /> Geomagnetic dipole (Northern hemisphere):<br /><br /></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px; text-align: left;"><div><span style="font-family: courier;"> 2022 80.7°N 72.7°W</span></div><div><span style="font-family: courier;"> 2023 80.8°N 72.7°W</span></div><div><span style="font-family: courier;"> 2024 80.8°N 72.6°W</span></div><div><span style="font-family: courier;"> 2025 80.9°N 72.6°W</span></div></blockquote><div><br />So, in skywave analysis, first we must calculate the reflected signal's mid-path latitude and longitude and convert it to its geomagnetic reference. The mid-point latitude and longitude, before conversion, is generally half the distance between transmitter and receiver on a great circle line drawn between the two. We assume the geomagnetic north pole to be our new north pole at 90 degrees latitude. We first calculate the actual latitude and longitude of the path mid-point (the reflection point) between transmitter and receiver and reference its latitude (in degrees offset) to the geomagnetic north pole.<br /><br />This mid-path latitude is then used in two places in the formulas. It becomes part of the basic path loss calculation, and part of the ionospheric losses (the Kr term). In the basic calculation, the higher the geomagnetic latitude, the greater the extra losses incurred. Secondly, and since the ionospheric losses are subtracted from the basic path loss, the higher the geomagnetic latitude, the greater the additional losses incurred.<br /><br />In the ITU formula, the formula snippet <i><b>2 * Sin(ThetaM)</b></i> establishes the basic geomagnetic loss relative to the path mid-point. At 40 degrees geomagnetic north latitude it is 1.28 dB, while at 60 degrees north it is 1.73 dB. So we see about a 0.5 dB difference (loss). Wang treats it differently, using <i><b>Tan^2(ThetaM)</b></i>. In Wang's formula, and also the FCC formula, at 40 degrees geomagnetic north latitude the loss is 0.7 dB, where at 60 degrees north the loss is 3.0 dB. Wang is allowing greater compensation for North America as the mid-point approaches 60 degrees north.<br /><br />In the next article we'll dive right into the formulas and put it all together.<div><br /></div></div></div>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com0tag:blogger.com,1999:blog-4260200412608523752.post-79632845074149995342023-07-14T06:40:00.024-04:002023-07-22T11:03:00.697-04:00Mediumwave Skywave Prediction #3 - Introduction To Formulas<span style="font-family: arial;">Now that we've covered skywave prediction history in this series, let's look at a few actual formulas which are used to calculate skywave field strength. This will likely spill over into several articles as we describe the concepts and intricacies of skywave propagation.<br /><br /><b>THE SURVIVORS</b><br /><br />By the turn of the millennium, three simplified formulas survived and are usable for worldwide mediumwave skywave field strength prediction. They each have viable options to consider.<br /><br />They are:<br /></span><div><div><span style="font-family: arial;"><br /></span><div style="text-align: center;"><span style="font-family: arial;"><u>The Wang Method:</u></span></div></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhNU9w2gIM-PoYhT29MO2L1haOEMo7lX3Rtr8haRIX09Q-eyCTs2K8cSlbDULZxl0iTYSS0qrHOKmb_M9EHcy5bJLWEAgqD3NazoueVQGBP6vq3qaec4v9WfFLUqFT8ZC-ZvNC4gqah_YIi1Bruhyf89w9AhrDnrfdEFgy9RRQTIlWtZo2674rLoW_jiLBi/s471/wang_formula.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="32" data-original-width="471" height="22" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhNU9w2gIM-PoYhT29MO2L1haOEMo7lX3Rtr8haRIX09Q-eyCTs2K8cSlbDULZxl0iTYSS0qrHOKmb_M9EHcy5bJLWEAgqD3NazoueVQGBP6vq3qaec4v9WfFLUqFT8ZC-ZvNC4gqah_YIi1Bruhyf89w9AhrDnrfdEFgy9RRQTIlWtZo2674rLoW_jiLBi/s320/wang_formula.jpg" width="320" /></a></div><div><br /></div><div><div style="text-align: center;"><span style="font-family: arial;"><u>The FCC Method:</u></span></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjVBnESxNgfpUlTogl7ivO4-bBqiiBVVcD-4_4ADvk1DnvZ69wmDGTpJiprTDHSWsVyIKDxWlrmp9m5cVrlrPR5R3nOGsIzX2hlPunJJpPvNt2WfcNnxGZ8G67uY1N8ttq0fkaCjUHbfEnGqGPL-mPEaEXUq47KCLy2GgmSCip20bI9clKaKlfIcG4WHwRP/s431/fcc_formula.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="32" data-original-width="431" height="24" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjVBnESxNgfpUlTogl7ivO4-bBqiiBVVcD-4_4ADvk1DnvZ69wmDGTpJiprTDHSWsVyIKDxWlrmp9m5cVrlrPR5R3nOGsIzX2hlPunJJpPvNt2WfcNnxGZ8G67uY1N8ttq0fkaCjUHbfEnGqGPL-mPEaEXUq47KCLy2GgmSCip20bI9clKaKlfIcG4WHwRP/s320/fcc_formula.jpg" width="320" /></a></div><div><br /></div><div style="text-align: center;"><span style="font-family: arial;"><u>The ITU Method:</u></span></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiUP9P0SdZAbK5vSjmQiYRXiF-u-YVoyjYL9QOprxHzr3_SdWLhe0VD76Q2NsuY6pPFYyJbzeWjtzq64-Yt9GK9CiDZkGNYHgcoFGrvu9i7tuLNlOlv_AICOuQbsTOYbWLXnIXMOwyplLYsM1XvGASTGlO4h0OuhUXYlR6BFF9Q98m6M02jH0MP44kGmnRg/s946/itu_formula.jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" data-original-height="32" data-original-width="946" height="22" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiUP9P0SdZAbK5vSjmQiYRXiF-u-YVoyjYL9QOprxHzr3_SdWLhe0VD76Q2NsuY6pPFYyJbzeWjtzq64-Yt9GK9CiDZkGNYHgcoFGrvu9i7tuLNlOlv_AICOuQbsTOYbWLXnIXMOwyplLYsM1XvGASTGlO4h0OuhUXYlR6BFF9Q98m6M02jH0MP44kGmnRg/w640-h22/itu_formula.jpg" width="640" /></a></div><br /></div><div><br /></div><div><br /></div><div><span style="font-family: arial;">Yes, they look cryptic at this point. Not to worry, we'll take these apart, item by item, and show you what they're attempting to do.<br /><br />Where the ITU method attempts to provide a generalized worldwide formula, both the Wang and FCC methods are specialized for Region 2, the Americas, and specifically North America. It must be stressed that these are so-called "simplified formulas", though they do their job quite well. To wit, all have simplified the calculation process associated with hop loss, polarization coupling loss, and solar effects, boiling these down into a generalized expression, Kr. We will analyze Kr in due course.<br /><br /><b>DISSECTING THE FORMULAS</b><br /><br />Each of the these formulas can be sub-divided into three parts.<br /><br />They are:</span></div><span style="font-family: arial;"><br /></span></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div style="text-align: left;"><div style="text-align: left;"><span style="font-family: arial;">1. Calculate a base path loss factor which is based on the path distance. Dslant in the formulas.</span></div></div></blockquote><div><div style="text-align: left;"><span style="font-family: arial;"><br /></span></div></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div><div style="text-align: left;"><span style="font-family: arial;">2. Calculate the extra loss due to the path's geomagnetic mid-point relative to the geomagnetic north pole. ThetaM in the formulas.</span></div></div></blockquote><div><div style="text-align: left;"><span style="font-family: arial;"><br /></span></div></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div><div style="text-align: left;"><span style="font-family: arial;">3. Finally, factor in any additional losses/gains like frequency, sea gain, and basic values for ionospheric absorption, polarization coupling losses, focusing and terminal losses, and losses between hops, sunspot number and solar activity. Kr in the formulas.</span></div></div></blockquote><div><div style="text-align: left;"><span style="font-family: arial;"><br />These additional losses or gains (items 2 and 3), in dB, are subtracted from or added to the base path loss factor to arrive at a final overall path loss value. The final result of the above calculations then give us a ballpark field strength for the midnight hour, or what is usually called SS+6, or sunset+6 hours. This is directly translated into dBµV/m, or dB relative to 1 microvolt per meter, the predicted field strength available at the receiver. <br /><br />We may or not choose to continue on with even more losses or gains, not shown in the formulas above. If we do, these extras can be:<br /><br /></span></div></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div style="text-align: left;"><div style="text-align: left;"><span style="font-family: arial;">• Diurnal hourly losses/gains (skywave prediction for the hour of the day). </span></div></div></blockquote><div style="text-align: left;"><div style="text-align: left;"><span style="font-family: arial;"><br /></span></div></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px; text-align: left;"><span style="font-family: arial;">• Sunrise and sunset enhancements (skywave prediction at these critical hours).</span></blockquote><div><span style="font-family: arial;"><br /></span></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div style="text-align: left;"><span style="font-family: arial;">• Seasonally-driven losses/gains (skywave prediction for winter versus summer).</span></div></blockquote><div><div><div style="text-align: left;"><span style="font-family: arial;"><br />So, let's gather all the pieces we need to solve the prediction puzzle. We will ignore the extras for now.<br /><br /><u>The Basics:</u><br /><br /></span></div></div></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div><div><div style="text-align: left;"><span style="font-family: arial;">1. Calculate Dslant, the "slant distance" and use it to derive a basic path loss factor (a new term - we use slant distance instead of the great circle distance from transmitter to receiver).</span></div></div></div></blockquote><div><div><div style="text-align: left;"><span style="font-family: arial;"><br /></span></div></div></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div><div><div style="text-align: left;"><span style="font-family: arial;">2. Calculate ThetaM, the mid-point geomagnetic latitude, also part of the basic path loss factor.</span></div></div></div></blockquote><div><div><div style="text-align: left;"><span style="font-family: arial;"><br /><u>The Ionospheric Tweaks (all but Sea Gain calculated within the Kr term):</u><br /><br /></span></div></div></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div><div><div style="text-align: left;"><span style="font-family: arial;">3a. Choose the ionospheric layer height (usually 100 km).</span></div></div></div></blockquote><div><div><div style="text-align: left;"><span style="font-family: arial;"><br /></span></div></div></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div><div><div style="text-align: left;"><span style="font-family: arial;">3b. Account for Hop losses.</span></div></div></div></blockquote><div><div><div style="text-align: left;"><span style="font-family: arial;"><br /></span></div></div></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div><div><div style="text-align: left;"><span style="font-family: arial;">3c. Account for Sea Gain (usually ignored).</span></div></div></div></blockquote><div><div><div style="text-align: left;"><span style="font-family: arial;"><br /></span></div></div></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div><div><div style="text-align: left;"><span style="font-family: arial;">3d. Account for Polarization Coupling losses.</span></div></div></div></blockquote><div><div><div><span style="font-family: arial;"><br /></span></div></div></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px;"><div><div><div style="text-align: left;"><span style="font-family: arial;">3e. Account for Sunspots & solar activity.</span></div></div></div></blockquote><div><div><div><span style="font-family: arial;"><br />Let's first describe the ionosphere at mediumwave and how our signal is reflected or refracted back to Earth. Later on we'll define two important concepts: Slant Distance and Geomagnetic Latitude, both critical to determining the base path loss factor.<br /><br /><b>IONOSPHERIC LAYERS</b><br /><br />Nighttime mediumwave propagation has long been assumed to be reflected or refracted off the E-layer of the ionosphere. The ionosphere is layered as we go skyward, the layers being named the D, E, and F layers.</span></div><div><span style="font-family: arial;"><br /></span></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiEVGKh1M_ibkDIm5MVWoCMaycPKkq_qfYD6oCl507yKMwWYEKFF-GKgjkD95ps7QLgVKmFspWUIR0-640F2LCh5ENOnmrP3vkdBJSagbYsDdhk5LplGkgAi-9uzpMHqhenpMDS-ymvpkNHPpzuOsGTZxcLqA_ahxY9n5g40pWzCmUDN5a8K2YTinFiN8TI/s593/the_ionosphere.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="451" data-original-width="593" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiEVGKh1M_ibkDIm5MVWoCMaycPKkq_qfYD6oCl507yKMwWYEKFF-GKgjkD95ps7QLgVKmFspWUIR0-640F2LCh5ENOnmrP3vkdBJSagbYsDdhk5LplGkgAi-9uzpMHqhenpMDS-ymvpkNHPpzuOsGTZxcLqA_ahxY9n5g40pWzCmUDN5a8K2YTinFiN8TI/s16000/the_ionosphere.jpg" /></a></div><br /><span style="font-family: arial;"><br /><u><b>D-region 50-90 km (31-56 mi)</b></u><br /><br />The D-region is a region of low electron density whose degree of ionization is determined primarily by solar photoionization. This region usually exists during the daytime, and it absorbs the energy of MF radio waves that pass through it. The MF sky wave is therefore highly attenuated as it enters the D-layer during the daytime. At night in the absence of the photo-ionization created by the sunlight, the ionization in the D-region is at a much lower level or is nonexistent, so the D-region no longer absorbs the energy from the MF sky wave passing through it.<br /><br /><b><i>Daytime skywave.</i></b> Believe it or not, daytime skywave does exist and is present 24-7 in varying degrees depending on the season. In deep winter in the Northern Hemisphere (December, January), D-layer ionization during the day is strikingly less due to the lower solar position. Skywave signals, particularly at the upper end of the mediumwave band can pass right through it, and be reflected back to Earth off the E-layer at mid-day. Signals are weak, to be sure, but DX opportunities are abundant for those willing to dig for a signal. Deep winter D-layer absorption can be as much as 20-30 dB lower than at high summer (July, August).<br /><br />The effect can be striking and unexpected in low-noise areas of the country where you are free from the extreme RF density of the east. I used to spend winters in southwestern Arizona. My custom was to do an annual Christmas trip to Denver, Colorado and I'd set my car radio on a frequency of one of the extremely distant powerhouse stations. I have received KFI-640, Los Angeles, in Trinidad, Colorado at the noon hour, a distance of 800 miles. At peak, the signal hovered right at or barely above the noise level, with long deep fades. Now, that to me is exciting DX.<br /><br />Back at home in Arizona, I had a 25 ft. matched vertical, inductively-coupled to a variety of portable radios. Following is a sample of what was heard in deep winter during the middle part of the day.<br /><br /><u>Unusually good signals at noon:</u><br /><br />KSL-1160 Salt Lake City, UT (506 miles) never went away at the noon hours. Week but very readable from 11:00-13:00 local, then back up to very nice strength again by 13:30.<br /><br />KNBR-680 San Francisco, CA (524 miles)<br /><br />KALL-700 N. Salt Lake City, UT (515 miles)<br /><br />KCBS-740 San Francisco, CA (557 miles) with equal strength to two semi-locals KIDR-740 Phoenix and KBRT-740 Costa Mesa, CA.<br /><br />KZNS-1280 Salt Lake City, UT (512 miles) was booming in with an outstanding signal at 12:30 local.<br /><br /><u>By 13:00 local:</u><br /><br />KRVN-880 Lexington, NE appeared with decent strength. 944 miles.<br /><br />KLTT-670, 50 KW Commerce City, Colorado (681 miles, suburban Denver) under stronger 198 mile groundwave 25 KW KMZQ-670, Las Vegas, NV<br /><br />KNEU-1250 Roosevelt, UT at early afternoon. 515 miles but only a 5 KW station.<br /><br />KGAK-1330 Gallup, NM 339 miles (another 5 KW).<br /><br /><u><b>E-region 90-140 km (56-87 mi)</b></u><br /><br />During nighttime, the MF sky wave proceeds right on through the D-region to the E-region where it is refracted. The E-region ionization is from multiple sources that exist all of the time, so it is active during both the daytime and the nighttime. E-region ionization in the daytime is predominantly caused by solar ultraviolet and x-rays, while E-region ionization at night is caused predominantly by cosmic rays and meteors. The E-region is found at heights of 90 to 140 km, and it attains its maximum electron density near 100 km. This is the height within the E-region that is the predominant reflecting medium for MF propagation at night. The highly charged part of the E-region is a thin layer, roughly from 5 to 10 km (3 to 6 miles) thick.<br /><br />Seasonal E-layer heights, as measured by ionosonde are:<br /><br /></span></div></div></div><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px; text-align: left;"><div><div><div><span style="font-family: arial;"> Winter noon: 112 km, midnight: 118 km</span></div></div></div><div><div><div><span style="font-family: arial;"> Spring noon: 110 km, midnight: 108 km</span></div></div></div><div><div><div><span style="font-family: arial;"> Summer noon: 109 km, midnight: 104 km</span></div></div></div><div><div><div><span style="font-family: arial;"> Fall noon: 108 km, midnight: 111 km</span></div></div></div></blockquote><div><div><div><span style="font-family: arial;"><br />These are actually measured sporadic-E heights, intense clouds of ionization within the E-layer itself, however evidence suggests that the reflective part of the E-layer may extend all the way to 140-150 km above the Earth. Though MF skywave calculations almost always fix the reflection layer at 100 km, it is evident that reflection or refraction of the MF signal surely does occur at varying altitudes, much dependent on time of day, frequency, and a host of other variables.<br /><br />Critical frequency is a term used to describe the highest frequency above which radio waves penetrate the ionosphere and below which are reflected back. The critical frequency of the E-layer is mostly between 1.5 and 4 MHz, higher during a sunspot maximum than during a sunspot minimum.<br /><br />This tells us two things. If our critical frequency has dropped to 1500 kHz or even lower (1.5 MHz, stated above), our MF signal may transit through the E-layer and be reflected back to us off the F-layer. Second, we may see this effect more during periods of lower solar activity. The F-layer, at night, settles in at about 250-300 km altitude. This can result in single hop distances upwards of 3000 km (1864 mi). Look to the upper range of the mediumwave band to sometimes provide unusual DX, particularly in the late night and early morning hours before sunrise.<br /><br /><b>The skywave/groundwave mixture.</b> Skywaves and ground waves add vectorially. They can and do interfere with each other, the interference resulting in phase distortion in the audio you hear, and weakening (or strengthening) of the signal received at the receiver due to additive or subtractive combination. At night, at 500 kHz over average ground, the ground wave predominates over the skywave from the transmitter site out to distances of about 150 km, where the two signals are equal. The signals add as vectors, and destructive and constructive interference can occur. At 500 kHz at distances beyond 150 km, the sky wave is the predominant signal. At a signal frequency of 1500 kHz, the distance where the two signals are equal reduces to 45 km, because of the increased loss at the higher frequency.</span></div><div><span style="font-family: arial;"><br /><u><b>F-region 250-400 km (155-250 mi)</b></u><br /><br />The altitude of all the layers in the ionosphere vary considerably and the F-layer varies the most. During the daytime when radiation is being received from the sun, the F-region often splits into two: the lower and more insignificant one called the F1-region, and the higher and more significant one, the F2-region. Note also that the F1-region generally only exists in the summer. Typically the F1-layer is found at about an altitude of 300 km and the F2-layer at about 400 km.<br /><br />At night, the two regions combine, and the combined F-layer then centers around 250 to 300 km. Like the D and E layers the level of ionization of the F-region varies over the course of the day, falling at night as the radiation from the sun disappears. However the level of ionization remains much higher than the lower regions.<br /><br />The F-region is greatly affected by solar conditions. The maximum usable frequency, or MUF, is generally at least 15 MHz, but during the sunspot maximum period, the MUF may often exceed 50 MHz. The maximum usable frequency is the highest frequency that can be refracted off the ionosphere and returned to Earth (generally the F-region is implied).<br /><br />Then we have what is called lowest usable frequency, or LUF. The sky would appear to be the limit here, but the problem we have is our signal must first transit through the D and E layers to get to the F-layer. This probably </span><span style="font-family: arial;">isn't </span><span style="font-family: arial;">going to happen during the day in the mediumwave frequency range due to the highly absorptive D-layer. So, during the daylight hours, the D-layer will limit the lowest frequency allowed to pass through. At night, it's a different story.</span></div><div><span style="font-family: arial;"><br />As we said in our description of the E-region, almost all MF signals will refract off the E-layer at night. But under certain conditions and at certain times of year, when the critical frequency of the E-layer drops to 1500 kHz or below, we have F-layer skywave in the AM broadcast band, a fascinating phenomena.<br /><br /><u><b>Let's summarize.</b></u><br /><br />Practically, with all that said, our skywave prediction formula must choose a reflective layer height before we begin. The common choice is 100 km. Varied results will be found between 90 to 140 km, with the higher altitudes producing lower field strengths in general. The prediction experimenter might choose the higher altitudes for frequencies at the upper end of the mediumwave band, or they might even try forecasting for refraction off the F-layer at 250-300 km.<br /><br />In the next articles, we'll discuss Slant Distance and Geomagnetic latitude. We'll also talk more about ionospheric layer heights, and how they affect the two.</span></div></div><div><br /></div></div></div>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com0tag:blogger.com,1999:blog-4260200412608523752.post-60373222223337514882023-07-05T05:58:00.027-04:002023-07-14T06:43:32.021-04:00Mediumwave Skywave Prediction #2 - A Formula HistoryThe initial mediumwave measurement efforts of the 1930s resulted in graphs of expected field strengths, but only over certain tested paths. What was needed was a formula or formulas which would calculate strengths by plugging in actual transmitter and receiver locations. Scientists and engineers soon started work on this task. What they uncovered were yet more complications. The simple formulas they devised calculating path loss between two points, based on simple distance, didn't quite do it. There were other things going on high up in the ionosphere.<br /><br />Questions arose:<br /><br /><i>"Why do field strengths suffer if the signal path is anywhere near (within 5000 km, or about 3000 mi) the geomagnetic poles?"<br /><br />"How high is the reflective layer of the ionosphere for mediumwave at night? Does it vary?"<br /><br />"What about multiple hops? Is there an additional loss penalty there?"<br /><br />"Testing shows long paths over the sea result in increased strengths. Why is that?"<br /><br />"Does the solar cycle have anything to do with mediumwave skywave propagation?"</i><br /><br />And those weren't all.<br /><br />Some mysterious thing was also going on at the signal reflection point high in the ionosphere. There were losses there which couldn't be accounted for.<br /><br />Then there was the noticeable variability hour by hour throughout the day, every day. And certain peaks at the sunrise and sunset periods. Then someone noticed that signal strengths even varied by a few dB as the seasons progressed throughout the year.<br /><br />The engineers and scientists had a mess on their hands to try to sort out. World War II ended, and work continued in earnest to quantify all the new data being accumulated. New ideas came forth. Throughout the latter half of the 20th century, formulas were either tweaked or abandoned.<br /><br />The current plethera of formulas and tweaks available for mediumwave skywave field strength calculation is almost mind-boggling. Essentially, it all boils down to the overall path loss from transmitter to receiver. Once we have that, we can determine the expected received field strength. Luckily, we can attain high accuracy by breaking things down to basics, then tally the sum of the parts. The final path loss figure, in our familiar dB scale, is simply the addition and subtraction of the gains and losses of the individual pieces.<br /><br /><b>THE HEROES AND WHAT THEY FOUND</b><br /><br />K.A. Norton and John C.H. Wang of the FCC are 20th Century heroes of the first order. Almost singlehandedly they led the charge in the quest to calculate expected field strengths in the longwave and mediumwave regions. Norton led the early efforts, and Wang the later.<div><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEivBxqsnxioDzT2jMrQjwyK4c4vMViFztlXjyDJXEd2UohO2uvNS24ckqaT6dBSuLFh7i-xeYvoWtM287DkoPqvtiYrfmRc8TEyGacfrNVOq-ZARB-tw0USqoOH0XOcmagptPXAoHKNDkrbzbk2kC8ZErzfdx5MSJRFauqVU_X6PG0XF941sYbxDq_g0ksJ/s700/john_wang.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="700" data-original-width="465" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEivBxqsnxioDzT2jMrQjwyK4c4vMViFztlXjyDJXEd2UohO2uvNS24ckqaT6dBSuLFh7i-xeYvoWtM287DkoPqvtiYrfmRc8TEyGacfrNVOq-ZARB-tw0USqoOH0XOcmagptPXAoHKNDkrbzbk2kC8ZErzfdx5MSJRFauqVU_X6PG0XF941sYbxDq_g0ksJ/w213-h320/john_wang.jpg" width="213" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">John C.H. Wang 1934-2019</td></tr></tbody></table><br /><div>Let's talk about some of the formulas which emerged from all of this testing, and how they evolved. Or didn't!<br /><br />Over the last half of the 20th Century, several countries and the ITU (International Telecommunication Union) contributed greatly to the basic formulas we use for skywave field strength prediction. This was years in the making. Each region of the earth has different requirements. North America, for instance, has its close proximity to the geomagnetic pole to deal with. Polarization coupling loss (the loss as the signal transitions the reflection point in the ionosphere) is more of a problem in the tropics but not at high latitudes. East Asia and Oceania seemingly have greater propagational signal strengths than other areas of the world. One basic formula would not suffice for all regions. It wasn't until the millennium that the dust had finally settled and it became clear which formulas worked best for which region.<br /><br /><b>THE CAIRO CURVES</b><br /><br />The early Cairo curves of 1938 present field strength as a function of great circle distance only. The two Cairo curves and the FCC clear channel curve are similar for distances up to about 1400 km. At 3000 km the north-south curve is about 8 dB greater than the east-west curve. At 5000 km the difference is about 18 dB. The FCC clear channel curve falls between the two Cairo curves. The Cairo curves did not gain much recognition (in part, because of World War II) until 1975 when the LF/MF conference adopted the north-south curve for use in the Asian part of Region 3. The east-west curve, because it often underestimates field strength levels, has virtually been disregarded. The Cairo curves served their purpose well in the early years. Today it cannot be considered a candidate for worldwide applications.<br /><br /><b>THE OLD REGION 2 METHOD</b><br /><br />The old Region 2 method started out as the FCC clear channel curves. It has a long history dating back to 1935. It presents field strength as a function of great circle distance only. It does not take into account effects of other factors such as latitude, frequency, sunspot numbers, etc.<br /><br />North America has perhaps the most significant propagation anomalies to deal with. Increased positional geomagnetic loss (not auroral loss due to disturbed ionosphere) is strongest here in North America because of our closer proximity to the north geomagnetic pole than Europe at large. Wang, a long-time employee of the FCC, started to work on the skywave measurement problem by 1970. He soon was on the right track to a solution.<br /><br />Wang, in 1985 and again in 1989, reported that the old Region 2 method offers reasonable accuracy when applied to temperate latitudes, but when applied to low-latitude areas (e.g., Puerto Rico), it displays a tendency to underestimate. However, when applied to high-latitude areas (e.g., northern United States and Canada), it displays a strong tendency to overestimate. Wang stated, "Clearly, this is due to the fact that it lacks a treatment of latitude. The [old] Region 2 method has served its purposes well and cannot handle today's heavy demands for frequencies. It is not a candidate for worldwide applications."<br /><br />This antiquated method remained the recommendation of the ITU and the FCC for Region 2 well into the 1980s.<br /><br /><b>THE FCC METHOD</b><br /><br />John C.H. Wang, the star engineer of the FCC, had a heavy influence in developing the FCC formula. The modernized FCC method of the 1990s combines Wang's ideas on absorption losses and geomagnetic influence of the signal path's mid-point with the old Region 2 method and the original Cairo curves. Elsewhere, Wang contributed greatly to the world's scientific community by offering and publishing his personal ideas and formulas outside of the realm of the FCC. Wang's FCC contribution as well as his personal formulas include an additional loss factor of 4.95 dB to attempt to compensate for sunspot activity and the extra North American geo-polar proximity absorption. Neither the FCC's nor Wang's formulas account for frequency. Finally, where Wang adds a factor for the antenna's array gain over a standard quarterwave monopole, the FCC formula does not. The two methods produce, perhaps unsurprisingly, nearly identical results. <br /><br /><b>THE USSR METHOD</b><br /><br />The USSR method, authored by Udaltsov and Shlyuger and proposed in 1972, appeared to be very promising at first. For one thing, it included a sound treatment of latitudes. A previous study by Wang, et al., in 1993, using data collected in Region 1 only, had mixed comments about this method. The findings were as follows [Wang]: "(1) When applied to single-hop paths within Europe, reasonably accurate results have been obtained. (2) When applied to long paths terminating in Region 1, calculated results are typically 10 to 20 dB lower than the measured values. The current study (late 1990s), which uses a much larger data bank, has strengthened these findings. Furthermore, the frequency term in this method indicates that the higher the frequency is, the lower the field strength is. Although this is theoretically sound, measured data from Brazil, New Zealand, and the United States, however, does not corroborate this." Wang also suggested that it was something short of a true worldwide method. For a number of years this method was included in the ITU's reccomendation for worldwide application at frequencies between 150 and 1600 kHz.<br /><br /><b>THE ITU METHOD</b><br /><br />The 1974-1975 ITU Geneva conference adopted the USSR method for official use in Region 1 and in the southern part of Region 3 with modifications. P. Knight's 1975 sea gain formula and the J.G. Phillips-Knight 1965 polarization coupling loss term were also included. The ITU has adapted and modified this formula for general worldwide use to this day. It has some shortcomings for North America, as we will soon see.<br /><br />The ITU method makes predictions that depend on both frequency and geomagnetic latitude. The field strength values are not symmetrical about the geomagnetic latitude equal to 0 degrees. The field strength expression also predicts lower field strength values as the frequency is increased in the MF band, but measurements performed in the United States show that the field strengths are higher at the higher frequencies in the MF band when compared to those measurements at the lower frequencies. Because of this discrepancy, the ITU method has not found wide acceptance as a worldwide prediction method. Curiously, their bandaid-approach is recommending a fixed frequency of 1000 kHz to represent the entire MF band.<br /><br /><b>THE WANG METHOD (1999)</b><br /><br />The brilliant engineer John C.H. Wang started with the FCC in about 1970, and stayed for 40 years, continuing K.A. Norton's early work. Wang had made tremendous inroads by 1977, and after examining all of the available MF methods, developed a new MF skywave field strength prediction method for North America. Like the Udaltsov and Shlyuger method, the Wang method also contains a latitude term. The original FCC curves have a hump at roughly 100 km which Wang concluded was due to groundwave interference present in the 1935 data. The curves become smoother and better behaved after removal of these data points. Furthermore, this new method essentially linked the Cairo and the FCC clear channel curves together mathematically. The special case corresponding to a geomagnetic latitude of 35 degrees north in the Wang method is extremely close to the Cairo curve; the difference is within a fraction of a decibel. The special case corresponding to 45 degrees north is very similar to the old FCC curve. More importantly, it works well for long and short paths alike. Wang further improved on this method in 1979, modifying the ITU's basic loss factor (Kr) for North America and also tweaking the solar activity dependence factor (bsa). The formula was further tweaked again and published in 1985.<br /><br />In 1986 the Region 2 conference which tackled the expanded band adopted Wang's method for calculating interregional interference. In 1990 this method became part of the FCC rules and regulations replacing the old clear channel curves (actually, the old Region 2 method) for domestic applications. In 1994 this method was adopted by the ITU for calculating field strengths between 1600 and 1700 kHz. This method has several other convenient features that should not be overlooked. It is simple and easy to use; a handheld calculator would suffice. The calculation procedures and required input information are similar to the Udaltsov and Shlyuger method, the method being used by Region 1 countries. Wang continued with improvements throughout the rest of the 1980s and into the millennium.<br /><br /><b>OTHER METHODS</b><br /><br />There are other prediction methods, some obscure or archaic. Namely, these are: the Norton Method (1965), the EBU Method (1962, reaching its final form in 1978), the Barghausen Method (1966), the E. Oliver Method (1971), and the P. Knight Method (1973). The Knight's method eventually was simplified, evolving into the UK Method.<br /><br />The Cairo curves, the Norton, the EBU, and original ITU-sanctioned 1974 USSR methods still used actual overland great circle distances in their formulas. The modified USSR method (1978) uses the slant distance. Wang of the FCC was using slant distance by 1977.</div><div><br /></div><div>In the next article we'll introduce the formulas.<br /><div><br /></div></div>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com0tag:blogger.com,1999:blog-4260200412608523752.post-8670911541635324822023-07-02T07:27:00.093-04:002023-07-05T07:17:57.955-04:00Mediumwave Skywave Prediction #1 - A Measurement History<p>Skywave propagation at mediumwave is a fascinating subject, both from a historical and technical standpoint. Radio itself has been around well more than 100 years, and broadcast radio since about 1920. As more and more stations entered the airwaves, nighttime spectral chaos ensued. How was it all sorted out? Who took charge of all this? How did we arrive at the calculations necessary to ensure that the thousands of radio stations transmitting didn't interfere with each other? What exactly goes into calculating a nighttime skywave signal strength for a distant medium wave station?</p><p>Let's try to answer these questions in this series. We'll cover the history in the first couple of articles, then dive into the technical in subsequent articles. Throughout this series, the LF and MF abbreviations, when used, refer to the longwave frequency (LF) and mediumwave frequency (MF) bands. Note that these articles discuss mediumwave skywave prediction only.</p><p><b>THE LEAD-UP</b></p><p>At the end of World War I, a fierce battle ensued between the US government and the Department of the Navy over control of the airwaves. The Department of Commerce eventually won and became master of the air and the regulatory agency for commercial radio here in the US. They started by establishing two broadcast frequencies: 833 kHz (360 meters) and 619 kHz (485 meters). The Federal Radio Commission took charge in 1926, lasting until 1934 when the current Federal Communications Commission was formed. By 1930, broadcast radio was on its way. Nighttime signals traversed the continent from coast to coast.</p><p>Throughout the early years of radio, interest mounted to quantitatively determine the service area of broadcast stations. Early mathematical efforts focused mainly on finding an accurate calculation for groundwave coverage. K.A. Norton of the FCC would play a major role worldwide in that effort. The intricacies of skywave would be unveiled later. You might be surprised to know that serious study of longwave and mediumwave skywave propagation didn't commence until some 12 years after the first commercial AM radio station went on the air.</p><p><b>EARLY MEASUREMENT EFFORTS</b></p><p>The earliest worldwide concerted efforts to study longwave and mediumwave skywave propagation began in 1932. The International Radio Consultative Committee (CCIR), an arm of the ITU, formed a task force in that year to study propagation at frequencies between 150 and 2000 kHz. Three measurement campaigns were carried out between 1934 and 1937 on 23 long-range propagation paths between North America and Europe, North America and South America, and Europe and South America. Measurements on 10 short paths within South America were also carried out under the administration of Argentina. Two skywave propagation curves (skywave field strength graphs ordered by frequency and distance) were drawn based on the results of these measurements. One of the curves is for paths far away from Earth’s magnetic poles (north-south curve), while the other curve is for paths which approach Earth’s magnetic poles (east-west curve). The two curves were formally adopted at the 1938 International Radio Conference in Cairo and are known as the Cairo curves. They have survived, with modification in one form or another, to this day.</p><p>Click any image for the bigger picture.</p><p><br /></p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkQfzI8ldMGuuocGyBNgLN8fC0u61Ei2N42QI4Vb1lVWC1LWs7SD3noUz0NP1WA4hwufudF-AVM2NfO5s59FLP3WN3MUAsouM9UApkm9VcfstyCiVefcUlLdA2Y72-PXJGtTk3G9VnixYj4coQGvkIFCAcLoioiv2Bj3x8xINMrmX7mcksrN9DlXWuyDWL/s936/cairo-curve-map.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="936" data-original-width="774" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkQfzI8ldMGuuocGyBNgLN8fC0u61Ei2N42QI4Vb1lVWC1LWs7SD3noUz0NP1WA4hwufudF-AVM2NfO5s59FLP3WN3MUAsouM9UApkm9VcfstyCiVefcUlLdA2Y72-PXJGtTk3G9VnixYj4coQGvkIFCAcLoioiv2Bj3x8xINMrmX7mcksrN9DlXWuyDWL/w530-h640/cairo-curve-map.jpg" width="530" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">The Cairo Curve Measurement Campaign</td></tr></tbody></table><br /><div><br /></div><div>The Federal Communications Commission (FCC) of the United States carried out a skywave field strength measurement program in the spring of 1935 to derive a new set of curves for North America. At that time, there were eight clear channel stations. Nighttime signals of these stations were monitored at 11 receiving sites located in different parts of the United States. The curve corresponding to the annual median value (the signal level expected to be exceeded at least 50% of the time) was used to determine a station's coverage area, while the curve corresponding to the upper decile value (the signal level expected to be exceeded at least 10% of the time) was used to calculate the interference levels among co-channel stations. Characteristically, the 10% level is the higher signal level. These curves became part of the rules and regulations of the FCC and were adopted by the 1950 North American Regional Broadcasting Agreement (NARBA) for official use in the North American Region, which comprised the following areas: Bahama Islands, Canada, Cuba, Dominican Republic, Haiti, Jamaica, Mexico, and the United States. This method was eventually adopted with minor modifications for applications in all of ITU Region 2. It would not survive the millennium.</div><p>The FCC, knowing the clear channel curves had certain limitations (the curves do not take into consideration the effect of latitude and the proximity to the geomagnetic pole), initiated a long-term large-scale measurement program in 1939 to collect measurements from more than 40 propagation paths. The measurement program lasted for about one full sunspot cycle; in four cases it lasted for two cycles and ended in 1958. Frequencies of these paths ranged from 540 to 1530 kHz. Path lengths ranged from 322 to 4176 km. Mid-point geomagnetic latitudes (the signal reflection point between transmitter and receiver relative to geomagnetic north) ranged from 45 degrees to 56 degrees north, a narrow range of 11 degrees, although some paths from lower latitudes were later added. More about geomagnetic latitude later in the series.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjo_-P9H0PXGrmnoXPwnPQ-4sk5LG6_Mhtr1f-9F5P5oY-R9c55DhR-SIX0x5_UUQOi_WXAmyvt8qDfVwRbCQ7v-iSyttrVtZkKYvW6onHaKaAAiCivwJ9eIRzDI3U08y9TJKccnKnW2nUmtSJrt7uTu8mSSW2ByfPgFtxK4lDeXp08dGVh6d8jh9IpPcLJ/s98/ITU_logo.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="94" data-original-width="98" height="94" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjo_-P9H0PXGrmnoXPwnPQ-4sk5LG6_Mhtr1f-9F5P5oY-R9c55DhR-SIX0x5_UUQOi_WXAmyvt8qDfVwRbCQ7v-iSyttrVtZkKYvW6onHaKaAAiCivwJ9eIRzDI3U08y9TJKccnKnW2nUmtSJrt7uTu8mSSW2ByfPgFtxK4lDeXp08dGVh6d8jh9IpPcLJ/s1600/ITU_logo.jpg" width="98" /></a></div><p><b>THE ITU</b></p><p>I'll side-track for a minute and tell you about the ITU, the International Telecommunication Union, and how regions are defined. Today the ITU is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on May 7, 1865 as the International Telegraph Union, making it the first international organization. The ITU has divided up the planet into three regions. Region 1 comprises Europe, Africa, the entire former USSR, Mongolia, and the Middle East west of the Persian Gulf, including Turkey and Iraq. Region 3 contains most of non-former USSR, Asia east of and including Iran, and most of Australasia. Region 2 covers the Americas including Greenland, and some of the eastern Pacific Islands.</p><p><b>MID-CENTURY EFFORTS</b></p><p>Back to our history.</p><p>The Canadian Department of Transportation took path measurements in 1947, a year of maximum sunspot number and minimum field strengths.</p><p>The EBU, the European Broadcasting Union, carried out an extensive measurement campaign from from 1952 to 1960 for paths in western Europe. A controversial field strength prediction method was developed by Ebert in 1962. In this method, empirical relationships were derived for the effects of solar activity, the influence of magnetic field, frequency, and other factors. The Ebert method cannot be considered a success because it displayed a strong tendency to grossly underestimate field strength levels, sometimes by 30 dB. It was soon abandoned. Although the Ebert method was not a success, the importance of the EBU measurements cannot be overlooked. </p><p>Three international organizations, the EBU among them, in 1963 and 1964 set up 7 receiving locations on the continent of Africa and did studies of propagation paths from two transmitters on Ascension Island. One phase of the project was to study polarization coupling loss and sea gain. Germany also conducted measurements at Tsumeb, southwest Africa. Altogether, the African measurement campaign involved 15 receiving sites, and data from 33 paths was documented. Frequencies ranged from 164 kHz to 1484 kHz. Distances ranged from 550 km to 7540 km. Mid-point geomagnetic latitudes ranged from 29 degrees south to 40.2 degrees north. Of these 33 paths, three were from Europe to Africa.</p><p>In the late 1960s and early 1970s a number of administrations and scientific organizations made valuable contributions. The EBU reactivated its efforts and collected data from more than 30 propagation paths; many of these are intercontinental paths. In Eastern Europe, the International Organization of Radio and Television (OIRT) contributed data from 12 short intra-European paths between 600 and 1400 km at frequencies between 164 and 1554 kHz. The former USSR also collected a significant amount of measurements. A summary of their results and a proposed new calculation method was published in 1972.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgy8plON2U82CG1d8un9luAtSHReubw9JJO6bdX8mV6RoJ2MiPiRyJRUkqv3ZkMnceZEWmYxpWuAFLlzsnMsoG85urYSdHVa7U5wyxFMlee01YIDHyks2818TRjsGpvnnYcgh_jrWM3LYdOwzwOlVw9L4gtshrXone7k1C1QqjJUGOp32v6TUd-p2LpOh8z/s574/ITU-geneva-1975.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="574" data-original-width="406" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgy8plON2U82CG1d8un9luAtSHReubw9JJO6bdX8mV6RoJ2MiPiRyJRUkqv3ZkMnceZEWmYxpWuAFLlzsnMsoG85urYSdHVa7U5wyxFMlee01YIDHyks2818TRjsGpvnnYcgh_jrWM3LYdOwzwOlVw9L4gtshrXone7k1C1QqjJUGOp32v6TUd-p2LpOh8z/w226-h320/ITU-geneva-1975.jpg" width="226" /></a></div><br /><p><b>THE 1974-1975 ITU GENEVA REGULATORY CONFERENCE</b></p><p>The big one, perhaps the biggest ever. The ITU's Regional Administrative LF/MF Broadcasting Conferences were held in Geneva, Switzerland for Regions 1 and 3. This was a major deal on several fronts. Channel spacing was to be decided on, worldwide. It was 1975!!! Also signal strength calculation standards were to be fixed and tailored by region and sub-region. Asian countries, particularly China, preferred the Cairo north-south curves. Australia and New Zealand believed neither method was adequate for their applications. They believed field strength levels in their part of the world are stronger than those observed in other places. Finally, a compromise was reached.</p><p>It was decided that the USSR method was to be used for Region 1. The Cairo north-south curve was to be used for the northern part of Region 3 (east Asia). For the southern part of Region 3 (Oceania) the modified USSR method was to be used with a correction factor of 2.7 dB added to the basic formula. Sea gain and polarization coupling loss terms were to be included whenever applicable. The propagation issue was a lesser concern compared to the channel-spacing issue. The conference was deadlocked for a number of weeks over two separate proposals: 8 kHz versus the traditional 10 kHz separation. Finally, a compromise of 9 kHz was adopted which became effective in November of 1978 for Regions 1 and 3.</p><p>In the meantime, the interference situation in South America was going from bad to worse, mainly because of the lack of any regional agreement, although some bilateral agreements were in existence. The situation in North America was somewhat better, thanks in part to the 1950 NARBA agreement.</p><p>After the ITU's LF/MF conference for Regions 1 and 3 was over, a number of administrations in South America petitioned the ITU to convene a regional conference involving all countries in ITU Region 2, the Americas. Consequently, two sessions took place. The first session dealt with technical matters and took place in 1980 in Buenos Aires. The second session dealt with the actual planning and took place in 1981 in Rio de Janeiro. The FCC clear channel curve was adopted for use in the entire region. It was also decided that sea gain and polarization coupling loss terms were not to be included in the calculations. At the first session, channel spacing was a very hot topic. The United States was in favor of 9 kHz (for all of South America), while Argentina and Canada were strongly against it. At the second session, the United States withdrew its proposal, and 10 kHz spacing was quickly agreed upon. It should be mentioned that in Region 2, longwave is not used for broadcasting. Therefore the 1980-1981 conference dealt with mediumwave only (535 kHz to 1605 kHz).</p><p><b>ONWARD TO THE MILLENNIUM</b></p><p>The CCIR Documents of the 1978 Kyoto Assembly further modified the 1974 sky-wave field strength prediction method for MF (150 to 1600 kHz) and recommended its provisional use worldwide. Several sky-wave field strength prediction methods proposed for various parts of the world also were described. </p><p>They are:</p><blockquote style="border: none; margin: 0px 0px 0px 40px; padding: 0px; text-align: left;"><p>1) Cairo North-South curve adopted for use in Asian part of Region 3 - mathematical approximation presented.</p><p>2) EBU method to be used in European Broadcasting Area with separate formula for distances less than 300 km.</p><p>3) USSR method - valid between 37° and 60° geomagnetic latitude for distances up to 6000 km and has no frequency dependence.</p><p>4) UK method - valid for all distances worldwide except for the auroral zones and has no frequency dependence.</p><p>5) Region 2 would use the FCC's method. The Wang 1977 method (Wang was a newly-hired and brilliant engineer at the FCC) was given as an alternative method for use in Region 2.</p></blockquote><p>In 1979 Wang proposed a modification of the CCIR Kyoto 1978 worldwide method to improve accuracy in Region 2. Also in the same year, the Inter-American Conference on Telecommunications extended the FCC median signal level curve to distances beyond 4300 km using the Cairo North-South Curve and recommended its adoption for Region 2.</p><p>In response to Region 2 countries' request for more frequencies for broadcasting, the 1979 World Administrative Radio Conference (WARC-79, held in Geneva) of the ITU allocated the band 1605-1705 kHz for broadcasting in Region 2 only. Two sessions of regional conference took place in 1986 (Geneva) and 1988 (Rio de Janeiro) for the planning of the use of this expanded band in Region 2. It should be noted that this band is used by other services in Regions 1 and 3.</p><p>In preparation for the use of the expanded band and recognizing the need for additional data, particularly data from low and high latitude areas, the FCC initiated two separate projects in the early 1980s. In 1980, the FCC and the Institute for Telecommunication Sciences (ITS) of the Department of Commerce jointly began to collect low-latitude data at two receiving sites: Kingsville, Texas, and Cabo Rojo, Puerto Rico. The FCC-ITS efforts in low-latitude areas were supplemented by Brazil and Mexico; both administrations also collected a significant amount of data from low-latitude areas. In 1981, the FCC started a joint project with the Geophysical Institute, University of Alaska. The Alaskan project concentrated on high latitude data and lasted for five years, collecting data representing different levels of solar activity.</p><p>Administrations in the Region 3 area, Australasia, in cooperation with the Asian-Pacific Broadcasting Union, were equally active and productive in their path testing. In the northern part of this region, data from 84 paths had been documented by 1981. Australia and New Zealand jointly collected data from 85 paths. The Japanese administration had carried out a series of mobile experiments in the Pacific by 1987.</p><p>By the year 2000, measurements from more than 400 propagation paths had been documented. Great circle lengths of these paths ranged from 290 to 11,890 km. Signals of the few very short paths were verified to be skywaves. Frequencies ranged from 164 kHz to 1610 kHz. Control-point geomagnetic latitudes ranged from 46.2 south to 63.8 north geomagnetic latitude. A large amount of literature had been generated. By this time, largely the work of the ITU in setting standards and regulations for the longwave and mediumwave bands was finished. Fine tuning of the skywave calculation formulas was left to the scientists.</p><p>In the next part of this series, we'll wrap up the history and then go on to explore elementary skywave prediction and what is involved in solving it.</p><p><br /></p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiy1En9ast1eFp4y8qBAE4ciPsUaQ2OD7U7DrEv9Zmr_GQ1nadCjA_gWcs2hpArq23SR5WdB2jqigNL-Eh14I-g-XZ7KkpvGANznluw7lNzopfE_FdYE5j-R6MQmBpbz8GLKKy5rMoaXKfOdaQHLevvr28sWInskojnVRxCRmvZfb3KI3l0IL08nEEEVmVB/s1200/International_Telecommunication_Union_regions_with_dividing_lines.svg.png" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="609" data-original-width="1200" height="203" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiy1En9ast1eFp4y8qBAE4ciPsUaQ2OD7U7DrEv9Zmr_GQ1nadCjA_gWcs2hpArq23SR5WdB2jqigNL-Eh14I-g-XZ7KkpvGANznluw7lNzopfE_FdYE5j-R6MQmBpbz8GLKKy5rMoaXKfOdaQHLevvr28sWInskojnVRxCRmvZfb3KI3l0IL08nEEEVmVB/w400-h203/International_Telecommunication_Union_regions_with_dividing_lines.svg.png" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">ITU Regions</td></tr></tbody></table><p><br /></p><p></p>
<pre style="font-family: Arial; font-size: small;">Information for these articles has been gathered from the following resources:
An Objective Evaluation of Available LF/MF Skywave Propagation Models
John C.H. Wang
Radio Science, Volume 34, Number 3
May-June 1999
NTIA Report 99-368
Medium Frequency Propagation Prediction Techniques and Antenna Modeling
for Intelligent Transportation Systems (ITS) Broadcast Applications
Nicholas DeMinco
US DEPARTMENT OF COMMERCE
August 1999
International Telecommunication Union Handbook
The Ionosphere and its Effects on Radiowave Propagation
Radio Communication Bureau 1998
Code of Federal Regulations Title 47
Radio Broadcast Services (FCC)
47 CFR Part 73
FCC Standard AM Broadcast Technical Standards
...notes and changes to 47 CFR Part 73
Broadcast Service Bureau
Filed January 20, 1987
Medium Frequency Propagation: a survey
P. Knight
BBC Research Department 1983/5
May 1983
NTIA-Report-80-42
Comparison of Available Methods for Predicting Medium Frequency
Sky-Wave Field Strengths
Margo PoKempner
US DEPARTMENT OF COMMERCE
June 1980
LF AND MF SKY-WAVE PROPAGATION: the origin of the Cairo curves
P. Knight
BBC Research Department 1977/42
November 1977
</pre>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com1tag:blogger.com,1999:blog-4260200412608523752.post-68055039773948873592023-06-09T09:34:00.012-04:002023-06-09T09:40:13.891-04:00The Fascinating Beverage Antenna Patent<p><i>April 8, 1920</i></p><p><i>"To all whom it may concern:"</i></p><p><i>"Be it known that I, HAROLD. H. BEVERAGE, a citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Radio Receiving Systems, of which the following is a specification.</i></p><p><i>My present invention relates to radio receiving systems and more particularly to an improved arrangement of an antenna for receiving purposes.</i></p><p><i>The object of my invention is to provide a receiving antenna which will have highly directive properties, which will be very efficient in its operation and which will also be highly selective.</i></p><p><i>In carrying my invention into effect I make use of a horizontal preferably aperiodic antenna extending in a direction parallel to the direction of transmission of the signals to be received.</i></p><p><i>This antenna is constructed with distributed capacity inductance and resistance of Such values that the currents produced therein by the desired signals increase progressively from the end of the antenna nearest the transmitting station be coming in the preferred case, the maximum at the end farthest from the transmitting station."</i></p><p>Thus starts the patent application of one Harold H. Beverage for his famous "Beverage" antenna. Filed with the U.S. Patent Office, April 8, 1920. Approved June 7, 1921. Patent #1381089. Just imagine, radio was in its infancy in 1920 and along comes this marvelous antenna, the Beverage.</p><p>The Beverage antenna, patented by Harold H. Beverage, is a type of longwire antenna used for radio communication, specifically receiving. It is named after its inventor and is known for its simplicity and effectiveness in receiving weak signals. The antenna consists of a single wire, usually several wavelengths long, which is suspended a short distance above the ground.</p><p>The Beverage antenna is typically oriented in a specific direction to optimize its reception capabilities. It is commonly used for receiving high-frequency signals, such as those in the shortwave and mediumwave bands. The long length of the wire allows for enhanced directivity and low-angle radiation, which makes it particularly suitable for long-distance communications.</p><p>One of the main advantages of the Beverage antenna is its ability to reduce noise and interference from unwanted directions. By carefully selecting the orientation and placement of the wire, it is possible to maximize signal reception from the desired direction while minimizing signals coming from other directions. This makes the Beverage antenna valuable for receiving weak or distant signals in environments with high levels of electromagnetic interference.</p><p>Harold H. Beverage patented the design of this antenna in the year 1920-21, and it has been widely used by radio enthusiasts, amateur radio operators, and professionals ever since. The Beverage antenna remains a popular choice for those seeking long-range reception and reliable signal quality. Just below, have a look at the original H.H. Beverage patent filing. It makes for interesting reading.</p><p>Click on any to enlarge.</p><div class="separator" style="clear: both; text-align: center;"><br /></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmcFp14Lie7DrOlN8D02WIdlmtUB0isKz2RoTAVWXGJk5D_2PoGUlQp4K3QuYNjAuelJd17tDOL5Lvk8OKB5tdwPWDN-SP9R-rJQt6K8Whfmi2ayT8Yv_rwCUx3o6uXHGRnaxHnACxcNNPCkz8_J59toXWRB1S6ZKORNIxd7AcA2YaaDoR87JN_YMA1Q/s1024/Beverage%20Patent_US13810891024_1.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1024" data-original-width="696" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmcFp14Lie7DrOlN8D02WIdlmtUB0isKz2RoTAVWXGJk5D_2PoGUlQp4K3QuYNjAuelJd17tDOL5Lvk8OKB5tdwPWDN-SP9R-rJQt6K8Whfmi2ayT8Yv_rwCUx3o6uXHGRnaxHnACxcNNPCkz8_J59toXWRB1S6ZKORNIxd7AcA2YaaDoR87JN_YMA1Q/w436-h640/Beverage%20Patent_US13810891024_1.jpg" width="436" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhk4kaZazZoXYEMOKUU-e0q7-8J3Oq2aRvNQ61dSoiyjMsIfzvrzQGxmF75YerstkqhC-4EYZRflSzxrCcm1hvJ-lbBug3CNhGP9ph3BflhAkvjvm3A6Zf25abau7_8BxtffPUOBzZQ1R3qdQkpMJErr6G7j27U5EKf5kzzBfaAaQqlMorkeZPXri65-Q/s1024/Beverage%20Patent_US13810891024_2.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1024" data-original-width="696" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhk4kaZazZoXYEMOKUU-e0q7-8J3Oq2aRvNQ61dSoiyjMsIfzvrzQGxmF75YerstkqhC-4EYZRflSzxrCcm1hvJ-lbBug3CNhGP9ph3BflhAkvjvm3A6Zf25abau7_8BxtffPUOBzZQ1R3qdQkpMJErr6G7j27U5EKf5kzzBfaAaQqlMorkeZPXri65-Q/w436-h640/Beverage%20Patent_US13810891024_2.jpg" width="436" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjupWdnZb8vQ4C6G0cxIYVnBdMaZQ3R3cEp4IQjeVvcRaSLgdr5sLPabRTGGNsWIFPxYT87m4Pk3e0HtFZ_ni1U12wl4h10cq5uaPds-IP7RgSvjXbJyoCMJHzRXbcrRiTcN_m_AwF4j6H58_tb8Ia5YtNjRId_LJ7wf09MnPTggXE03UGHSUF0nXgpvA/s1024/Beverage%20Patent_US13810891024_3.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1024" data-original-width="696" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjupWdnZb8vQ4C6G0cxIYVnBdMaZQ3R3cEp4IQjeVvcRaSLgdr5sLPabRTGGNsWIFPxYT87m4Pk3e0HtFZ_ni1U12wl4h10cq5uaPds-IP7RgSvjXbJyoCMJHzRXbcrRiTcN_m_AwF4j6H58_tb8Ia5YtNjRId_LJ7wf09MnPTggXE03UGHSUF0nXgpvA/w436-h640/Beverage%20Patent_US13810891024_3.jpg" width="436" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhe0zr2uiAMoGToIxIPWdVyjl9cL6-t3Os2ebKtA6pNM3eQHBRS5DgA_fzxW9A6lmUSEkFq-BlLN4m8Cczp7pOkUVCG_EMaf8fRHqxFR2vOjoR3pdseMrK-xIibbMIS9WK53DtmdeEiy6A4HTI7hSe5s-p-Od1sWJXj7zpwpHOQF7ti5mHY9vi7LwyuRA/s1024/Beverage%20Patent_US13810891024_4.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1024" data-original-width="696" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhe0zr2uiAMoGToIxIPWdVyjl9cL6-t3Os2ebKtA6pNM3eQHBRS5DgA_fzxW9A6lmUSEkFq-BlLN4m8Cczp7pOkUVCG_EMaf8fRHqxFR2vOjoR3pdseMrK-xIibbMIS9WK53DtmdeEiy6A4HTI7hSe5s-p-Od1sWJXj7zpwpHOQF7ti5mHY9vi7LwyuRA/w436-h640/Beverage%20Patent_US13810891024_4.jpg" width="436" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEihu5ferXsLzqBQpSOw3uABmI5ahJZ_TGC9HvvFBFiLWXyFQu5mvSK3B4w-bN7gTvld0t0ky2pi9KorFPSYwqgiiUj4RTs1UVYs3xnq--znyJtrzjwdULNlxsOkaBOuHfcYe2IlSnFlCbDjUSUuo_HgWKRs5Int2II3FuzqP4I7ouEfshMhSROustIwuw/s1024/Beverage%20Patent_US13810891024_5.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1024" data-original-width="696" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEihu5ferXsLzqBQpSOw3uABmI5ahJZ_TGC9HvvFBFiLWXyFQu5mvSK3B4w-bN7gTvld0t0ky2pi9KorFPSYwqgiiUj4RTs1UVYs3xnq--znyJtrzjwdULNlxsOkaBOuHfcYe2IlSnFlCbDjUSUuo_HgWKRs5Int2II3FuzqP4I7ouEfshMhSROustIwuw/w436-h640/Beverage%20Patent_US13810891024_5.jpg" width="436" /></a></div><br /><p><br /></p>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com2tag:blogger.com,1999:blog-4260200412608523752.post-25532623542294247512023-05-18T10:32:00.000-04:002023-05-18T10:32:22.562-04:00A Review Of The XHData D-109 DSP Radio<p>Next up, let's talk about the new XHData D-109 DSP radio. I ordered one from Amazon last week and it came over the weekend. It was just over $30 with free shipping from XHData using Amazon Prime.</p><p>The D-109 is a beautiful little radio, slightly larger in height and width than XHData's analog DSP radio, the D-219. It measures out at 6 inches wide, 3-1/4 inches high, and 1-1/4 inches thick. It is quite a bit larger than the RadiWow R-108.</p><p><br /></p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi0YL98R3HZcfh3ucC1GJBtajZrT04gr72ei-dgQCUlvsPU6rBnCr5x5xWpzzwg0bwNC6O7IK63l4UlXW7vqVg2XUSK7wIkXjI9gl_ZkFLYv2JHI3X8cvI4R4eDwTElTHJfv-ZkXN3kSxIJe6vd9xOabomViWuGgt9DzlvllfBF-oZyqsiz4RV78ZqrLA/s1024/D-109-1.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="626" data-original-width="1024" height="245" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi0YL98R3HZcfh3ucC1GJBtajZrT04gr72ei-dgQCUlvsPU6rBnCr5x5xWpzzwg0bwNC6O7IK63l4UlXW7vqVg2XUSK7wIkXjI9gl_ZkFLYv2JHI3X8cvI4R4eDwTElTHJfv-ZkXN3kSxIJe6vd9xOabomViWuGgt9DzlvllfBF-oZyqsiz4RV78ZqrLA/w400-h245/D-109-1.jpg" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">XHData D-109</td></tr></tbody></table><br /><p>Full coverage of mediumwave is available - 520 to 1710 kHz. All AM bandwidths are available - 1,2,3,4,6 kHz. It tunes in 1 kHz steps. The radio also covers the longwave band. It came pre-activated on my radio, but may be disabled if you wish. Shortwave coverage is complete, from 1711 kHz to 29999 kHz. FM coverage ranges from 64 to 108 mHz, seemingly all in one band.</p><p>Fit and finish is good. The sound from the front-facing speaker is very pleasant, as others have stated. Two watts of audio are available. It has impressive battery life with the lithium 18650, 2000 mAh battery. I've been running it using the speaker for several hours per day for nearly a week, and the battery still shows a full charge. Charging is through a typical USB cable plugged to a 5 volt source. The XHData designers have used a USB-C style connector, a bonus.</p><p>I found the tuning knob is a little small, but adequate. Frequency entry on the keypad is direct and immediate, like the Tecsuns have, nice. No extra buttons to press. Keys are robust and click with a tactile snap, and feel like they'd last a long time. The display is backlit with a nice soft golden yellow color. The display is crisp and clear, but otherwise typical for a digital DSP radio. It shows battery charge, clock time, alarm times, temperature, and receive RSSI (in the typical dBµV) and SNR (signal-to-noise) levels.</p><p>The radio has a clock, two alarms, and a sleep function. A scan function scans any band of interest quite nicely. Plenty of memories are available for those who use them. 100 each for FM, longwave, and mediumwave, 300 for shortwave.</p><p>The radio supports bluetooth and can be used to play audio from an external device through its bluetooth connection. It also sports a TF card slot for a micro SD card, which can be loaded with music and played through the radio's audio system. Allowed formats are: MP3, WMA, WAV, and FLAC. Recording of received station's audio is not possible, unfortunately. At least as far as I can tell.</p><p>For mediumwave, the 10/9 kHz channel step choice is easily set by holding down the 2 key for a couple of seconds when the radio is off. Tuning is interesting. The radio seems to be locked at a 1 kHz tuning rate (10 kHz for FM) unless you rotate the tuning dial quickly, which then goes into fast tune and steps at 10 (or 9) kHz (mediumwave) or 5 kHz (shortwave) or 100 kHz (FM). For example, on mediumwave, tuning slowly tunes as such... the frequency changes: 620..621..622..623..624..625..jump to 630. They've elected to advance to the next channel when you pass the 5 kHz halfway point. There are channel up/down buttons too. The channel up/down buttons only step up or down 1 kHz at a time, and no convenient channel jump at the 5 kHz halfway point. I feel it would have been better for channel up/down to advance at the user's chosen 9 or 10 kHz step and not 1 kHz. Maybe someone has figured out something which circumvents this.</p><p>Mediumwave sensitivity is exceptional. I did some signal strength comparisons with the R-108 and it is identical, or better. Even the RSSI (dBµV) readings are within one or two dB. It is more sensitive than my larger old school analog Tecsun R-9700DX, slightly better than my D-219 DSP analog, way better than my Sangean SR-35 and Dreamsky DSP analogs. In fact, it holds its own against my PL-880 and Sangean ATS-909X. That's impressive. Now comes the problem.</p><p>Shortwave is the problem. Maybe not a fair test here, as I am within 1.5 miles of two 5000 watt stations. I am bathed in more than 200 mV/m from each of those stations, 266 mV/m from one. Those are truly clobbering signals, 1/4 of a volt per meter. My SDRs can barely handle it. Intermod and overload on shortwave coming from the mediumwave band, particularly between 2-8 mHz, basically makes shortwave unusable for me at this location. An initial trial in the country about 4.5 miles from a 20 KW transmitter had a similar negative result. I need to take this radio well out into the country, far from mediumwave transmitters, and see if that makes a difference.</p><p>I was convinced I could remedy this but could not. I plugged in an external antenna, running the coax feed through a 30 dB (attenuation) RTL-SDR broadcast AM Reject filter in series with an old Grove TUN-4 preselector for the shortwave bands. It did not work, in fact it was worse. Experimenting with a shorted piece of coax with no antenna connected, I discovered that part of the problem is that mediumwave signals are somehow being funneled into the radio via the antenna ground (the coax shield). The longer the shorted piece of coax got, the worse was the intermod. More experimenting is yet to come. Shortwave above 41 meters is a little better, but still hit and miss, though when I was able to null the mediumwave interference a bit, shortwave sensitivity seemed good.</p><p>The whip antenna on the D-109 is 21 inches in length like its analog cousin, the D-219. <u><b>Warning, don't do this!</b></u> I removed the whip antenna by unscrewing the bottom mounting screw, and pulled the whip from the radio. Unfortunately XHData in their design wisdom have decided to solder a connecting wire directly to the bottom of this screw, and the wire broke off. There is no fixing this unless you pull the case apart, a nasty job on this radio, affirmed by Gary DeBock in his teardown of the D-109.</p><p>The radio works wonderfully on MW with an 18 inch tuned box loop. The sensitivity, already very good, is outstanding when coupled to the loop.</p><p>Bottom line so far: Great radio for mediumwave. I'm not an FM fan, so no FM testing was done. If you want something for shortwave, you had better be sure you live in a rural area away from high power AM stations. $30 seems a good price point for this radio. It's a keeper for me, and has become my morning driver radio.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhAM9iPUpzU0HlvaE4WV_Xs9RogbbtOUk33lviEpdQlNGAQO3hjBMnhXX8S4LQ9ihLesdnSzkLuoUtNh4tXzSt4qq7-31fu0RXwluXzjMQ0NKK3vQxjtJ-w2HNm1Gpdy_3CpNQkxqoa2VOh0fxp-Y1A6AxfZsvRt_N1GOWyuoTNVh9MkOP6-MxyDlTAQg/s1030/D-109-2.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1030" data-original-width="1024" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhAM9iPUpzU0HlvaE4WV_Xs9RogbbtOUk33lviEpdQlNGAQO3hjBMnhXX8S4LQ9ihLesdnSzkLuoUtNh4tXzSt4qq7-31fu0RXwluXzjMQ0NKK3vQxjtJ-w2HNm1Gpdy_3CpNQkxqoa2VOh0fxp-Y1A6AxfZsvRt_N1GOWyuoTNVh9MkOP6-MxyDlTAQg/w398-h400/D-109-2.jpg" width="398" /></a></div><br /><p><br /></p>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com1tag:blogger.com,1999:blog-4260200412608523752.post-59064661385201231432023-05-16T09:50:00.075-04:002023-05-16T12:14:32.840-04:00Notes On The XHData D-219 Analog DSP Radio<p>My D-219 came a couple of weeks ago and I've been checking it out. A fair amount of discussion has ensued about this radio, and I think feelings about it are generally positive. It is an analog DSP radio, using the Silicon labs Si4825 DSP chip. That to say, the tuning "mimics" the analog tuning of old school radios, but uses digital technology to do it. Amazon had it on sale for about $12, so I jumped at the chance to try it out.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhx0BOzTg9l3xtD3_GqOjnPF647-QVo3vontqBfDc1ciZEf_w-AK-WVfn3O8LzQNPLIXk_8_ueATQexRiXwwbxUjGydHVQUZNsgTWOXpIgpU_gb0Nt-nvBS79mOD80ThUrFC-nubY5Cxgw7c3MeoxZl-EbvjcserpDfrkvDbTdVSmKH4Ug4GZPvnNuI1Q/s1024/XHData-D-219.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="852" data-original-width="1024" height="333" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhx0BOzTg9l3xtD3_GqOjnPF647-QVo3vontqBfDc1ciZEf_w-AK-WVfn3O8LzQNPLIXk_8_ueATQexRiXwwbxUjGydHVQUZNsgTWOXpIgpU_gb0Nt-nvBS79mOD80ThUrFC-nubY5Cxgw7c3MeoxZl-EbvjcserpDfrkvDbTdVSmKH4Ug4GZPvnNuI1Q/w400-h333/XHData-D-219.jpg" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">The XHData D-219</td></tr></tbody></table><p>The fit and finish on this radio is very nice for a $12 radio. The tuning wheel tunes butter-smooth with no noticeable backlash, better by far than many. The radio measures 3 inches tall, 1-1/8 thick, and 5-3/16 inch wide, just about 1/2 inch wider than the RadiWow R-108. The whip antenna is 21 inches long as opposed to the 19 inch whip on the RadiWow R-108. The radio takes two AA cell batteries and they last admirably, even with the speaker engaged. It presumably will use rechargeables as well. A 5 volt adapter plug is at the top of the radio next to the headphone jack. A stereo headphone jack is also at the top (only mono delivered), right next to the radio's sliding ON-OFF switch. On the right side are the tuning wheel and volume control. A crisp, well marked dial scale faces frontward and beneath it is the sliding band switch, similar to those found on other inexpensive analog radios. The band switch looks and feels more robust than others I've owned. A nice hand strap also come with the unit. An English manual is provided, describing minimally how to use the radio.</p><p>The radio tunes mediumwave, shortwave, and the FM band. Note that this radio is made predominintly for the Asian markets. It only tunes mediumwave from 522 to 1620 kHz, and that at only 9 kHz channel steps, used outside of the western hemisphere. Two FM ranges are present - 64 to 87 mHz, and 87 to 108 mHz. There are nine shortwave bands, covering broadcast segments from 4.75 mHz to 22.0 mHz.</p><p>The following comments refer to the mediumwave band. In particular, I'll discuss the tuning quirks of this radio. I have other analog DSP portables which tune similarly.</p><p>I'm impressed by the mediumwave sensitivity, it's very good. Examples: On weak daytime signals, it was better than my other DSP analogs, the Sangean SR-35 and the inexpensive ($13) Dreamsky pocket portable. It was better than old school analog Sony ICF-S10MKII. Against the old school Tecsun R-9700DX, a much larger radio with longer loopstick, it was no match of course. It wasn't quite up to par in sensitivity with the DSP all digital RadiWow R-108, but close.</p><p>Tuning is interesting to say the least, pitting a 9 kHz channel step against a 10 kHz band, and the already existing tuning wonkiness of these analog DSP chips. Daytime tuning may seem pretty normal. Nighttime is a different story. On moderate to strong stations, there may be three, five and sometimes even seven tuning peaks as you tune through a signal. This to me suggests a wide AFC (automatic frequency control) bandwidth in signal selection, possibly up to 27 kHz (3 channel steps) either side of the actual tuned center.</p><p>Note that these analog DSP radios don't use a traditional stepped tuning encoder. They are tuned with a simple 100K ohm (the SiLabs versions) or 10K ohm (most Chinese chip versions) potentiometer. The chip reads a voltage across the potentiometer and determines the tuned frequency from that. Software then decides what to do thereafter.</p><p>Checking the software manual for the Si4825 chip, one encounters the UNI-AM software switch on the DSP chip, named for "Universal AM". This is likely what is used to defeat the normal default AFC range of 1.1 kHz. I don't see the extreme 3/5/7 peak characteristic in the Sangean SR-35 or the Dreamsky. Each peak as you tune off signal center is reduced in audio by a couple of dB, mimicking the analog tuning of old. It is apparent that a signal's strength needs to be above a certain threshold to engage this multi-step tuning curve. Weak signals won't engage it. To-wit, a signal above this threshold is essentially "captured", forcing the tuning to its channel. This presents a problem in trying for weak stations between stronger channels.</p><p>See the example chart just below. I'll describe a typical experience in tuning this radio at night where many signals at varied strengths are present.</p><p><span style="font-family: courier;">9kHz Offset Station we are trying for</span><br /><span style="font-family: courier;">---- ------ -----------------------------------------</span><br /><span style="font-family: courier;">612 2 kHz 610 WTEL Philadelphia, PA (medium strong)</span><br /><span style="font-family: courier;">621 1 kHz 620 WSYR Syracuse, NY (very weak)</span><br /><span style="font-family: courier;">630 0 kHz 630 CFCO Chatham, Ontario (medium strong)</span><br /><span style="font-family: courier;">639 1 kHz 640 WNNZ Westfield, MA (weak)</span><br /><span style="font-family: courier;">648 2 kHz 650 WSM Nashville, TN (very strong)</span></p><p>My listening post is in western NY near Rochester, about 75 airline miles west of Syracuse. With the D-219, catching WSYR-620 or WNNZ-640 in Massachusetts is hit and miss. This is because they are sandwiched on either side and between two much stronger signals. The stronger signals engage the 3/5/7 step tuning algorithm.</p><p>Example: In this 610-650 kHz range, WSM-650 was the strongest of all during this test. I centered WSM-650 for strongest audio, approaching from a higher frequency. This will occur at 648 kHz on this radio. Tune left one peak, and WSM's audio reduces by a couple of dB. Tune left again and WSM's audio reduces again a couple of dB. After two tuning steps, we should be tuned to 630 kHz, but the radio is still tuned to 650 kHz due to the AFC capture effect. Tune one more step to the left (621 kHz actual), and suddenly the radio tunes to CFCO-630. Why? AFC capture effect again. We have skipped over WNNZ-640 because it is extremely weak and below the capture threshold. The same for 620 WSYR, the station we should be tuned to - too weak. And since WSM at 650 kHz was the strongest signal, stronger than CFCO, when we were actually tuned to 630 kHz, the radio remained on WSM (648 kHz actual, with audio reduced). Important!!! - the tuning direction is important here - we are tuning downward and off the strongest signal, we are not approaching the strongest signal. More about this phenomonym explained below.</p><p>Turning the radio off, then on, sometimes has an interesting effect. In the above situation where we landed on CFCO-630 coming from 650 WSM, turning the radio off then back on may indeed land you on 620 kHz!!</p><p>In another case of downward tuning, where CFCO at 630 kHz was in a deep fade and virtually non-existent signals at 620 and 640 kHz, tuning progressed from WSM-650 directly to WTEL-610, bypassing 630 CFCO. Nothing was heard in between. It was the capture effect at work again.</p><p>Notice for the above scenarios we are tuning downward in frequency. Tuning upwards from 612 kHz will have a different result because we are approaching adjacent channels from a different direction and adjacent channel signal pair strengths will differ, with the strong signals capturing first if above the software-set threshold.</p><p>On old school, traditional analog radios it was fairly easy to figure out what frequency you are tuned to. We'd go to a known channel and count the channel "bumps" as you tuned up or down. It's not totally possible with the DSP analogs, at least the D-219. AFC capture may force-tune to a stronger channel one, two, or three steps away.</p><p>This is where a passive loop or helper antenna might benefit this radio, by increasing signal strengths of weaker channels so they trigger the AFC to capture. Care should be taken not to overload the radio with too much signal. My 18 inch passive, tuned loop is too much for this radio. Possibly a 12 inch passive loop might not overload. My testing a few years ago showed that a 12 inch loop was roughly equivalent to an 8 inch ferrite coil. It will provide plenty of signal.</p><p>Shortwave is a problem with this radio if you are in a high signal area near one or more mediumwave transmitters. Intermod and overload bleed through is severe throughout the shortwave spectrum. I am unable to test this radio on shortwave anywhere near the city of Rochester because of it. My next trip to the country I'll do that. I'm not an FM fan, so no FM testing was done.</p><p>All-in-all, I like this radio quite a bit. It has a great amount of what I like to call "fun factor". Mediumwave sensitivity is good and better than most. If XHData decides to make a 10 kHz step version for the North American market, I'd go for it. It's perhaps the best but least expensive radio I've bought.</p><p><b>EXTRA - MORE DISCUSSION ABOUT ANALOG DSP TUNING AND THE XHDATA D-219</b></p><p>I've studied the software manuals in pretty good detail for these analog chips and also the digital ones. Here's what I have gleaned from them.</p><p>Document AN610.pdf covers the American SiLabs 48xx analog chips. Asian clones of the DSP chip are slightly different in their operation. I hesitate to use the word "clones", as the Asian chips have a few more bells and whistles than the SiLabs ones. To our advantage, I might add.</p><p><u>AMERICAN SILABS CHIPS:</u></p><p>Channel step size (9 or 10 kHz) is set by software at power on time.</p><p>AN610.pdf:</p><p><i>"3. The channel spacing is configurable for the AM band mode only. System controller can select between 9 (9 kHz) and 10 (10 kHz) channel space. Note: SW is set to 5 (5 kHz) by default, FM to 100 kHz."</i></p><p>The document does not indicate that any other value can be set, other than 9 or 10 if in AM band mode.</p><p>The analog tuned DSP chips don't have a traditional stepped tuning encoder. They tune using a 100 K ohm linear potentiometer. A voltage is impressed across the pot and when you rotate the pot knob the DSP chip reads the voltage, and from the voltage, the controller software calculates a frequency to tune to.</p><p>If we are set to a 9 kHz step, tuning proceeds to the closest 9 kHz boundary. If we are set to a 10 kHz step, tuning proceeds to the closest 10 kHz boundary.</p><p>Note: The analog CCrane Radio EP Pro has a switch on the back to select 9 or 10 kHz step. It must force the radio to go through a power up sequence to accomplish this.</p><p>Filter bandwidth for AM looks to be fixed, i.e. not able to be set at power on, probably at about 6 kHz. Remember, we are talking about the analog DSP chip here, not the 473x digital version.</p><p>The digital series chips (the 473x models like the PL-380, etc.) are tuned totally differently. Tuning (internally at the software level) is in finer graduations and by default is to 1 kHz. The user usually has control of the step size in the AM band - 1, 9, or 10 kHz. They use a regular mechanical encoder, not a potentiometer.</p><p><u>ASIAN ANALOG CHIPS, commonly the KT0932m, KT0936m, KT0913:</u></p><p>Again, step size is set by software at power on time.</p><p>The document I have on these indicates the step size can be set at not only 9 kHz or 10 kHz, but also the 1 kHz step size. The tuning mechanism is a 10 K ohm potentiometer here. The KT0913 supports up and down channel buttons, the other two do not.</p><p>Notable in the Asian documentation is the raw sensitivity of these chips is claimed to be a bit better than the SiLabs chips, by about 6 dB. 16 µV @ 26 dB signal-to-noise ratio.</p><p>Filter bandwidth for AM has some flexibility. It can be set between 1 and 5 kHz at power up. I don't see a 6 kHz filter anywhere.</p><p>The Asian equivalent to the SiLabs Si473x series is the KT0935r.</p><p><u>Bottom line-</u></p><p>If a radio uses the Asian analog DSP chip, 1 kHz step size on AM is possible if the designer sets it at power up time. American SiLabs chips can only step at 9 or 10 kHz.</p><p>An interesting YouTube video on the XHData D-219 by Todderbert can be seen here:</p><p><a href="https://www.youtube.com/watch?v=lrGS6DAZHsg">Todderbert D-219 Review</a><br /></p><p>There is a comment by a Anna P in this video link that explains that these chips have a wide AFC and can retune the frequency when the signal was not at the center by itself. I'll paste her full explanation here, as it's an interesting read. I'm not sure I'm in total 100% agreement, but there is merit to much of what is stated. Thanks to Jay Allen for the tip on this comment.</p><p><i>"Anna Plojharová - I don't think you need a dedicated "10kHz" version. These analog tuned DSPs use rather wide AFC function which retunes the radio to the exact signal it sees. It first tunes to the exact frequency corresponding to the knob position and looks for carrier there. If not found, it gradually widens the frequency range till it finds one and then retunes properly on it (tunes the antenna). If this carrier is more than half of the tunning control step away (so there is other position of the dial), it artificially reduces the volume in order to get the "correct tuning" feeling, but that is 100% artificial behavior, the real reception is tuned exactly onto that carrier found. Usually the total search range for the given dial position is way wider than channel spacing, often 30..50kHz (so +/-3..5 channels). And the artificial "detune volume reduction" is often temporary - if there is really just that single carrier, after few seconds many chips just take that as "the desired station" and bring the volume back up."</i></p><p>The only issue could be, if two stations are the same frequency difference from the dial position, then it becomes tricky to convince the radio to select the weaker one, there the correct tuning step does help.</p><p>Todderbert's AM bandscan shows that the radio's tuning does not automatically retune to center peak of 10 kHz station boundaries. That implies to me that a 10 kHz spacing model would be preferable and work better here in the western hemisphere.</p><p>AFC width is selectable in software (the so called "UNI-AM" parameter), but only two choices - a default value of 1.1 kHz and what they call "Universal AM Band", which is an unspecified but wider AFC width. My suspicion is if "UNI_AM" is chosen, the radio may respond well to either 9 or 10 kHz spacing. HOWEVER, important to note here, the AN-610 software document says this is only available in the Si4827 chip models. The D-219 has the 4825A, per Kelly (thanks for checking Kelly).</p><p>On my CCrane Radio EP Pro, the one with the 9-10 kHz spacing switch, if I set to 10 kHz and tune to a station, then switch the slider over to 9 kHz, the tuning is off and does not recenter. This is dramatically shown on WYSL-1040 here, a very strong station. Tuned perfectly to 1040 kHz in 10 kHz spacing mode, then switching to 9 kHz where the new closest channel would be 1044 kHz, WYSL virtually disappears as the radio is now tuned 4 kHz away from 1040 kHz. Clearly, 9 kHz spacing does not recenter to a 10 kHz boundary. The wide AFC statement clearly does not apply to all analog DSP radios.</p><p><br /></p><p></p>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com0tag:blogger.com,1999:blog-4260200412608523752.post-21296615133037834232022-10-06T15:09:00.065-04:002022-10-06T16:03:07.219-04:00The Portable Greyline Map<p>Knowing where there is daylight and darkness over the earth at any given time is somewhat of a necessity when DXing shortwave or mediumwave. There are online maps, sure. But what if you had your own personal daylight/darkness map you could save to your computer and click on any time you wish?</p><p>Look for the download at the upper right of this page.</p>
<p>The Daylight/Darkness Greyline Reference Map is produced by my Radio Data MW program.</p><p>Included is a GoogleMap-based, HTML-driven map which shows the current daylight/darkness state over the earth. Being a Google-based map, it is zoomable and scrollable. You may choose map view or satellite view. If desired, a home location may set by scrolling the map and clicking "<<Set Home". This will allow you to return to the same reference point as long as the current map page remains open. Depending on your brower, latitude and longitude may be saved across map restarts.</p><p>Draw tracks, check distances and bearings to points, all displayed in the marker tooltip</p>
<p>You must have an internet connection to view the map.</p><p>The file download is at the upper right of this page. It's a small 19 KB. For more details on usage, be sure to read the readme.txt file contained in the download.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgO0DQttxhcAATBMIyOjQXD1vgagZlwJhSnuf9whWACgvl3MbY7M1OQ9_rVjB5XXMgZQThqg-eJBya6Txqcr3TTUWe0jvO4dfhdcTAz93y8vFGwEwbofF_6cuyrP9Os1sjgBFiZiKWJ4x4zxrHNV--s3iR_fnpp4P31VgtqZYt4BFsnVM_83le_BRkuCA/s1214/greyline_map.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="866" data-original-width="1214" height="456" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgO0DQttxhcAATBMIyOjQXD1vgagZlwJhSnuf9whWACgvl3MbY7M1OQ9_rVjB5XXMgZQThqg-eJBya6Txqcr3TTUWe0jvO4dfhdcTAz93y8vFGwEwbofF_6cuyrP9Os1sjgBFiZiKWJ4x4zxrHNV--s3iR_fnpp4P31VgtqZYt4BFsnVM_83le_BRkuCA/w640-h456/greyline_map.jpg" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">The Portable Greyline Map</td></tr></tbody></table><div class="separator" style="clear: both; text-align: center;"><br /></div>
<p><b>INSTALLING</b></p>
<p>No install necessary! The map is HTML-based, so no regular install is necessary. Simply unzip the downloaded file and click on the map file to run. The map will open up in your web browser. The map is self-contained. Again, you must have an internet connection to view the maps.</p>
<p><b>THE NIGHT/DAY OVERLAY OR GREYLINE</b></p>
<p>Greyline propagation, or propagation along the earth's sunrise/sunset terminator, is very noticeable on the 160, 80, and 40 meter ham bands and lower shortwave bands. Medium wave signals can and do travel that path as well. </p><p>A night/day overlay can be drawn or removed by toggling the Greyline button at the top of the map. The overlay will show the areas of the earth in darkness, including the earth's terminator - the band of twilight surrounding the earth.</p><p>The night/day overlay shows the width of the earth's terminator and its transition from total darkness to the sunrise and sunset edge. The actual sunrise or sunset point is the edge where the overlay disappears. The lightest band of the overlay is civil twilight, where the sun is just below the horizon to a point 6 degrees below the horizon. The next darkest band is nautical twilight, where the sun is between 6 degrees and 12 degrees below the horizon. The next darkest band is astronomical twilight, where the sun is between 12 degrees and 18 degrees below the horizon. The darkest area is where total darkness exists, where the sun's position is greater than 18 degrees below the horizon. Medium wave and other signals, as described above, can propagate along the terminator at greatly reduced signal attenuation - and are often received at astonishing distances.</p><p>The night/day overlay gets UTC from a software call to Javascript. Javascript calculates UTC from your computer clock, as it knows the time difference in local hours to UTC. So you must have your computer clock set correctly and with the proper time zone. Long story short, the night/day overlay is always synced to UTC (at map page load time). The overlay is static until you refresh the page or press the "Update" button, where it will move to its new position.</p><p>For mediumwave enthusiasts: Some US stations transmit at reduced power during a period called "CRITICAL HOURS". The FCC defines Critical Hours as the first two hours of daylight after sunrise and the last two hours of daylight before sunset.</p><p><br /></p>
RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com0tag:blogger.com,1999:blog-4260200412608523752.post-87849315847264038692022-09-06T04:19:00.003-04:002022-09-06T04:23:16.785-04:00shango066's Station Tour Of KYET-1170<div>YouTube contributor shango066 has produced one of the most fascinating station tour videos I've ever seen. It is of AM Stereo C-QUAM station KYET-1170 in Golden Valley, Arizona. KYET broadcasts daytime 6,000 watts to a 190 ft. monopole tower, omni-directionally, and 1 watt at night.</div><div><br /></div><div>See AM broadcast radio at its grittiest in the desert of western Arizona!</div>
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<br>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com0tag:blogger.com,1999:blog-4260200412608523752.post-2372797774083601262022-05-04T07:45:00.013-04:002022-05-27T17:32:25.393-04:00The Loop-on-Ground Antenna For The Noise Challenged<p>In this article, we'll discuss the Loop-on-Ground antenna and how I've used it to advantage for mediumwave and shortwave DXing in an extremely RFI-ridden environment. We'll also discuss sources of RFI and how they might be minimized.</p><p>Those of us who have been in this hobby of DXing for many years are lucky to remember the days of no problematic electrical interference. My DXing days go back to about 1959 or 1960. It was about then that the modern-day light dimmer was conceived, using newly-developed thyristors and triacs to vary the "duty cycle" (on/off time) of the full AC voltage. It was the birth of the RFI avalanche.</p><p>Electronic hash proceeded quickly. Radio frequency interference (RFI) - the crescendo of noise on the bands - is becoming virtually impossible to identify and corral. Back in the 1980s when it started getting worse, it was still possible to identify sources and eliminate them using time-worn line-choke-suppression methods. Now, not so much. The genie is out of the bottle and it ain't going back in.</p><p>One of the best tools I have found to identify RFI is a spectrum analyzer. No, a $2000 unit isn't necessary. You already have one if you own an SDR receiver. I have an SDRPlay RSP1a, purchased at $119 U.S. and it's quite easy to take a look at any frequency from 10 KHz on up to see where the problem areas are. Spread a short wire across the floor in the house, connect it up, and you will see all kinds of mysterious RF. A pocket or portable sniffer receiver can work for this too but it's much easier to see the RFI's extent on an SDR receiver's spectrum display. The sniffer receiver is better used to locate the RFI.</p><p>I currently use my RadiWow R-108 as a sniffer receiver when walking around the house or property. This is used once the RFI "problem" frequencies are identified on the analyzer. Your Tecsun PL-380, PL-310, or other portable receiver can do the same.</p><p>The next two sections of this article, <u>BIG OFFENDERS</u> and <u>ANTENNA SOLUTIONS FOR NOISY ENVIRONMENTS</u>, are reproduced here for clarity, and as a re-introduction to low noise antennas. They originally appeared in my article <a href="http://radio-timetraveller.blogspot.com/2020/12/the-rfi-menace-and-reduced-noise.html">The RFI Menace And Reduced Noise Antennas</a>.</p><p><b>THE BIG OFFENDERS</b></p><p>Let's go over the big RFI offenders to our DXing. The big offenders at my DXing home are:</p><p>My Hewlett-Packard 24 inch computer monitor. Huge, wideband, low frequency buzzing in a range across the VLF, longwave and lower mediumwave bands, particularly in the 300-900 KHz segment. The switching power supply creates some of this but the majority comes right off the screen's surface when the display is lit. Efforts to reduce this RFI have only been mildly successful, but luckily its range is only about 15 feet. The downside is the radios need to be within 15 feet of the monitor, particularly the SDR.</p><p>My laptop's switching power supply. I have a recent (2020) Acer Nitro 5, 15.6 inch, with AMD Ryzen 5 4600H mobile CPU. Huge, wideband, low frequency hash between 0 and 600 KHz. Virtually all of this disappears when running on battery only. You can't run on battery forever, however.</p><p>Old style fluorescent lighting, particularly the old 4 ft. shop lights. Best is to just keep them turned off.</p><p>Light dimmers. Don't use them. Keep them off or remove them.</p><p>LED light bulbs for house lighting. The bad ones create a high frequency hiss. Luckily the range is only a few feet, but the house is full of them now due to power saving measures. Use good quality LED bulbs. Philips has been highly recommended.</p><p>Low voltage lighting used in the kitchen. Lots of wiring through the walls go to a transformer box in the cellar. When the lights are on they inject an additional huge buzz at the lower end of the mediumwave band, peaking at about 550 KHz. The emissions from these range throughout the house. The condition is virtually eliminated by keeping the lights off.</p><p>A myriad of switching "chopper" style wall transformers. Some are much worse than others. Try to identify the worst offenders. I try to put all of these on power strips so I can switch them off when not in use.</p><p>Unknown sources of frequency spikes. Strong 10 KHz spaced spikes from 9 MHz to 16 MHz, peaking in the 9.5-9.9 MHz and 10.7-12.5 MHz area. This one is intermittent. It can last ten minutes or an hour or more, then disappears. <strike>I have not ruled out that this signal may be coming from the mains feed to the house.</strike></p><p>**Note: this RFI source just above has been identified. It comes from a $2000 Fisher & Paykel kitchen refrigerator. Fisher & Paykel is a major appliance manufacturer which is a subsidiary of Chinese home appliance manufacturer Haier. It is a multinational corporation based in East Tamaki, New Zealand. In 2012, Haier, a major Chinese appliance manufacturer, purchased over 90% of Fisher & Paykel Appliance shares. Partial solution: wrapping the power line cord through two Workman RFC-1 snap ferrite cores has reduced the problem 50%. More cores have been ordered.</p><p>A new 43 inch Toshiba smart TV and DISH satellite box combo. Tremendously strong RFI, a high-pitched squeal in the LW and MW bands coming out of these boxes out to a 6-8 ft. radius, which then couples to lines. It might be possible to put these on a switchable power strip, but then you have the device reboot problem every time you want to use them. Satellite box boot time is often 5 minutes. That's a no-go.</p><p>Those are just the biggest offenders. Not mentioned is the RFI coming off the computerized de-humidifier in the cellar, the computerized water conditioning system, and the two computerized heat pumps hanging off the back of the garage.</p><p>So you can see the frustration. It's not practical to try to eliminate all of this RFI unless you'd like a lifetime career in RFI removal. I suspect this is the case almost everywhere.</p><p><b>ANTENNA SOLUTIONS FOR NOISY ENVIRONMENTS</b></p><p>Being a ham as well, I've experimented with just about every wire antenna you can imagine over the last 60 years. My days of winding power line chokes are over. Common-mode chokes, current isolators, et al, are the rage these days - these to reduce RF pickup on the feedline and to lessen the possibility of the feedline from becoming part of the antenna system. They can help, but they are a Band-Aid to the real problem. Why not lessen the noise in a different way? My solution is to build inherently quiet antennas which are resistant to noise, <i>and feed them correctly</i>. </p><p>Three things are important.</p><p>1. Get the antenna well away and out of your house.</p><p>An end-fed longwire attached to your shack window fed with 15 ft. of coax across the floor isn't going to do it. If possible, on your lot, put the feed point as far away as you can. This, for starters, is one of the most important things you can do. Don't worry about cable feed length. Coax feed at mediumwave or even shortwave frequencies has minimal loss. 100 feet of the old 50 ohm RG-58 on mediumwave presents only about 0.37 dB signal loss, virtually unnoticeable. RG-6A TV coax, 75 ohm, is even less at about 0.28 dB per 100 ft. I use RG-6A here almost exclusively, as it is cheap and readily available through many suppliers.</p><p>So, get that feed point as far away from your house as possible.</p><p>2. If you can, choose an antenna that is basically a short circuit. <i>What did you just say?</i></p><p>Loop antennas are essentially short circuits to high frequency impulse noise. Long wires, verticals, and dipoles are not. They are RFI magnets, and particularly so if they are not balanced antennas (the dipole is at least balanced). Much of the high frequency noise component of RFI is short circuited in the loop. Small loops are even better for noise suppression, but their drawback is they often need active amplification due to lower signal delivery. Loops work well when placed close to the ground and you don't need high supports for wires.</p><p>They can also be laid flat on the ground itself which reduces RFI even more. This is where our Loop-on-Ground antenna will come in.</p><p>3. Use an isolating transformer <i>at the antenna feedpoint</i>. Very important. Feed any antenna with a transformer-balun isolating device, even if it is naturally a 1:1 match. There must be no common ground connection between the coax feedline and the antenna, i.e., between the primary and secondary of the transformer-balun. The antenna should remain floating and the coax remain floating. This isolating-matching device does three things which help abate noise:</p><p> 1) Matching the antenna greatly increases received signal strength. Increasing signal strength often will raise the signal above the noise floor. Remember when receivers had preselectors to peak the antenna, which made the difference of hearing a signal or not? This is what a broadband matching transformer is actually doing - matching the antenna to the receiver across a wide range of frequencies.</p><p> 2) The transformer, at least the one we will use, totally isolates the antenna from the receiver, eliminating the direct wire connection and lessening RFI <i>picked up by the antenna</i> from transferring to the coax. Much of the RFI will be consumed in what I call the secondary, or load side (antenna side) of the balun, as it appears as a direct short to the high frequency component of noise.</p><p> 3) The transformer/balun reduces antenna loading because it presents a proper load impedance to the antenna. Loading down the antenna destroys bandwidth and lowers signal strength. Take a longwire for example. A longwire antenna has an inherently high feed impedance, generally 450 ohms, nothing near the usual 50 ohms of a receiver. With no matching device, the input signal delivered to the receiver is a simple resistance ratio. The signal is delivered through a 450 + 50 ohm series divider. The receiver gets 50/500ths of the available signal without the proper transformation. That's 1/10 of the signal being picked up by the antenna! No wonder my receiver can't hear!</p><p><b>THE LOOP-ON-GROUND ANTENNA, or LoG</b></p><p>Now we get to the Loop-on-Ground antenna, or LoG. The LoG antenna is another variation of the close-circuited loop, only it lays flat on the ground. It is also best fed with a balun. KK5JY has the preeminent article on the Loop On Ground antenna, with illustrations. Be sure to check it out. It is the inspiration for my Loop-on-Ground which I use for mediumwave and shortwave.</p><p><a href="http://kk5jy.net/LoG/">http://kk5jy.net/LoG/</a></p><p>KK5JY's LoG antenna performs best from about 2-8 MHz, at about 60 ft. total wire length. Wanting to try a LoG for mediumwave, I decided to buy a 100 ft. spool of insulated, 18 gauge wire. These are readily available from Amazon for about $9. I ordered one and experimented.</p><p>KK5JY, being a ham, based his design on covering the 160, 80, and 40 meter ham bands. We will increase the loop size to cover the mediumwave band. It will be effective all the way up to the 31 meter band and beyond.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjE7SL-oeYbYascdKh3xu4zWxIAiEj3ypJg8qPYzRo1iYsfhTWt4VmypLM3n4wJwjtii1lqM0tpFouHH5BideVG-mJ_uIsbKJXXG9YS_g1SsWEplJj1NqqlY8L7w9Z-83ii8kk7kFswqPZGs3euzDfv34439YIxWyw-YDt8KRuh7r6idd7gmsYBcLB7cA/s1024/outside-balun_1024x726.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="726" data-original-width="1024" height="454" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjE7SL-oeYbYascdKh3xu4zWxIAiEj3ypJg8qPYzRo1iYsfhTWt4VmypLM3n4wJwjtii1lqM0tpFouHH5BideVG-mJ_uIsbKJXXG9YS_g1SsWEplJj1NqqlY8L7w9Z-83ii8kk7kFswqPZGs3euzDfv34439YIxWyw-YDt8KRuh7r6idd7gmsYBcLB7cA/w640-h454/outside-balun_1024x726.jpg" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">The Nooelec 9:1 balun connection</td></tr></tbody></table><br /><div><div>The LoG is generally arranged in a square and fed at one corner. It is somewhat directional, having an extremely flattened hourglass pattern, with slight nulls at the feed corner and the corner opposite the feed. In practice I have found its directionality hardly noticable. Both high and low angle reception are good, within its range, with high angle being predominant. Studies have shown that the pattern is similar to a big ball set on the ground.</div><div><br /></div><div>Don't have concerns about low angle reception. As I write, I am tuned to 530 KHz at 3 AM in the morning here on the east coast of the U.S. On the channel fighting it out are CHLO-530, Brampton, Ontario (193 km @ 250 watts), and 530-Radio Encyclopaedia in Cuba (2300 km).</div><div><br /></div><div>Best results are when the overall loop length is about 15% of a full wave for the frequency of interest. As stated, a 60 ft. total length works well for the 2-8 MHz range. It is usable to about 15 MHz, though sensitivity drops off above the 25 meter band (11.500 - 12.200 MHz).</div><div><br /></div><div>Initial testing for KK5JY's 60 feet of wire on the ground were not encouraging in the mediumwave band. Signal strengths were down except at the very high end. 100 feet total wire length works out to an optimal 1480 KHz, and greatly increases the signal strengths throughout mediumwave. 120-140 feet should be even better. Ballpark ranges are thus: 530 KHz - 278 ft., 1700 KHz - 86 ft.</div><div><br /></div><div>Lay your 100 ft. of wire out in a square, 25 ft. to each side, and feed it at a corner. Exact square shape is not paramount, but try to keep it as close to square as possible. Remember, loop area is important - we want as large an open area as possible. The loop can be layed right on the surface of the ground or pinned down with U-nails. Some have even dug it in an inch or two. This winter, mine has even been buried under 12 inches of snow for the last month, and the LoG has still performed admirably.</div><div><br /></div><div>The loop must be fed with a balun and remain ungrounded. KK5JY's 2-8 MHz loop exhibited a feed impedance orbiting the 400 ohm range. That's about 8:1 for a 50 ohm coax feedline. I'm using a commercial Nooelec 9:1 receiver balun, available from Amazon for under $20. It has proven to be close enough, though I'm planning on experimenting with different homebrew toroid cores and turns ratios. My loop is fed with 100 ft. of RG-6A coax (75 ohm), though I've experimented out to 175 ft. I've found the 100 ft. minimum distance from the house to be adequate in relieving 95% of the noise problem. It is important not to ground any leg of this antenna as that will upset its balance. Also do not earth-ground the coax shield. Early models of the Nooelec 9:1 balun (v1) joined the primary and secondary windings electrically through a center-tapped secondary. Be sure to get the new version of the Nooelec balun. They have eliminated this connection.</div></div><div><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgnFthpLuCvT7Sw34x_kli1BvNNoIZ7z62sutVBo6injxT43FHGPlMzXVqnamvkwGkrUM_hh6ccjGgEBbKRXOpSoAHcb7lIrvNHF36hUYtkjlDBkhh8nxq9pShErRbu8TE-fIucs7hQKHxk1sPIGsGaVupOHBUM5vY1u8Zf9BVPx5W68zuDDu3TGaiVJw/s420/balun-one-nine.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="281" data-original-width="420" height="214" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgnFthpLuCvT7Sw34x_kli1BvNNoIZ7z62sutVBo6injxT43FHGPlMzXVqnamvkwGkrUM_hh6ccjGgEBbKRXOpSoAHcb7lIrvNHF36hUYtkjlDBkhh8nxq9pShErRbu8TE-fIucs7hQKHxk1sPIGsGaVupOHBUM5vY1u8Zf9BVPx5W68zuDDu3TGaiVJw/w320-h214/balun-one-nine.jpg" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">The Nooelec Balun One Nine (v2)</td></tr></tbody></table><br /><div><div>The LoG is an excellent low noise performer. My 100 ft. length lying on the ground shows close to 15 db less noise than a 6x12 ft. flag antenna, with about equal signal strengths. Similar results were found with tests in the tropical band (60 meters). The difference gained is in the substantially better signal-to-noise (SNR) ratio. A 15 dB reduction in noise while holding the same signal strength as the small flag antenna is a 15 dB SNR improvement!</div><div><br /></div><div>The antenna is fairly non-directional, so no competition is claimed with the directional beverage-on-ground (BoG) or traditional above ground beverages. Internet reports have made the claim it works well in some localities but maybe not so well in others. Discussion of ground conductivity under the LoG then ensued, with pros and cons. I suspect many dismiss it outright without really doing a little deeper experimentation. Initial reaction is always "how can this work if it is lying on the ground?"</div><div><br /></div><div>Signals need only to break the atmospheric noise level by a few dB to be received. But first you must lessen the electrical hash so it is below that level. With the LoG, general atmospheric noise levels here are well under a microvolt from MW through 30 MHz, somewhere in the -110 to -120 dBm area, depending on the band. Remember, -107 dBm is one microvolt signal level, a very small signal. Check out KK5JY's page where he has produced some signal graphs.</div><div><br /></div><div><b>LET'S SEE SOME RESULTS</b></div><div><br /></div><div>The best way to show off the LoG antenna is to show its reception advantages on an SDR's spectrum and waterfall displays. Using an SDRPlay RSP1a and SDR-Console gives a dramatic result.</div><div><br /></div><div><u>BEFORE</u> - SDR using a 100 ft. longwire, run from shack window out to a tree. Longwire fed at the window through an RF Systems Magnetic Longwire Balun to a short length of coax to the receiver. The electrical hash is deafening, as seen in the waterfall.</div></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhgCac0mKcWFav6AwQ7x2dyJ7Hp6YFAstEhu8VUeQNKr3Ibo7n_20fQO7fxitnEq_-28vPG79OL6SSdKnU3zcsqn7fWTWrMBPSLXpjYaQsjY7-AjcRG86-B-YOCgBWAFYCpttk-ArnWxQos-xGlHBva94svMrmQfjhBf4Am6RHTPsjKCmVFu1x80UEckQ/s1548/sdr-console-before-530.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="955" data-original-width="1548" height="394" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhgCac0mKcWFav6AwQ7x2dyJ7Hp6YFAstEhu8VUeQNKr3Ibo7n_20fQO7fxitnEq_-28vPG79OL6SSdKnU3zcsqn7fWTWrMBPSLXpjYaQsjY7-AjcRG86-B-YOCgBWAFYCpttk-ArnWxQos-xGlHBva94svMrmQfjhBf4Am6RHTPsjKCmVFu1x80UEckQ/w640-h394/sdr-console-before-530.jpg" width="640" /></a></div><br /><div style="text-align: center;">----------</div><div style="text-align: center;"><br /></div><div style="text-align: left;"><u>AFTER</u> - SDR using the Loop-on-Ground antenna and fed with 100 ft. of coax. No hash.</div><div style="text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgS0jw0TY5EoKrFXBrI_AwGwWzjfMnYuu9H4_A_N6aG0dzJHgUCPYgXDURWGeMbXMn4Ta2Zy9VM7v7z1LLcpT4KJIolUdwCWL4SPKP4kaEeKT1rNSJsb9aQv1ldoD4-06mW2zpNgROssv3oGAPq7H4SanNctcg_IFYXT4sYrUTL0M3EzGfVf4AwlAuixw/s1548/sdr-console-after-530.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="955" data-original-width="1548" height="394" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgS0jw0TY5EoKrFXBrI_AwGwWzjfMnYuu9H4_A_N6aG0dzJHgUCPYgXDURWGeMbXMn4Ta2Zy9VM7v7z1LLcpT4KJIolUdwCWL4SPKP4kaEeKT1rNSJsb9aQv1ldoD4-06mW2zpNgROssv3oGAPq7H4SanNctcg_IFYXT4sYrUTL0M3EzGfVf4AwlAuixw/w640-h394/sdr-console-after-530.jpg" width="640" /></a></div><br /><div style="text-align: left;"><div>We are tuned to 530 KHz in both examples. It's 3:14 AM in the morning in western New York (display time is in UTC, 08:14). </div><div><br /></div><div>In the first example, on the 100 ft. longwire, look at the broadband electrical hash saturating the band. It is running S5 on the scale at left. There are signals there at the S8 level, but they are not intelligible due to poor signal-to-noise ratio.</div><div><br /></div><div>Now, look at the second example, using the LoG antenna. No electrical hash. What you see on the spectrum display is the atmospheric noise level, just above S1, about 0.3 microvolts. The signals at 530 KHz are at S8, and we have multiple signals. In the headphones are two stations: On the channel fighting it out are CHLO-530, Brampton, Ontario (193 km @ 250 watts), and 530-Radio Encyclopaedia in Cuba (2300 km).</div><div><br /></div><div>The difference is in bettering the signal-to-noise ratio. In the LoG example, signals are a full seven S-units out of the noise, proof-positive that an antenna lying on the ground can work. Again, don't worry about low angle reception problems. 530-Radio Encyclopaedia in Cuba at 2300 km has a calculated arrival angle of about 7 degrees.</div><div><br /></div><div>I also enjoy SWLing. My 100 ft. LoG is effective to the 31 meter shortwave band and beyond to 25 meters. Better results for higher frequencies can be had by shortening the wire length some. One of my favorite things to DX is Asia as the sun sets there. If conditions are good, signals just pop on the 31, 41, and 60 meter bands with the 100 ft. LoG. Right now I am tuned to the BBC/English service at Kranji, Singapore on 9580 KHz (125 KW) as I write at 1115 UTC (15,100 km distant). They are arm-chair copy.</div><div><br /></div><div>An excellent 16 page thread discussing the LoG antenna and matching techniques can be found on the QRZ forums. It is well worth a read.</div><div><br /></div><div><a href="https://forums.qrz.com/index.php?threads/loop-on-ground-antenna.622669/">https://forums.qrz.com/index.php?threads/loop-on-ground-antenna.622669/</a></div><div><br /></div><div>Testimonial from that thread:</div><div><br /></div><div><i>"Give it a try and post back here with results. I would like to hear how it works out for you. Just do not panic when you first hook up the antenna. Initially it will look like a Dumb (Dummy) Load because there is no noise, and signal levels will be down. But SNR (signal-to-noise ratio) levels will more than make up for signal loss. A signal level of -100 dBm is a HOT signal when the noise level is down at -140 dBm, that leaves you 40 dB SNR, a crystal clear signal."</i></div><div><br /></div><div><b>FEEDING A POCKET OR PORTABLE RADIO HAVING NO EXTERNAL ANTENNA JACK</b></div><div><br /></div><div>For the MW broadcast band, feeding the LoG or any low noise antenna to a pocket or portable radio is easy. I find inductive coupling best.</div><div><br /></div><div>Salvage a short ferrite rod or bar from an old pocket radio. Three inches in length is about right. Remove all the magnet wire from it. Using some solid, insulated telephone wire of about 24-26 gauge, wind about 15-20 turns close-wound around the ferrite rod. Solder or clip the two ends of wire from this coil to the coax feeder coming from the antenna, one to the center and one to the shield. Hold the ferrite close to the radio's internal ferrite which will inductively-couple the signal to the radio. The advantage over a passive loop here is you have a broadband antenna which does not have to be tuned.</div><div><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggxAC_WbfQeVqR_eIQVo_Jjn-QIO6CpZVo4Wkm9pBneO232VZf2tOofsN_t2QzxYN16g8sFxHIY7PlTglXH-he7rn_popljnoLHYlA1dOgUflbEPbsftBSxlsob_FWUL5IKvtYoFG85sPr_8Pn_Onaqj3OJcfvDC4GpjAEnIzmAJ1uZnWPxwojuZDZPw/s450/loop_teaser.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="349" data-original-width="450" height="310" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggxAC_WbfQeVqR_eIQVo_Jjn-QIO6CpZVo4Wkm9pBneO232VZf2tOofsN_t2QzxYN16g8sFxHIY7PlTglXH-he7rn_popljnoLHYlA1dOgUflbEPbsftBSxlsob_FWUL5IKvtYoFG85sPr_8Pn_Onaqj3OJcfvDC4GpjAEnIzmAJ1uZnWPxwojuZDZPw/w400-h310/loop_teaser.jpg" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Ferrite coupling</td></tr></tbody></table><br /><div><div><b>ADDITIONAL READING</b></div><div><b><br /></b></div><div>Fabricating Impedance Transformers for Receiving Antennas, by John Bryant:</div><div><br /></div><div><a href="https://www.qsl.net/wa1ion/doc1/z_transformers.pdf">https://www.qsl.net/wa1ion/doc1/z_transformers.pdf</a></div><div><br /></div><div>Broadband Receiving Antenna Matching, by Mark Connelley, WA1ION:</div><div><br /></div><div><a href="https://www.qsl.net/wa1ion/bev/bb_antenna_matching.pdf">https://www.qsl.net/wa1ion/bev/bb_antenna_matching.pdf</a></div><div><br /></div><div><b>WRAP UP</b></div><div><br /></div><div>I would encourage many of you with RFI problems to try the Loop-on-Ground antenna. Don't dismiss it just because it lies on the ground. Cut to the right size, the LoG can be effective anywhere from longwave to 30 MHz. Experiment!</div></div><div><br /></div></div>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com15tag:blogger.com,1999:blog-4260200412608523752.post-26917331203507112862022-02-04T06:04:00.002-05:002022-02-04T14:40:00.515-05:00Working Jean Shepherd<div>Jean Parker Shepherd, Jr. (1921-1999), often referred to by the nickname Shep, was an American storyteller, humorist, radio and TV personality, writer, and actor. With a career that spanned decades, Jean was best known for the film A Christmas Story (1983), which he narrated and co-scripted. It was based on stories from his youth, growing up in Hammond, Indiana, in the 1930s.</div><div><br /></div><div>Perhaps lesser known, Jean was a lifelong radio enthusiast and ham operator. In his middle years, he regaled his nightly WOR-710 radio audience with quirky social commentary, stories of post-depression life, of early radio, and his Army years.</div><div><br /></div><div>I grew up listening to the Jean Shepherd radio show from about 1960 till 1966 when I went into the service. His show was carried by WOR-710 in New York. It was on every night, Monday to Friday, from 10 PM till 11. I was a kid and lived in the Philadelphia area, only 90 miles from NYC. I would lie in bed cuddled up to a 5 tube superhet and then later a transistor radio. In between I would DX. Wolfman Jack would boom in from the Texas/Mexico border.</div><div><br /></div><div>I got my ham license in 1963, and Jean's previous night's monolog was always the talk of the high school radio club every day. He was idolized among the young ham radio crowd because Jean was also a ham. His call was K2ORS.</div><div><br /></div><div>I had the privilege of working Jean on 15 meter SSB one day in the early 1980s. I was out of the service and married and lived in the Denver, Colorado area. My call was W0OHF at the time. The band was seemingly dead. I called CQ and this voice came back: "W0OHF, this is K2ORS". It took a few seconds to register. I hadn't thought of Jean in quite a few years. Could it be??</div><div><br /></div><div>It indeed was. He was in Ft. Lauderdale, Florida, enjoying a respite of sorts. He was operating portable from the top floor of a condo building with a short stick vertical clamped to the porch railing. We chatted for 45 minutes.</div><div><br /></div><div>I related the story of my youth to him and how much his radio shows meant to me as a teenager. And I thanked him for that. It was one of the greatest thrills of my radio-life.</div><div><br /></div><div>His stories of early radio and Army life set the stage for my own life. He was one of my heroes.</div><div><br /></div><div>If you remember the famed "brass figlagee with bronze oak-leaf palm" or "watch out for live wires", you know of Jean Shepherd.</div><div><br /></div><div>In 2005, Shepherd was posthumously inducted into the National Radio Hall of Fame.</div><div><br /></div><div>"Excelsior, you fathead!!!", he would exclaim.</div><div><br /></div><div>Thank you, Shep, for all the wonderful memories.</div><div><br /></div><div>Bill, WE7W</div><div><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEgs6kTERIOdzdoTw2Yn2-F6J8xGVjhWedNFql0crLTCPSIyV0EEdI17zt4zdvAWgiy9ebfv2hR5_iUXSHJBweKZfV01m8TOBLmoGuii5Rb-F9aSyIp1O489vlodE_zoW6tpNcBQ1dSW1GT54hqvCxedTpJpCapcal_DLCHoGA5Cb2yF-mw1Jeh1D3XLhw=s500" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="453" data-original-width="500" height="290" src="https://blogger.googleusercontent.com/img/a/AVvXsEgs6kTERIOdzdoTw2Yn2-F6J8xGVjhWedNFql0crLTCPSIyV0EEdI17zt4zdvAWgiy9ebfv2hR5_iUXSHJBweKZfV01m8TOBLmoGuii5Rb-F9aSyIp1O489vlodE_zoW6tpNcBQ1dSW1GT54hqvCxedTpJpCapcal_DLCHoGA5Cb2yF-mw1Jeh1D3XLhw=s320" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><span style="text-align: left;">Jean Shepherd, 1921-1999</span></td></tr></tbody></table><br /><div><br /></div>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com3tag:blogger.com,1999:blog-4260200412608523752.post-30961853438511720422022-01-15T17:24:00.006-05:002022-01-15T17:37:04.140-05:00Canadian Graveyard Stations<p>
The other day I stripped off the official list of Canadian graveyard stations,
per Industry Canada. Taken from their database of Dec. 21, 2021. All of these
still show licensed by IC. One or more of the lower power ones may be
inactive. TIS stations? The database doesn't indicate it.
</p>
<p>
<span style="font-family: courier;"
>Call Frequency Power Location</span
>
</p>
<p>
<span style="font-family: courier;"
>---- --------- ----- ----------------</span
>
</p>
<p>
<span style="font-family: courier;"
>CBPD 1230 5
Glacier Park, BC</span
>
</p>
<p>
<span style="font-family: courier;"
>CHFC 1230 250
Churchill, MB </span
>
</p>
<p>
<span style="font-family: courier;"
>CFNI 1240 1000 Port
Hardy, BC </span
>
</p>
<p>
<span style="font-family: courier;"
>CJOR 1240 1000 Osoyoos,
BC </span
>
</p>
<p>
<span style="font-family: courier;"
>CKMK 1240 1000
Mackenzie, BC </span
>
</p>
<p>
<span style="font-family: courier;"
>CJAR 1240 1000 The Pas,
MB </span
>
</p>
<p>
<span style="font-family: courier;"
>CKIM 1240 1000 Baie
Verte, NF </span
>
</p>
<p>
<span style="font-family: courier;"
>CBLE 1240 40
Beardmore, ON </span
>
</p>
<p>
<span style="font-family: courier;"
>CBLO 1240 40
Mattawa, ON </span
>
</p>
<p>
<span style="font-family: courier;"
>CINL 1340 1000 Ashcroft,
BC </span
>
</p>
<p>
<span style="font-family: courier;"
>CJEV 1340 50
Elkford, BC </span
>
</p>
<p>
<span style="font-family: courier;"
>CFKC 1340 250 Creston,
BC </span
>
</p>
<p>
<span style="font-family: courier;"
>CBLB 1340 40
Schreiber, ON </span
>
</p>
<p>
<span style="font-family: courier;"
>CHNL 1400 1000
Clearwater, BC </span
>
</p>
<p>
<span style="font-family: courier;"
>CIOR 1400 1000
Princeton, BC </span
>
</p>
<p>
<span style="font-family: courier;"
>CBG 1400 4000
Gander, NF </span
>
</p>
<p>
<span style="font-family: courier;"
>CBOF 1400 40
Rolphton, ON </span
>
</p>
<p>
<span style="font-family: courier;"
>CBMD 1400 40
Chapais, QC </span
>
</p>
<p>
<span style="font-family: courier;"
>CBKA 1450 40
Stewart, BC </span
>
</p>
<p>
<span style="font-family: courier;"
>CFAB 1450 1000 Windsor,
NS </span
>
</p>
<p>
<span style="font-family: courier;"
>CBLF 1450 40
Foleyet, ON </span
>
</p>
<p>
<span style="font-family: courier;"
>CHOU 1450 2000 Montréal,
QC </span
>
</p>
<p>
<span style="font-family: courier;"
>CBPC 1490 5
Glacier Park, BC </span
>
</p>
<p>
<span style="font-family: courier;"
>CFNC 1490 50
Cross Lake, MB </span
>
</p>
<p>
<span style="font-family: courier;"
>CHTO 1490 23
Mississauga, ON </span
>
</p>
<p>
<span style="font-family: courier;"
>CBPP 1490 20
Prince Edward Island, PE </span
>
</p>
<p>
<span style="font-family: courier;"
>CJSN 1490 1000
Shaunavon, SK</span
>
</p>
<p>
<span style="font-family: courier;"><br /></span>
</p>
RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com0tag:blogger.com,1999:blog-4260200412608523752.post-937543124753389872022-01-14T05:45:00.005-05:002022-02-04T14:44:22.995-05:00Visiting Barry Goldwater<p>Remember Barry Goldwater, K7UGA? Yes, that Barry Goldwater, the senator who ran for president against Lyndon Johnson in 1964. Barry was a ham operator.</p><p>When I was a kid in 1964, the year Goldwater ran for president, my high school friend Jeff and I took the afternoon off from school and went to the local W.T.Grants store parking lot and watched him speak during a campaign sweep through Warminster, PA. I was thrilled. Of course, all my other ham buddies were there to cheer him on. There wasn't a teenaged ham who wasn't for Barry.</p><p>In 1987 I moved to Phoenix, Arizona, where I spent a couple of years before moving on to smaller digs. Now, many know that Goldwater was from Arizona, and specifically from Phoenix. I remembered one time when I was a kid seeing a picture of his house in QST magazine. It was the perfect DX location, high on a mountain overlooking the city, with a huge antenna array on a tall tower. Barry was quite active in the amateur MARS service too and ran many phone patches for GIs overseas, especially during the Vietnam era. I decided it shouldn't be too hard to find that house, if he was still in the same one.</p><p>So, one day I was running around in my car and found myself in north Phoenix. Now in north Phoenix, there are several little conical shaped mountains. Understand too that there was housing all around them, even on the tops of these things. So, I started looking around. Sure enough, on the highest one right off of Lincoln Ave. stood a huge antenna tower and array. Something came over me and I thought - what the hell - I'll drive up there and see what happens. So, I did.</p><p>I snaked up this road, past lesser housing, and found myself at the top of this small mountain at the entrance to a large, gated property and 1950s style house. There in front of me was the huge antenna array. I just knew this had to be Goldwater's house. The gate was open, so....</p><p>I drove in and parked by the garage, which was separate from the house, but connected through a covered walkway. Well, I had come this far and not gotten arrested, so I walked up to the front door and knocked. An elderly woman came to the door. In my most innocent voice, I identified myself, told her I was a ham, and asked if Mr. Goldwater was in. She replied she was the housekeeper and that no, Mr. Goldwater was in Washington on business. She then asked me if I would like to see the station!!! I about wet my pants, and of course I said YES!!! She took me into the garage, which Barry had remodeled into a first-class ham station, all in cherry wood paneling. The entire thing was expensive Collins equipment. All of it!!!! All set into a custom-made desk/wall in the middle of the room. On the outer walls were dozens of 8x10 pictures of Barry with every leader of the world you can think of, from Nikita Khrushchev of the USSR, King Hussein of Jordan, to Kennedy, to Nixon, and Eisenhower on down. In front of the huge radio desk/wall was a giant coffee table with a glass cover. In that coffee table were keys to the cities of the world. There had to have been two dozen of them in there. What an experience!</p><p>The housekeeper let me wander around and look at everything. When I was done, I said thank you and goodbye and drove back down the mountain, flying about 100 feet off the road. I had been to Barry Goldwater's house and had been given the tour!!</p><p>Thought you might like this story. People have told me that it took balls to do that. But to me it seemed like one ham visiting another. I'm sure if Barry had been home, he would have given me the tour, just the same. Hams are like that.</p><p>Bill WE7W</p><p><br /></p>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com2tag:blogger.com,1999:blog-4260200412608523752.post-64904846787436610242021-10-25T14:02:00.009-04:002021-10-25T14:30:18.314-04:00RDMW 2022 Mediumwave Pattern Reference<p><span face="Montserrat, sans-serif" style="background-color: white; color: #000f2b; letter-spacing: 2.5px;"><span style="font-size: medium;"><b>North American Broadcast Mapping Tool & Database</b></span></span></p><p style="background-color: white; border: 0px; box-sizing: inherit; color: #625f5f; font-family: Montserrat, sans-serif; font-size: 16px; margin: 0px 0px 1.6em; outline: 0px; padding: 0px; vertical-align: baseline;">We are proud to announce the launch of the latest edition RDMW-2022 Medium Wave Pattern Reference. Now in its 9th year, RDMW comes with many new features and updated station data ready for 2022.</p><p style="background-color: white; border: 0px; box-sizing: inherit; color: #625f5f; font-family: Montserrat, sans-serif; font-size: 16px; margin: 0px 0px 1.6em; outline: 0px; padding: 0px; vertical-align: baseline;">Radio Data Medium Wave (RDMW) allows you to see and map the coverage area of all medium wave (AM/MW) broadcast stations in North America.</p><p style="background-color: white; border: 0px; box-sizing: inherit; color: #625f5f; font-family: Montserrat, sans-serif; font-size: 16px; margin: 0px 0px 1.6em; outline: 0px; padding: 0px; vertical-align: baseline;">Included is a complete set of Google Map-based, HTML-driven maps which show the most current pattern plots of all licensed US and Canadian mediumwave broadcast stations from 530 - 1700 KHz. Through careful curating, virtually 99% of all licensed Mexican stations are also included, the vast majority with plots. Lastly, also included are a sample of Caribbean stations, and the coastal marine NAVTEX 490 Khz and 518 KHz stations.</p><p style="background-color: white; border: 0px; box-sizing: inherit; color: #625f5f; font-family: Montserrat, sans-serif; font-size: 16px; margin: 0px 0px 1.6em; outline: 0px; padding: 0px; vertical-align: baseline;">The set includes all frequencies for the indicated services: Unlimited, Daytime, Nighttime, and Critical Hours. Data for the plots is based on the current FCC and Industry Canada databases available at creation (October 19, 2021).</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-MCs_FlMq5MM/YXahfKQtP8I/AAAAAAAADNs/6gf8n7sDzb42Wpi9eOMa6prknYEJlCLFgCLcBGAsYHQ/s901/870kHz-rar-traced-to-York-Uk.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="573" data-original-width="901" height="408" src="https://1.bp.blogspot.com/-MCs_FlMq5MM/YXahfKQtP8I/AAAAAAAADNs/6gf8n7sDzb42Wpi9eOMa6prknYEJlCLFgCLcBGAsYHQ/w640-h408/870kHz-rar-traced-to-York-Uk.jpg" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">870 KHz - skywave at night to the UK</td></tr></tbody></table><p>If you've ever wondered why a radio listener would be interested in the coverage patterns or maps of radio stations then <a href="https://mwcircle.org/north-american-mw-coverage-maps/" target="_blank">you can find out at Medium Wave Circle</a>.</p><p style="background-color: white; border: 0px; box-sizing: inherit; color: #625f5f; font-family: Montserrat, sans-serif; font-size: 16px; margin: 0px 0px 1.6em; outline: 0px; padding: 0px; vertical-align: baseline;">New developments for 2022 include:</p><ul style="background-color: white; border: 0px; box-sizing: inherit; color: #625f5f; font-family: Montserrat, sans-serif; font-size: 16px; list-style-image: initial; list-style-position: initial; margin: 0px 0px 1.5em 3em; outline: 0px; padding: 0px; vertical-align: baseline;"><li style="border: 0px; box-sizing: inherit; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">The latest callsign and technical data for all US and Canadian MW stations</li><li style="border: 0px; box-sizing: inherit; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Expansion to cover Mexico, Bahamas and the Caribbean for the first time</li><li style="border: 0px; box-sizing: inherit; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Expansion to cover 490kHz – 1700kHz; now includes MW Navtex stations</li><li style="border: 0px; box-sizing: inherit; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Addition of real-time night/day terminator (greyline)</li><li style="border: 0px; box-sizing: inherit; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">“Click+Save” setting of your receiver location</li><li style="border: 0px; box-sizing: inherit; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Easy tuning control added to control bar</li><li style="border: 0px; box-sizing: inherit; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Easy daypart selector added to control bar</li><li style="border: 0px; box-sizing: inherit; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Ray tracing control added on a per station basis.</li><li style="border: 0px; box-sizing: inherit; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">In-screen “Help” button</li></ul><p style="background-color: white; border: 0px; box-sizing: inherit; color: #625f5f; font-family: Montserrat, sans-serif; font-size: 16px; margin: 0px 0px 1.6em; outline: 0px; padding: 0px; vertical-align: baseline;">Knowledge drawn from RDMW has been fundamental in helping DXers further their craft and enjoy their hobby. It can help you plan your listening and help you target stations broadcasting from particular areas. Intelligence displayed by RDMW has helped U.S. & European DXers plan and hear US stations over great distances – including so-called “daytimer DX” and transpolar propagation. The RDMW maps will also help you determine which stations you might hear on a particular channel, and which might be rather more elusive.</p><p style="background-color: white; border: 0px; box-sizing: inherit; color: #625f5f; font-family: Montserrat, sans-serif; font-size: 16px; margin: 0px 0px 1.6em; outline: 0px; padding: 0px; vertical-align: baseline;">Drawing on the latest data from official sources, club sources and topped off with many days of extensive data checking and validation RDMW probably has the most comprehensive and up to date dataset for AM/MW broadcasting stations in North America. This data is combined with complex geophysical data and propagation modelling to provide you with extremely detailed coverage maps for both daytime groundwave and nighttime skywave coverage for around 5000 radio stations.</p><p style="background-color: white; border: 0px; box-sizing: inherit; color: #625f5f; font-family: Montserrat, sans-serif; font-size: 16px; margin: 0px 0px 1.6em; outline: 0px; padding: 0px; vertical-align: baseline;">RDMW 2022 has been developed and tested by Bill Scott and Steve Whitt and is exclusively available from the Medium Wave Circle DXing club.</p><p style="background-color: white; border: 0px; box-sizing: inherit; color: #625f5f; font-family: Montserrat, sans-serif; font-size: 16px; margin: 0px 0px 1.6em; outline: 0px; padding: 0px; vertical-align: baseline;">This year marks a sea change in how the map sets will be delivered to you, the end user. Europe's premier medium wave DX club, <a href="https://mwcircle.org/">The Medium Wave Circle</a> will be hosting the download. The Medium Wave Circle is an international club for radio enthusiasts. It brings together people all over the world with a similar interest in medium wave radio (MW, AM or BCB) and related topics.</p><p style="background-color: white; border: 0px; box-sizing: inherit; color: #625f5f; font-family: Montserrat, sans-serif; font-size: 16px; margin: 0px 0px 1.6em; outline: 0px; padding: 0px; vertical-align: baseline;">A small fee will be charged to cover bandwidth costs, less than a price of a coffee. Paid membership in the club is not required. Payment is through a PayPal gateway and is safe and secure. You do not need a PayPal account to use this facility.</p><p style="background-color: white; border: 0px; box-sizing: inherit; color: #625f5f; font-family: Montserrat, sans-serif; font-size: 16px; margin: 0px 0px 1.6em; outline: 0px; padding: 0px; vertical-align: baseline;">Click the link just below and get your copy today.</p><p style="background-color: white; border: 0px; box-sizing: inherit; color: #625f5f; font-family: Montserrat, sans-serif; font-size: 16px; margin: 0px 0px 1.6em; outline: 0px; padding: 0px; vertical-align: baseline;"><a href="https://mwcircle.org/radio-data-mw-rdmw-2022/">RDMW 2022 Medium Wave Pattern Reference – Medium Wave Circle (mwcircle.org)</a></p><p style="background-color: white; border: 0px; box-sizing: inherit; margin: 0px 0px 1.6em; outline: 0px; padding: 0px; vertical-align: baseline;"><span face="Montserrat, sans-serif" style="color: #625f5f; font-size: 16px;">Consider supporting The Medium Wave Circle by joining. Its membership fee is a modest amount for a great return. You will also get access to the group's monthly newsletter, The Medium Wave News, published since 1954, and over 500 past copies of MWN available exclusively to members. You will also get access to the Circle archives and pre-publication discounts on the essential reference book the World Radio TV Handbook. Last but not least, you will have access to a great forum of friendly and helpful people on groups.io.</span></p><p style="background-color: white; border: 0px; box-sizing: inherit; color: #625f5f; font-family: Montserrat, sans-serif; font-size: 16px; margin: 0px 0px 1.6em; outline: 0px; padding: 0px; vertical-align: baseline;">We hope you will enjoy this latest version of the Radio Data Medium Wave Pattern Reference. Several hundred hours have been spent this year enhancing the pattern generating program and curating the data. Best of DX!</p><p style="background-color: white; border: 0px; box-sizing: inherit; color: #625f5f; font-family: Montserrat, sans-serif; font-size: 16px; margin: 0px 0px 1.6em; outline: 0px; padding: 0px; vertical-align: baseline;"><br /></p>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com0tag:blogger.com,1999:blog-4260200412608523752.post-50789506264518635622021-10-05T03:41:00.004-04:002022-05-06T04:09:11.127-04:00Magnetic Longwire Balun : The Original by RF Systems<p> An oldie but a goodie. Remember this?</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-MW9R1WncCkA/YVv7vCLHU6I/AAAAAAAADMY/DBbJEUswrTc9IK0gEE3oXgt9UuGml6XGgCLcBGAsYHQ/s350/rf-systems_balun_2.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="350" data-original-width="297" height="320" src="https://1.bp.blogspot.com/-MW9R1WncCkA/YVv7vCLHU6I/AAAAAAAADMY/DBbJEUswrTc9IK0gEE3oXgt9UuGml6XGgCLcBGAsYHQ/s320/rf-systems_balun_2.jpg" width="272" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Magnetic Longwire Balun</td></tr></tbody></table><p>Years ago (almost 40) when I was quite active in my ham career and shortwave DXing I purchased one of these for about $40. An expensive little device. But I was curious about the claims.</p><p>It was advertised as a magnetic balun, low noise, matching almost anything below 40 MHz. Receive only of course. You can search on "RF Systems Magnetic Balun" and find many sites, blogs and forums where the merits of this device have been discussed.</p><p>The RF Systems Magnetic Balun is basically an 18:1 impedance matching transformer. "Balun" means balanced-to-unbalanced transformation - a transformer device which takes a balanced impedance (like the center feed point off a dipole) and transforms it to an unbalanced impedance (like coaxial cable). The RF Systems Magnetic Balun is really not a balun but what is known as an Un-un. In this case, an 18:1 impedance transformer, transforming an unbalanced input to an unbalanced output. One such example might be to match the unbalanced end-fed longwire to a 50 ohm coaxial cable, which is also unbalanced.</p><p>In more recent times, I've had very good luck with mine using it with both a "longwire" and a 25 ft., ground-mounted, but ungrounded vertical. Longwire in this case, means anything of 25 to 100 ft. in length, which is not really long in the traditional sense.</p><p>In personal experience over the years, the low noise claim gave minimal results. Low noise might be gained by positioning your longwire a ways away from any noise source and feeding the receiver with a long run of coax. But that's just common sense. Grounding the coax's shield at the entry point to the house can help too.</p><p>Presented at the bottom of this post are good quality .JPG images of the original document which came with the RF Systems Magnetic Balun.</p><p><br /></p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyewbGyU4yIjrI7iuxuNE64ocn8CCys40WEPW3ETcEsGeYhcMUaGasbZjQuwivD8LULxvJuFa3R5KCdW5jS9CJj9lb4F358TUWRmTvB02LQcEzC8xtjPvMylb_2nLXqclfEpUNT918gA-GMQffG0AR6iCXQ9XLcub9V7OA3iZihMsJpzz1NdoaVkWbrA/s860/mlb_ad.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="806" data-original-width="860" height="375" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyewbGyU4yIjrI7iuxuNE64ocn8CCys40WEPW3ETcEsGeYhcMUaGasbZjQuwivD8LULxvJuFa3R5KCdW5jS9CJj9lb4F358TUWRmTvB02LQcEzC8xtjPvMylb_2nLXqclfEpUNT918gA-GMQffG0AR6iCXQ9XLcub9V7OA3iZihMsJpzz1NdoaVkWbrA/w400-h375/mlb_ad.jpg" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">jbe.nl catalog item for the RF Systems Magnetic Balun</td></tr></tbody></table><p><b><br /></b></p><p><b>Other Matching Options</b></p><p>Good or even better results can sometimes be had with other matching devices like an antenna tuner which will also do the matching like a balun would. <a href="https://mfjenterprises.com/">MFJ Enterprises</a> has quite a few which can be used for simply tuning odd lengths of wire. Google will produce many results for antenna tuners. They can be made pretty simply with a variable capacitor and some hand wound coils.</p><p>For AM broadcast DXing I prefer inductive coupling right into the radio's own ferrite antenna. Matching is pretty well taken care of then and good signal transfer is also accomplished, and often without the overloading that can occur when directly connected.</p><p>A circuit example of a similar, but 9:1 impedance transformation "magnetic balun" can be found at <a href="https://m0ukd.com/homebrew/baluns-and-ununs/91-magnetic-longwire-balun-unun/">M0UKD</a>.</p><p>This is another "un-un", as it transforms between unbalanced input (the longwire) to unbalanced output (the coax input of the radio). This circuit is actually the same circuit as the RF Systems balun I have. It takes a high impedance (the longwire) and transforms it by a 9:1 ratio down to a lower impedance (usually the radio's input connector). Note that radios with external longwire posts like a CCRadio SW may already be set up for high impedance input. It depends on the input circuitry used in the radio.</p><p>Be careful directly connecting wire to any of these DSP radios. Modern chip electronics is not so forgiving as the old tube stuff from my generation. I have fried several radios with static discharge.</p><p>Inductive coupling to a radio's ferrite loop can easily be done.</p><p>Find an old piece of ferrite bar or rod and close-wind 15-20 turns of insulated wire on it. Ground one end to the earth and connect the other end to the longwire. Then couple the ferrite bar/rod to your radio's ferrite antenna. You can even run it through a length of coaxial cable, though better results will be obtained by using the RF Systems balun or 9:1 balun where the longwire connects to the end of the coax (outside).</p><p>My 25 ft. vertical is set up that way. Picture the vertical as a simple end fed longwire (fed at the bottom and insulated from the ground). It is attached there to the RF Systems balun and through the balun to the coaxial cable. The 50 ft. coax cable runs to the inside of the house where the center and shield of the coax is connected to the 15-20 turn winding around that spare piece of ferrite bar/rod.</p><p>Sensitivity can then be adjusted by the closeness of the coupling to the radio.</p><p>Be aware, most of these radios are easily overloaded by excessive signal. It shouldn't take much of a longwire to do that.</p><p>The old-fashioned Pi type tuners work quite well for longwires. This involves two variable capacitors with a coil between them. I used to have a homemade one which I used for years on the ham bands for both transmit and receive. That style can match about anything.</p><p><b>The Grove TUN-4 Antenna Tuner</b></p><p>Grove Electronics, now out of business, (they also published the Monitoring Times magazine years ago) used to sell quite a few receive tuners. I still have the TUN-4 which is quite nice and will tune from below the AM band to 30 MHz. It also has a preamplifier. You can often find these and the others on eBay. The <a href="https://www.americanradiohistory.com/">American Radio History</a> web site has many old radio catalogs which you can peruse. Here is an old Grove catalog, dating back to 1989.</p><p><a href="https://www.americanradiohistory.com/Archive-Monitoring-TImes/Grove-Catalog/Grove-1989-02.pdf">Grove Catalog, 1989</a></p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-25VdaD2RD1A/YVv_LydiooI/AAAAAAAADMg/Zvs_9Y-s8IcaQWSCZtK6_JgviL19an-lwCLcBGAsYHQ/s400/grove-model-tun-4.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="264" data-original-width="400" height="264" src="https://1.bp.blogspot.com/-25VdaD2RD1A/YVv_LydiooI/AAAAAAAADMg/Zvs_9Y-s8IcaQWSCZtK6_JgviL19an-lwCLcBGAsYHQ/w400-h264/grove-model-tun-4.jpg" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">The Grove TUN-4 Antenna Tuner</td></tr></tbody></table><p>Why impedance matching?</p><p>Maximum signal is transferred (and I might add with minimum distortion) if the impedance is matched between input and output of a circuit. To give a simple example, in the old days of Hi-Fi the audio enthusiast always made sure his speakers were matched to the stereo's speaker output. If the stereo had an 8 ohm speaker connection, you made sure you used 8 ohm speakers, not 16 or 32 ohm speakers. Maximum signal would be transferred to an 8 ohm speaker, and also as important, minimum distortion would result.</p><p>The same is with radio and antennas. Typical longwire antennas might have an inherent impedance in the neighborhood of 450 ohms, or more. Old radios which had a single antenna post for a longwire usually made sure that the input was designed around 450 ohms. The coax inputs or mini-jack inputs of most receivers are usually designed around an input impedance of about 50 ohms. If we connect a longwire to one of these inputs we are creating a series circuit of 450+50 or 500 ohms at the input with our "tap" at the 50 ohm point above ground. Ohm's law tells us that we are only getting 50/500 or one-tenth the signal available from the longwire. This is remedied by the impedance matching transformer or by the antenna tuner. Properly matched, we get the full signal off the longwire.</p><p>In the ham radio world, good matching is even more important when transmitting to an antenna. A poor match results in the antenna reflecting some or most of the power right back at the transmitter. These reflections also exist on receiving antennas when mis-matched.</p><p>Some radios seem to be a little more tolerant of antenna mismatch, some not. I have the SDRPlay RSP1a SDR receiver here and I find it not tolerant at all of antenna mis-match. Another, the Yaesu FRG-7, dating back to the late 1970s, is particularly sensitive to proper impedance matching. This is a very sensitive radio, but you must match the antenna to it to get maximum results, and particularly on mediumwave. Many radios, however, will respond favorably by hooking up any sort of wire to them.</p><p>For receive purposes, feeding the radio using 75 ohm coax instead of 50 ohm won't matter much. I've used 75 ohm TV cable for years for receiving on the HF bands - 30 MHz and below. Transmitting or VHF/UHF work would be a different story. The 75 ohm to 50 ohm mis-match is a 1.5:1 mis-match, which coincidentally is also a 1.5:1 SWR (Standing Wave Ratio) in the ham radio transmitting world. That's usually about at the edge of acceptability for transmitting in the HF range.</p><p>The impedance transformation of 450 to 50 ohms is a 9:1 ratio of course. It is based on the windings ratio and is equivalent to the square of the windings ratio. If the input side (the 450 ohm side) has 3 times the number of turns than the output side (the 50 ohm side), then the turns (windings) ratio is 3. 3 squared = 9, so the impedance transformation is 9:1. The RF Systems balun, at 18:1, presents a turns ration of about 4.25, the square root of 18.</p><p>For 75 ohms, you'd need an impedance transformation ratio of 6:1 (450/75). The square root of 6 is approximately 2.5, so you'd need a turns ratio of 2.5 from input to output. 10 turns to 4 turns would do it.</p><p>Understand that the 450 ohm figure for the longwire may vary greatly above or below this figure depending on the frequency you are receiving. In other words, the impedance presented at the end of the wire is frequency dependent. The original concept of a longwire was a wire of several wavelengths. Casually, someone throws an odd length of wire out a window and calls it a longwire. If your end-fed "longwire" is anywhere near one-quarter wavelength of the frequency being received, you probably are looking at an impedance of 20-75 ohms, not 450 ohms. An end-fed halfwave length of wire might present itself around 1000-2000 ohms. The point I'm trying to make here is that the 9:1 or 18:1 balun is there just to get you in the ballpark for this higher impedance, matching-wise.</p><p>And now, the RF Systems Magnetic Balun. Click on each image for the full resolution.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-b_8-sUDatlE/YVv6swz-KoI/AAAAAAAADL4/x9p_DUM3_CwrNhFbvbHC4qGoola6-WNyQCLcBGAsYHQ/s1687/0001%252B1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1687" data-original-width="1024" height="640" src="https://1.bp.blogspot.com/-b_8-sUDatlE/YVv6swz-KoI/AAAAAAAADL4/x9p_DUM3_CwrNhFbvbHC4qGoola6-WNyQCLcBGAsYHQ/w388-h640/0001%252B1.jpg" width="388" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-fmBunGuEYLY/YVv7QcqTyJI/AAAAAAAADMA/nANU0EJoTjwgoeKQAGDWzyNYkE_Gn94yACLcBGAsYHQ/s1687/0002%252B1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1687" data-original-width="1024" height="640" src="https://1.bp.blogspot.com/-fmBunGuEYLY/YVv7QcqTyJI/AAAAAAAADMA/nANU0EJoTjwgoeKQAGDWzyNYkE_Gn94yACLcBGAsYHQ/w388-h640/0002%252B1.jpg" width="388" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-broprD_AViw/YVv7W1xJgYI/AAAAAAAADME/QNn9J15R5r8u0su476lFA8dFQ4VQoGBFwCLcBGAsYHQ/s1687/0003%252B1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1687" data-original-width="1024" height="640" src="https://1.bp.blogspot.com/-broprD_AViw/YVv7W1xJgYI/AAAAAAAADME/QNn9J15R5r8u0su476lFA8dFQ4VQoGBFwCLcBGAsYHQ/w388-h640/0003%252B1.jpg" width="388" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-3IC7bbDk2j8/YVv7dqouzRI/AAAAAAAADMI/zOSkH-SzZYgs5GVkI_Jp4h0tiHQ-Ygd-QCLcBGAsYHQ/s1687/0004%252B1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1687" data-original-width="1024" height="640" src="https://1.bp.blogspot.com/-3IC7bbDk2j8/YVv7dqouzRI/AAAAAAAADMI/zOSkH-SzZYgs5GVkI_Jp4h0tiHQ-Ygd-QCLcBGAsYHQ/w388-h640/0004%252B1.jpg" width="388" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><br /></div><br /><div class="separator" style="clear: both; text-align: center;"><br /></div><br /><div class="separator" style="clear: both; text-align: center;"><br /></div><br /><p><br /></p>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com1tag:blogger.com,1999:blog-4260200412608523752.post-626036875686145672021-09-26T05:05:00.000-04:002021-09-26T05:05:00.840-04:00Greyline Propagation<p>Let's talk about greyline propagation.</p><p>Greyline propagation, or propagation along the earth's sunrise/sunset terminator, is very noticeable on the 160, 80, and 40 meter ham bands and lower shortwave bands. Mediumwave signals can and do travel that path as well.</p><p>What does the greyline look like on a map?</p><p>There's a great solar clock map I've found which I use called Simon's World Map. You can start it and leave it on your desktop.</p><p><a href="https://www.dit-dit-dit.com/world-map">Simon's World Map</a></p><p>It's freeware. The creator (Simon) is the guy involved in the HF+ Discovery SDR project, competitors to the SDRPlay and SDRUno, and others.</p><p>A screenshot of mine in use right now:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-HcnUYXJJoR8/YVAz5xAfmfI/AAAAAAAADLA/p-MIAwqSF64U4GJ9-7Wtd3HYLxyKbYQTgCLcBGAsYHQ/s990/simons_map.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="644" data-original-width="990" height="260" src="https://1.bp.blogspot.com/-HcnUYXJJoR8/YVAz5xAfmfI/AAAAAAAADLA/p-MIAwqSF64U4GJ9-7Wtd3HYLxyKbYQTgCLcBGAsYHQ/w400-h260/simons_map.jpg" width="400" /></a></div><p>The night/day overlay over the world map shows the width of the earth's terminator and its transition from total darkness to the sunrise and sunset edge. The actual sunrise or sunset point is the edge where the overlay disappears. The lightest band of the overlay is civil twilight, where the sun is just below the horizon to a point 6 degrees below the horizon. The next darkest band is nautical twilight, where the sun is between 6 degrees and 12 degrees below the horizon. The next darkest band is astronomical twilight, where the sun is between 12 degrees and 18 degrees below the horizon. The darkest area is where total darkness exists, where the sun's position is greater than 18 degrees below the horizon. Medium wave and other signals in the lower shortwave bands, as described above, can propagate along the terminator at greatly reduced signal attenuation - often received at astonishing distances. </p><p>Space Weather Specialists define it this way on their Real-Time Maximum MUF page, found here:</p><p><a href="http://www.spacew.com/www/realtime.php">Space Weather Specialists</a></p><p>Their definition puts the greyline stripe exactly between the rising or setting sun and the 12 degree point of darkness below the horizon, also known as the Nautical Twilight point. However, they seem to ignore any greyline existence on the daylight side of SR/SS.</p><p>Civil twilight is halfway to Nautical Twilight, or 6 degrees below the horizon.</p><p>Published sunrise/sunset times in newspapers and charts almost always base their times on "Official" sunrise/sunset which is 90 degrees 50 minutes, or 90.833333 degrees from solar zenith, making their times several minutes different from actual SR/SS. Actual SR/SS is based on 90 degrees from solar zenith.</p><p>I would argue that greyline conditions of course exist for a time past sunrise and before sunset, straddling the actual SR/SS. How much? I would tend to split it at about 6-9 degrees on either side of SR/SS, but it depends on the frequency too. 6 degrees rotation of the earth is 24 minutes of clock time.</p><p>12 degrees below the horizon seems a bit much to me. 12 degrees of earth curvature is 828 miles or 48 minutes of sun travel which is quite a departure from actual sunrise and sunset. Again, I would tend to split it at 6-9 degrees on either side of SR/SS. 7.5 degrees is 30 minutes, which seems about right.</p><p>VOACAP has a nice calculator which gives their representation of greyline start and end times by location and date:</p><p><a href="https://www.voacap.com/greyline/index.html">VOACAP Calculator</a></p><p>VOACAP uses the 6 degree below the horizon (darkness side) and 3 degree above the horizon (daylight side) points for their greyline calculations.</p><p>Their greyline notes can be read <a href="http://voacap.blogspot.com/2016/11/voacap-greyline-user-manual.html">here</a>.</p><p>My mediumwave broadcast pattern map set for 2022 is almost ready for publication, coming mid-October. This year it will be available exclusively on <a href="https://mwcircle.org/">The Medium Wave Circle</a>. Many changes and updates have been implemented over the last 18 months. One is a greyline day/night overlay, similar to Simon's World Map. Coming soon!</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-sDBtb6aNYjA/YVA29dZxYuI/AAAAAAAADLI/eTcO6H0Omt0yqaNLBoEiXv_pTdds5flagCLcBGAsYHQ/s838/rdmw_map.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="653" data-original-width="838" height="311" src="https://1.bp.blogspot.com/-sDBtb6aNYjA/YVA29dZxYuI/AAAAAAAADLI/eTcO6H0Omt0yqaNLBoEiXv_pTdds5flagCLcBGAsYHQ/w400-h311/rdmw_map.jpg" width="400" /></a></div><p>Greyline is a good topic for discussion. Maybe others have thoughts.</p><p>Bill</p>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com1tag:blogger.com,1999:blog-4260200412608523752.post-70430421666559933212021-08-27T02:47:00.002-04:002021-09-26T05:32:06.955-04:00A Radio Story<p>I had a conversation recently with a fellow who was interested in starting into the radio hobby, and I thought the conversation might be of interest to anyone who has ideas of radio DXing. I'll reproduce the gist of the conversation here.</p><p>Nice to meet you. Glad to see people are still getting involved in our "archaic" hobby!!</p><p>I'm 74 years old this year and have been involved since about 1960, some 60 years. I got my first ham license in 1963. Before that I used to listen on my grandfather's old Sears Silvertone wooden console as a young boy. Shortwave was fun in the days back then and in the 1970s, all during the Cold War. Fascinating and scary stuff.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-skv-xaCxj7k/YVA8e8x_YXI/AAAAAAAADLQ/X-ergmSvOkIwL8qxLM9YYQcGIJygCvkpgCLcBGAsYHQ/s400/silvertone-7067.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="400" data-original-width="291" height="400" src="https://1.bp.blogspot.com/-skv-xaCxj7k/YVA8e8x_YXI/AAAAAAAADLQ/X-ergmSvOkIwL8qxLM9YYQcGIJygCvkpgCLcBGAsYHQ/w291-h400/silvertone-7067.jpg" width="291" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Sears Silvertone 7067, about 1942</td></tr></tbody></table><p>I sort of quit the ham activity in the late 1990s after some 30 years, though I've hung on to that license. My ham and radio interest was always more of a technical one, though I made a lot of contacts all over the world via my preferred CW (code) mode over the years. Since about 2008 I've been doing a lot of mediumwave DXing mostly, but recently got back into shortwave listening too over the last couple of years.</p><p>International shortwave is only a fraction of what it was years ago. Most stations have moved on to the internet or don't exist at all. But don't be discouraged as there is still a lot of stuff out there to hear. It's just a little more difficult than the big booming signals of the old days.</p><p>I'm glad you decided to look for something beyond the Tecsun PL-380. It's 12 year old technology at this point and has been much improved since 2008 or so, even for those radios that are using the same radio chip. Silicon Labs makes the radio chips, though the Chinese have cloned them now and they produce their own too.</p><p>C Crane, a US company, also makes some nice radios, and sensitive too. Their original CC Skywave is actually sort of a "super" PL-380, but at about $80. The Chinese then cloned it with the RadiWow R-108, and in my opinion, did a better job for half the price. Understand, this is a tiny radio, it will fit in the palm of your hand. It is sensitive, and has corrected many of the original consumer gripes we had for the PL-380.</p><p><a href="https://ccrane.com/">https://ccrane.com/</a></p><p>I have a Tecsun PL-880. They are good radios with nice sound. It's more paperback book sized, where the PL-380 and R-108 are cigarette pack sized. On medium wave it's more sensitive with the longer ferrite antenna. Shortwave is a bit better too, and of course it can receive single sideband SSB as well. FM is superb of course. The only gripe I have with mine is the frequency readout is 2 KHz off on the AM band. An alignment problem I'm sure, but I don't think it's correctable at this point.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-4eAUjcYX6tY/YVA-B81-SXI/AAAAAAAADLY/n5rYR2Q_OhACwe7JO4VsFXl4-Ish_E7aQCLcBGAsYHQ/s1024/sangean_ats_909x.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="766" data-original-width="1024" height="299" src="https://1.bp.blogspot.com/-4eAUjcYX6tY/YVA-B81-SXI/AAAAAAAADLY/n5rYR2Q_OhACwe7JO4VsFXl4-Ish_E7aQCLcBGAsYHQ/w400-h299/sangean_ats_909x.jpg" width="400" /></a></div><br /><p>I also have a Sangean ATS-909X, a newer model to the old '909. There is also an even newer model just out, the ATS-909X2, available on Amazon. All the 909's are beautiful looking radios. I love mine and actually prefer it to the PL-880, though it performs about equally. I find that radios you buy have a certain "feel" about them, independent of their performance. I call it "fun factor". The 909X has greater fun factor for me for some reason.</p><p><a href="https://www.amazon.com/SANGEAN-Ultimate-Multi-Band-Radio-ATS-909X2/dp/B08MSXX6LH">https://www.amazon.com/SANGEAN-Ultimate-Multi-Band-Radio-ATS-909X2/dp/B08MSXX6LH</a></p><p>On the PL-660 and PL-880 comparison. I don't have a '660 but always wished I'd tried one. I do have an older Tecsun PL-600, sort of the predecessor to the '660. They are analog radios, superhetrodyne design. They are good radios, and the '660 is probably equally able as the '880. However, the '880 will have better bandwidth options since it uses the DSP chip, which is very nice to have. I suspect the speaker sound is better in the '880 too. Sensitivity may be about equal. Tuning may be preferable on the '880 as well, especially for SSB.</p><p>On shortwave, all of these radios will improve with a little wire clipped to their telescoping whip antennas. Just a word of advice - be careful when connecting outside long wires to them. Static discharge can destroy them in a hurry. I have ruined two - an old Sony ICF-2010 years ago, and the Sangean '909 I have. I was able to send the '909 in for repairs under warranty and it came back in perfect shape, luckily.</p><p>In these modern times we are plagued with RFI - radio frequency noise from all kinds of devices. Try listening outside away from your house if you have problems. Or even go to a park.</p><p>Three different web entities produce up-to-date shortwave schedules. They are:</p><p>EIBI <a href="http://www.eibispace.de/">http://www.eibispace.de/</a></p><p>NDXC (AOKI) <a href="http://www1.s2.starcat.ne.jp/ndxc/">http://www1.s2.starcat.ne.jp/ndxc/</a></p><p>HFCC <a href="http://www.hfcc.org/data/">http://www.hfcc.org/data/</a></p><p>I find EIBI and NDXC rather good. You can download them for free. Once unzipped you will find text files that you can look at.</p><p>China has a huge presence on shortwave, and I find listening to them rather fun, especially their music. Radio Romania has a nice signal into the US. Also Turkey and Greece, and I love their music as well. I often listen to Radio New Zealand at night. Sadly, Australia is not on any more. BBC still has a presence, mainly out of their Ascension Island relay, Asia and the Middle East. Also Voice of America. Lots of signals coming out of Africa. There are many others.</p><p>For best results, learn to listen at the right times. After dark and at sunrise/sunset times, check the 4-10 MHz bands. During the daytime and at sunrise/sunset times, check the 10-21 MHz bands, particularly 11500-12100 KHz, 13500-14000 KHz, and 15000-15800 KHz. Best times are actually the hours right around sunrise and sunset. Where you are on the west coast, check for Europe late in the afternoon through the evening. Asia will be dominant during sunrise hours. Listen for long path propagation, a weak, warbly signal with an echo, indicating reception from both directions. It is indeed possible and happens all the time, but you need a good antenna usually. Consult those shortwave schedules frequently. Find yourself a nice world map clock off the web, showing a world map with the light and dark areas of the world for the current time. "Simon's World Map" is a great little clock-map that is free and you can install it on Windows. It's by the guy behind the HF+Discovery SDR radio I think.</p><p><a href="https://www.dit-dit-dit.com/world-map">https://www.dit-dit-dit.com/world-map</a></p><p>The last five years or so I've gotten into SDR radios, software defined radios. I have an SDRPlay RSP1A (Ham Radio Outlet has them) and an HF+Discovery. Either is about $120. They would have been the equivalent of a $3000 military grade radio back in 1970. They are cigarette pack sized and plug into your USB slot. You tune and use them through software on your computer. They have spectrum displays and lots of bells and whistles that you'd never find on a portable. If you get deep enough into the hobby you might want to try one of these as the entry price is certainly very reasonable. They require an outside antenna for shortwave, or a loop can be used very effectively for the medium wave band.</p><p>Hope this has been helpful and has given you some ideas. Let me know how it goes. Have fun.</p><p>Bill</p>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com0tag:blogger.com,1999:blog-4260200412608523752.post-49576353431063099982020-12-08T14:39:00.025-05:002022-05-27T17:24:56.796-04:00The RFI Menace And Reduced Noise Antennas<p><b>THE RFI MENACE</b></p><p>Having been in this game for 60 years, I can say that RFI and line noise has grown out of control, and especially since the advent of the cheap controller chip + home computers + digital communication + smart TVs + micro-electronics, et-al. And by "out of control", I mean that the crescendo of noise on the bands is becoming virtually impossible to identify and corral. Back in the 1980s when it started getting worse, it was still possible to identify sources and eliminate them using time-worn choke-suppression methods. Now, not so much. The genie is out of the bottle and it ain't going back in.</p><p>One of the best tools I have found to identify RFI is a spectrum analyzer. No, a $2000 unit isn't necessary. You already have one if you own an SDR receiver. I have an SDRPlay RSP1a, purchased at $119 U.S. and it's quite easy to take a look at any frequency from 10 KHz on up to see where the problem areas are. Spread a short wire across the floor in the house, connect it up, and you will see all kinds of mysterious RF. A pocket or portable sniffer receiver can work for this too but it's much easier to see the RFI's extent on an SDR receiver's spectrum display. The sniffer receiver is better used to locate the RFI.</p><p>I currently use my <a href="https://www.amazon.com/RADIWOW-Portable-Receiver-Activities-Parents/dp/B07WPSY4DG">RadiWow R-108</a> as a sniffer receiver when walking around the house or property. This is used once the RFI "problem" frequencies are identified on the analyzer. Your Tecsun PL-380, PL-310, or other portable receiver can do the same.</p><div><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-smEgd_c2QM8/X8_PI2GOEtI/AAAAAAAAC_I/MoYgGlFiQ6s_Zx0fr1Q1h-9QKthdDhR3gCLcBGAsYHQ/s726/rfi_hash.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="726" data-original-width="709" height="400" src="https://1.bp.blogspot.com/-smEgd_c2QM8/X8_PI2GOEtI/AAAAAAAAC_I/MoYgGlFiQ6s_Zx0fr1Q1h-9QKthdDhR3gCLcBGAsYHQ/w391-h400/rfi_hash.jpg" width="391" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">RFI hash @ 500 KHz - the elevated noise floor is -85 dBm! NOT signals!</td></tr></tbody></table><p><b>THE BIG OFFENDERS</b></p><p>Let's go over the big RFI offenders to our DXing. The big offenders at my DXing home are:</p><p>My Hewlett-Packard 24 inch computer monitor. Huge, wideband, low frequency buzzing in a range across the VLF, longwave and lower mediumwave bands, particularly in the 300-900 KHz segment. The switching power supply creates some of this but the majority comes right off the screen's surface when the display is lit. Efforts to reduce this RFI have only been mildly successful, but luckily its range is only about 15 feet. The downside is the radios need to be within 15 feet of the monitor, particularly the SDR.</p><p>My laptop's switching power supply. I have a recent (2020) Acer Nitro 5, 15.6 inch, with AMD Ryzen 5 4600H mobile CPU. Huge, wideband, low frequency hash between 0 and 600 KHz. Virtually all of this disappears when running on battery only. You can't run on battery forever, however.</p><p>Old style fluorescent lighting, particularly the old 4 ft. shop lights. Best is to just keep them turned off.</p><p>Light dimmers. Don't use them. Keep them off or remove them.</p><p>LED light bulbs for house lighting. The bad ones create a high frequency hiss. Luckily the range is only a few feet, but the house is full of them now due to power saving measures. Use good quality LED bulbs. Philips has been highly recommended.</p><p>Low voltage lighting used in the kitchen. Lots of wiring through the walls go to a transformer box in the cellar. When the lights are on they inject an additional huge buzz at the lower end of the mediumwave band, peaking at about 550 KHz. The emissions from these range throughout the house. The condition is virtually eliminated by keeping the lights off.</p><p>A myriad of switching "chopper" style wall transformers. Some are much worse than others. Try to identify the worst offenders. I try to put all of these on power strips so I can switch them off when not in use.</p><p>Unknown sources of frequency spikes. Strong 10 KHz spaced spikes from 9 MHz to 16 MHz, peaking in the 9.5-9.9 MHz and 10.7-12.5 MHz area. This one is intermittent. It can last ten minutes or an hour or more, then disappears. <strike>I have not ruled out that this signal may be coming from the mains feed to the house.</strike></p><p>**Note: this RFI source just above has been identified. It comes from a $2000 Fisher & Paykel kitchen refrigerator. Fisher & Paykel is a major appliance manufacturer which is a subsidiary of Chinese home appliance manufacturer Haier. It is a multinational corporation based in East Tamaki, New Zealand. In 2012, Haier, a major Chinese appliance manufacturer, purchased over 90% of Fisher & Paykel Appliance shares. Partial solution: wrapping the power line cord through two Workman RFC-1 snap ferrite cores has reduced the problem 50%. More cores have been ordered.</p><p>A new 43 inch Toshiba smart TV and DISH satellite box combo. Tremendously strong RFI, a high-pitched squeal in the LW and MW bands coming out of these boxes out to a 6-8 ft. radius, which then couples to lines. It might be possible to put these on a switchable power strip, but then you have the device reboot problem every time you want to use them. Satellite box boot time is often 5 minutes. That's a no-go.</p><p>Those are just the biggest offenders. Not mentioned is the RFI coming off the computerized de-humidifier in the cellar, the computerized water conditioning system, and the two computerized heat pumps hanging off the back of the garage.</p><p>So you can see the frustration. It's not practical to try to eliminate all of this RFI unless you'd like a lifetime career in RFI removal. I suspect this is the case almost everywhere.</p><p><b>ANTENNA SOLUTIONS FOR NOISY ENVIRONMENTS</b><span style="white-space: pre;"> </span></p><p>Being a ham as well, I've experimented with just about every wire antenna you can imagine over the last 60 years. My days of winding power line chokes are over. Common-mode chokes, current isolators, et al, are the rage these days - these to reduce RF pickup on the feedline and to lessen the possibility of the feedline from becoming part of the antenna system. They can help, but they are a Band-Aid to the real problem. Why not lessen the noise in a different way? My solution is to build inherently quiet antennas which are resistant to noise, and feed them correctly. </p><p>Three things are important.</p><p>1. Get the antenna well away and out of your house.</p><p>An end-fed longwire attached to your shack window fed with 15 ft. of coax across the floor isn't going to do it. If possible, on your lot, put the feed point as far away as you can. This, for starters, is one of the most important things you can do. Don't worry about cable feed length. Coax feed at mediumwave or even shortwave frequencies has minimal loss. 100 feet of the old 50 ohm RG-58 on mediumwave presents only about 0.37 dB signal loss, virtually unnoticeable. RG-6A TV coax, 75 ohm, is even less at about 0.28 dB per 100 ft. I use RG-6A here almost exclusively, as it is cheap and readily available through many suppliers.</p><p>So, get that feed point as far away from your house as possible.</p><p>2. If you can, choose an antenna that is basically a short circuit. What did you just say?</p><p>Loop antennas are essentially short circuits to high frequency impulse noise. Long wires, verticals, and dipoles are not. They are RFI magnets, and particularly so if they are not balanced antennas (the dipole is at least balanced). Much of the high frequency noise component of RFI is short circuited in the loop. Small loops are even better for noise suppression, but their drawback is they often need active amplification due to lower signal delivery. Loops work well when placed close to the ground and you don't need high supports for wires.</p><p>They can also be laid flat on the ground itself which reduces RFI even more. This is where our Loop-on-Ground antenna will come in.</p><p>3. Use an isolating transformer at the antenna feedpoint. Very important. Feed any antenna with a transformer-balun isolating device, even if it is naturally a 1:1 match. There must be no common ground connection between the coax feedline and the antenna, i.e., between the primary and secondary of the transformer-balun. The antenna should remain floating and the coax remain floating. This isolating-matching device does three things which help abate noise:</p><p> 1) Matching the antenna greatly increases received signal strength. Increasing signal strength often will raise the signal above the noise floor. Remember when receivers had preselectors to peak the antenna, which made the difference of hearing a signal or not? This is what a broadband matching transformer is actually doing - matching the antenna to the receiver across a wide range of frequencies.</p><p> 2) The transformer, at least the one we will use, totally isolates the antenna from the receiver, eliminating the direct wire connection and lessening RFI picked up by the antenna from transferring to the coax. Much of the RFI will be consumed in what I call the secondary, or load side (antenna side) of the balun, as it appears as a direct short to the high frequency component of noise.</p><p> 3) The transformer/balun reduces antenna loading because it presents a proper load impedance to the antenna. Loading down the antenna destroys bandwidth and lowers signal strength. Take a longwire for example. A longwire antenna has an inherently high feed impedance, generally 450 ohms, nothing near the usual 50 ohms of a receiver. With no matching device, the input signal delivered to the receiver is a simple resistance ratio. The signal is delivered through a 450 + 50 ohm series divider. The receiver gets 50/500ths of the available signal without the proper transformation. That's 1/10 of the signal being picked up by the antenna! No wonder my receiver can't hear!</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-qRHilgvR4AY/X8_MdovatwI/AAAAAAAAC-8/_j-bYMO4mMY0sqGZgJx2g_6ggmhGs2NgQCLcBGAsYHQ/s420/balun-one-nine.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="281" data-original-width="420" src="https://1.bp.blogspot.com/-qRHilgvR4AY/X8_MdovatwI/AAAAAAAAC-8/_j-bYMO4mMY0sqGZgJx2g_6ggmhGs2NgQCLcBGAsYHQ/s320/balun-one-nine.jpg" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">The Balun One Nine by NooElec, a 9:1 balun</td></tr></tbody></table><br /><a href="https://www.amazon.com/dp/B07XJRTF94/?coliid=IMLEEKSETRJZ3&colid=37NCH9FVV08GV&psc=1&ref_=lv_ov_lig_dp_it">Balun One Nine on Amazon</a>. NooElec makes a cool little 9:1 ratio balun transformer for about $15.<br /><p><b>ANTENNAS WITH GOOD NOISE RESISTANCE</b></p><p><b>The Quarterwave Folded Monopole antenna.</b> Everybody starts out in radio trying a longwire or dipole. These are huge noise magnets in RFI-prone locations. If you are an old timer you remember the folded dipole. It traditionally was a halfwave length antenna, like the dipole. It too is essentially a short-circuited antenna as it loops back on itself at the mirrored low impedance node, opposite the feed point. Another version of the folded dipole is the quarterwave folded monopole, a vertical, though it can be configured in other positions. It is half of a folded dipole. The quarterwave folded monopole is also short-circuited and is easily grounded as well. It's inherent impedance is 150 ohms at resonance (468/f-MHz), half that of the 300 ohm halfwave folded dipole, so if possible use a 3:1 matching balun to get to 50 ohms. If you don't have a balun, don't worry too much about using one on this antenna as the 3:1 matching discrepancy isn't that far off. If the antenna can't be erected as a vertical due to height restrictions it can be run as an elevated end-fed antenna of any length. Possible configurations are an end-fed inverted-V (feed end starts at ground, high in the middle) or an end-fed slanted wire (feed end starts at ground).</p><p>This antenna is essentially a transmission line antenna. Keep the wires parallel and anywhere from a quarter inch to an inch apart. Erected as a vertical, it has great low angle response for that extremely distant DX.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-QnCW8zzh92E/X9y51LDVAjI/AAAAAAAADAo/OdN5ytQeoAAAUskH0rJmjwDQjzl-KrZ8ACLcBGAsYHQ/s746/qw_folded_monopole.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="381" data-original-width="746" height="326" src="https://1.bp.blogspot.com/-QnCW8zzh92E/X9y51LDVAjI/AAAAAAAADAo/OdN5ytQeoAAAUskH0rJmjwDQjzl-KrZ8ACLcBGAsYHQ/w640-h326/qw_folded_monopole.jpg" width="640" /></a></div><p><b>The LOG antenna, or Loop On Ground</b> is another variation of the close-circuited loop only it lays flat on the ground. It is also best fed with a balun. A spool of 100 ft. of 18 gauge wire on Amazon will only cost you about $9. Lay it out in a square, 25 ft. to each side, and feed it at a corner. It is an excellent low noise performer, though with shorter lengths of wire the signal pickup is quite reduced. My 100 ft. length lying on the ground shows close to 15 db less noise than the 6x12 ft. flag antenna in the tropical band (60 meters), with about equal signal strengths. The difference is in the substantially better signal-to-noise ratio. A 15 dB reduction in noise while holding the same signal strength as the flag antenna is a 15 dB SNR improvement!</p><p>I've written an extensive article on the Loop-on-Ground antenna which might be of interest:</p><p><a href="http://radio-timetraveller.blogspot.com/2022/05/the-loop-on-ground-antenna-for-noise.html">The Loop-on-Ground Antenna For The Noise-Challenged</a><br /></p><p>The LOG antenna is somewhat directional, having a fattened hourglass pattern, with slight nulls at the feed corner and the corner opposite the feed. Both high and low angle reception are good, within its range. Best results are when the overall loop length is about 15% of a full wave for the frequency of interest. A 60 ft. total length works well for the 2-8 MHz range.</p><p><a href="http://www.kk5jy.net/LoG/">KK5JY has an excellent article</a> on the Loop On Ground antenna, with illustrations. Be sure to check it out.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-chZWvRnBsy4/X9ETxMv6kRI/AAAAAAAADAI/XU-kbkJght0dM_fl3kVMYM9ZWoX3SKoeACLcBGAsYHQ/s732/flag_antenna.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="288" data-original-width="732" height="253" src="https://1.bp.blogspot.com/-chZWvRnBsy4/X9ETxMv6kRI/AAAAAAAADAI/XU-kbkJght0dM_fl3kVMYM9ZWoX3SKoeACLcBGAsYHQ/w640-h253/flag_antenna.jpg" width="640" /></a></div><p><b>The Flag Antenna</b> is a smallish but very efficient antenna especially for mediumwave work. It is usually configured in the shape of a rectangle and is easily ground-mounted if outside. I have a 6 ft. tall by 12 ft. long flag antenna erected indoors on the second floor, running east-west. The lower wire runs along the floor. Two 6 ft. fiberglass rods form the uprights for the ends. Although my house is very noisy with RFI, the noise pickup on this antenna is very low. The rectangle is broken at one corner on the floor nearest the radio, a vintage tabletop Allied A-2515. A 9:1 balun is used to match the antenna to a short 9 ft. length of coax feeding the receiver. Even un-amplified, this broadband flag has wonderful sensitivity from the AM broadcast band through about 6 MHz. On the mediumwave band, it is about the equivalent of a 4 ft. passive loop which is usually tuned.</p><p><b>The BOG antenna, or Beverage On Ground</b> is a good choice if you have the room on your property. It is basically a very long wire laid on the ground (100 ft. or more) and may be terminated through a resistor to ground at the far end. Termination to ground gives it directional characteristics off the end. It is a variation of the classic Beverage antenna, which is usually a few feet off the ground.</p><p><b>FEEDING A POCKET OR PORTABLE RADIO HAVING NO EXTERNAL ANTENNA</b></p><p>For the AM broadcast band, feeding any of these low noise antennas to a pocket or portable radio is easy. I find inductive coupling best. Salvage a short ferrite rod or bar from an old pocket radio. Three inches in length is about right. Remove all the magnet wire from it. Using some solid, insulated telephone wire of about 24-26 gauge, wind about 15-20 turns close-wound around the ferrite rod. Solder or clip the two ends of wire from this coil to the coax feeder coming from the antenna, one to the center and one to the shield. Hold the ferrite close to the radio's internal ferrite which will inductively-couple the signal to the radio. The advantage over a passive loop here is you have a broadband antenna which does not have to be tuned.</p><p><br /></p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-WCRTdOg1k7E/X8_Ss-K6JHI/AAAAAAAAC_U/kh5eooVAqUsv6eI7QEzeT-KLyie-siPugCLcBGAsYHQ/s450/loop_teaser.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="349" data-original-width="450" src="https://1.bp.blogspot.com/-WCRTdOg1k7E/X8_Ss-K6JHI/AAAAAAAAC_U/kh5eooVAqUsv6eI7QEzeT-KLyie-siPugCLcBGAsYHQ/s16000/loop_teaser.jpg" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Inductive pickup loop</td></tr></tbody></table><p>Shortwave antenna coupling to the pocket or portable is more difficult. A simple clipped wire to the telescoping antenna can greatly increase the noise pickup. If your radio does not have an external antenna jack to safely connect the coax feeder with adaptors then you might have to perform surgery on the radio. Be sure to ground the coax shield to the radio's ground. In any event, be extremely careful if directly connecting outside wire or coax to these modern DSP radios. I cannot stress this enough. You can easily fry the inputs to them. I destroyed a $200 Sangean ATS-909X this way two years ago. Luckily it was still in warranty and I was able to get it repaired and reprogrammed.</p><p><b>NON SHORT-CIRCUITED ANTENNAS</b></p><p>Antennas that are not essentially short-circuited can work but be aware they will capture more noisy RFI. Above ground dipoles or end-fed longwires are two such types. Be sure to use a matching device in any case, which will help.</p><p>I hope this has been helpful to you. Please experiment!</p>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com0tag:blogger.com,1999:blog-4260200412608523752.post-63035925848267729842020-10-12T06:20:00.018-04:002023-06-18T04:56:24.806-04:00Notes On Soft Mute And Analog Tuning In DSP Radios<p>On the surface, soft mute in the modern DSP-chipped receiver seems a bit mysterious. What is it? How does it work? Why do we have it? In this article we'll explore how soft mute works and explain its technical details.</p><p>As a side topic, but somewhat related to soft mute, we'll also tackle the pseudo-analog tuning of the Silabs 483x DSP chip and see what's up there. This is the chip used in many of the cheap portable and pocket radios found today. They are mechanically tuned with a dial knob and have a traditional AM band scale with dial indicator. But they aren't the pocket radio you remember from the old days.</p><p>So let's get right to it.</p><p><b>SOFT MUTE</b></p><p>What is soft mute?</p><p>Soft-mute is a further lowering of the audio level of the received signal when it drops below a prescribed signal-to-noise ratio. It was implemented in consumer grade DSP radios 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: "....to attenuate the audio outputs and minimize audible noise in compromised signal conditions."</p><p>Soft mute attenuation is available in the Si473x digitally-tuned series of chips as well as the Si483x analog-tuned series of chips. The soft mute feature is triggered by the SNR (signal-to-noise) metric. The SNR value is directly readable by the chip's software when you tune to a station. The software reads the quality of the signal through its SNR value and makes soft mute changes accordingly. The SNR threshold for activating soft mute is programmable, as are soft mute attenuation levels, attack/release rates and attenuation slope.</p><p>The Tecsun PL-380, PL-310, PL-330, and other radios all may set different soft mute values than the chip's default values shown below. Settings for soft mute are initialized during the power up sequence.</p><p>The 4 soft mute parameters: Rate, Slope, Max Attenuation, Threshold.</p><p><b><u>Rate (default)</u></b>: 278 dB/second (range 1-255, actual figure 278 = setting * 4.35)</p><p>Determines how quickly the soft mute is applied/released when soft mute is allowed (enabled). </p><p><b><u>Slope (default)</u></b>: 2 dB (range 1-5 dB per dB below SNR threshold)</p><p>The attenuation slope for soft mute application - in dB of attenuation per dB SNR below the soft mute SNR threshold. Translated: how much audio attenuation is applied as the SNR and signal quality decreases. A setting of 2 will lower the audio by 2 dB for each 1 dB reduction of SNR below the starting threshold at which soft mute kicks in. An example: soft mute starts to kick in when the SNR decreases to 10 dB. At 10 dB, there is 0 dB of soft mute. When the SNR decreases to 9 dB, soft mute reduces the audio level by 2 dB. When the SNR decreases to 8 dB, soft mute reduces the audio level by another 2 dB (4 dB total). By the time the SNR hits 2 dB, the soft mute has reduced the audio level to a max of 16 dB. It will go no lower as the max soft mute has been applied. Note that every 6 dB of audio reduction is a halving of the audio voltage level. 12 dB of reduction is then 1/4 of the original audio voltage level. 16 dB (max soft mute) is a reduction of 84.2% (0.158).</p><p><b><u>Max Attenuation (default)</u></b>: 16 dB (range 0-63 dB, max attenuation of soft mute)</p><p>If set to 0, soft mute is disabled entirely.</p><p><b><u>Threshold (default)</u></b>: 10 dB (range 0-63 dB, SNR at which soft mute starts to engage). Silabs states, "for a tuned frequency".</p><p>Note that the Threshold setting is applicable only "for a tuned frequency". I take this to mean that soft mute is dis-engaged totally when not tuned to an exact 9 or 10 KHz channel, which is apparently why the 1 KHz off-tuning hack works.</p><p style="text-align: left;">What you're hearing when a signal's SNR lowers below the threshold and the soft mute kicks in is the Slope factor in action. The Slope factor is lowering the audio volume accordingly.</p><p style="text-align: left;"><b>.....</b></p><div style="text-align: left;">How to defeat soft mute?</div><div style="text-align: left;"><br /></div><div style="text-align: left;">Soft mute can be somewhat minimized by increasing signal strengths to the radio by using a directly-coupled loop, passive loop or other inductively coupled antenna. What happens is you are increasing signal levels, thus improving the SNR, making the signal exceed the threshold where soft mute is engaged.</div><div style="text-align: left;"><br /></div><div style="text-align: left;">The other (original) hack is to tune off the channel by 1 KHz and raise the volume on the radio. Being off-channel disables soft mute.</div><p><b>.....</b></p><p>Two other interesting parameters effecting tuning and seeking, not related to soft mute.</p><p><b><u>AM Seek/Tune SNR Threshold.</u></b></p><p>SNR Threshold which determines if a valid channel has been found during Seek/Tune.</p><p>Specified in units of dB in 1 dB steps (0–63). Default threshold is 5 dB.</p><p>This tells us that when you do a scan, only stations with >5 dB SNR are eligible to be stored.</p><p><b><u>AM Seek/Tune Received Signal Strength Threshold (RSSI).</u></b></p><p>RSSI Threshold which determines if a valid channel has been found during Seek/Tune.</p><p>Specified in units of dBµV in 1 dBµV steps (0–63). Default threshold is 25 dBµV.</p><p>This tells us that when you do a scan, only stations with >25 dBµV RSSI are eligible to be stored.</p><p><b>.....</b></p><p><b>THE ANALOG TUNING ALGORITHM</b></p><p>The Silabs 483x series of chips are analog tuned and they have no digital LCD display. Tuning is accomplished through a tuning knob connected to a 100K ohm potentiometer. They attempt to mimic the analog tuning of the old traditional analog superhet radios when you "sweep" through a station's carrier. Silabs has developed a special tuning formula in software to simulate this. From the DXer's point of view it doesn't work. I've given a lot of thought to how their algorithm works in software.</p><p>Over the summer here in North America I have bought quite a few of the cheap Chinese analog-tuned DSP Ultralights. Though I have found some can be quite sensitive (like the Sangean SR-35 and the ultra cheap Dreamsky Pocket Radio), the SiLabs tuning algorithm is still wonky and masks a lot of weaker adjacent channel signals. It becomes tedious for serious DXing. Poor selectivity and overload problems can also be evident on these units, depending on the unit.</p><p>As stated, the problem with the current analog-tuned theory is that a weaker adjacent channel signal is masked deliberately if next to a more overwhelming signal.</p><p>A typical tuning scenario goes like this. Find a strong station where you know a weaker station sits right next to it on the adjacent channel. The weaker station would be strong enough to be received on a normal superhet radio. With the Silabs 483x radio, tune to the strong station's channel. Now tune to the adjacent channel (the weaker station). The strong station is still there, only at a slightly reduced volume. The radio is attempting to mimic tuning "through" a station like in the old days, increasing the strength of the station as you approach its channel center, then decreasing the strength as you depart. But where is the weaker station?</p><p>Here is what is happening in software (I think), preventing you from receiving the weaker adjacent channel.</p><p>Let's say the following numbers below, 0 | 5 | 20, represent frequencies 1020, 1030, and 1040 KHz. 1020 KHz has no signal on channel. 1030 KHz has a weak signal of SNR 5 dB. 1040 KHz has a strong signal of SNR 20 dB.</p><div style="text-align: left;"><span style="font-family: courier;"> FREQ 1020 1030 1040</span></div><div style="text-align: left;"><span style="font-family: courier;"> SNR = 0 | 5 | 20</span></div><p>In these DSP radios, hardware generates a tuning interrupt in software when changing the tuning knob. It causes the software to take over and analyze what just happened. </p><p>Initially, tune to 1040 KHz from somewhere above in frequency and begin receiving the strong station.</p><p>Now tune to 1030 KHz. Software then does this:</p><p>1. The tuning interrupt is generated.</p><p>2. Hard mute the audio.</p><p>3. With audio off, electronically retune to the new channel (1030) and test the new channel's SNR. If valid (SNR >= 5 dB), remain on this new channel and unmute the audio. If not valid (SNR < 5 dB), electronically retune back to the original channel (1040) and reduce the audio 6 dB and unmute. The dial will point to 1030 even though we're hearing 1040.</p><p>Now tune to 1020 KHz. Software then does this:</p><p>1. The tuning interrupt is generated. Remember, though the radio dial shows 1030 KHz, the radio is still electronically tuned to 1040 KHz.</p><p>2. Hard mute the audio.</p><p>3. With audio off, electronically retune to the new channel (1020 this time) and test the new channel's SNR. If valid (SNR >= 5 dB), remain on this new channel and unmute the audio. If not valid (SNR < 5 dB), electronically retune back to the original channel (1040) and reduce the audio an additional 6 dB and unmute. The dial will point to 1020 even though we're hearing 1040.</p><p>Additionally, for each of the two scenarios above, we must also be sure in step 3 that the original 1040 channel maintains a SNR above the SNR of the newly tuned channel or we force-tune to the new channel.</p><p>Electronically retuning the DSP chip is simply a matter of electronically setting the proper internal capacitance to resonate with the ferrite coil at the desired frequency. It's done with a single software command.</p><p>It's complicated.</p><p>If you start at 1020 KHz then approach 1030 from below the situation changes, as we are comparing 1030 to 1020 now, 1020 having no signal at all. If 1030 is a valid channel (SNR >= 5 dB) then the DSP chip tuning remains at 1030, the hard audio mute is unmuted, and the station is received. Drawing from this scenario, we can conclude that if we approach a weak signal from the right tuning direction that we might be able to hear it.</p><p>Compounding the problem, these 483x chips also generally have soft mute enabled, which may mask very weak stations. The weak station will still need to overcome the soft mute threshold to some degree.</p><p>According to Silabs, this new tuning algorithm has been "audience tested" to a positive level of acceptance. The best approach for the DXer would be to have a radio where soft mute is disabled altogether and no tuning algorithm so that when you move the tuning dial it always changes the frequency.</p><p>Surprisingly, this wonky tuning algorithm can be somewhat minimized by increasing signal strengths to the radio by using a directly-coupled loop, passive loop or other inductively coupled antenna. What happens is you are increasing signal levels, thus improving the SNR, so the signal meets the threshold requirements for a valid signal. The radio then tunes to the proper signal and frequency.</p><p>A description of even weirder analog tuning anomalies can be read here:</p><p><a href="https://radio-timetraveller.blogspot.com/2023/05/notes-on-xhdata-d-219-analog-dsp-radio.html">Notes On The XHData D-219 Analog DSP Radio</a></p><div style="text-align: left;">I hope this analysis of soft mute and the DSP analog tuning mechanic has proven useful and interesting. All technical data has been gleaned directly from Silabs data sheets for the respective 473x and 483x DSP chips. The programming guide for these chips was particularly helpful in understanding the operation of soft mute.</div><div style="text-align: left;"><br /></div>RADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.com2