Many thanks to SWLing Post contributor, Nick Hall-Patch, who shares the following article originally published in the IRCA’s DX Monitor:
2024 Solar Eclipse DXing
by William Scott, WE7W
DXing the mediumwaves promises to be an exciting event on April 8 during the 2024 total solar eclipse. 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:
- Scenario 1. For those who live within or very near the path of totality (see Figure 1), 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.
- 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.
- 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.
I think that scenarios #1 and #2 have the best possibility for DX.
Figure 1 (Click to enlarge)
Across the U.S. and Canada, from its entry at Texas to its exit through NE Canada and into the Atlantic Ocean, the totality path width varies from a maximum of 199 km at U.S. entry to about 160 km at Atlantic exit, or 123 to 99 miles.
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. 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.
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. 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 Cincinnati, OH, WHAS-840 in Lexington, KY, and others along or near that path.
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.
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. 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% at maximum.
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.
A presumed Scenario #4.
Another scenario was suggested by Nick Hall-Patch, that of reception parallel to the path of totality and outside the 100% totality band. The 2017 solar eclipse across the northern part of the U.S. was DXed extensively and produced some interesting results, which are well documented in IRCA Reprints. Check their document repository here:
http://dxer.ca/images/stories/2019/irca-reprint-index.pdf
Nick reports: “The receptions of KSL-1160 described in IRCA Reprint # G-096 showed the results of 3 DXers listening across the path of the eclipse (Scenario #2), but the fourth, Dave Aichelman, was monitoring KSL from a location parallel to the eclipse path ( sort of Scenario #1?) and got very good enhancement as well.” We might name this “Scenario #4”.
I checked out # G-096, that documents the KSL reception from the solar eclipse of 2017. It looks like the Dave Aichelman (at Grants Pass, OR) reception of KSL had a mid-path reflection point of about 95% solar obscurity. The distance was 971 km (602 miles). Graphing KSL, I see it has a nice fat low angle takeoff and impressive skywave strength at 900 km, some 1.3 mV/m for that distance. (ed. note: A map of fractional solar obscuration is in Figure 2, easily converted to the percentage figures quoted in this article. )
Better yet, the article indicated Aichelman also received XEPE-1700 across the Mexican border from San Diego too. That was a mid-point reflection obscurity of only about 83% as far as I can deduct from the maps. The distance was 1238 km (769 miles). The mid-path reflection point there was in the neighborhood of 700 km from the central path of totality.
So, DX is indeed possible where both the station and the receiver are off center from the totality path. It’s looking like anything from at least 80% obscurity at mid-path reflection may have some real possibilities, particularly if you are at the end nearest the path of totality. Lower obscurities, perhaps down to 50% or so may even produce results.
Check out these links.
https://nationaleclipse.com/cities_partial.html
https://eclipse.gsfc.nasa.gov/SEpath/SEpath2001/SE2024Apr08Tpath.html
https://eclipse2024.org/eclipse_cities/statemap.html
Using my pattern mapping program which has extensive area search capability, I’ve compiled a list of all US and Canadian stations that fall within the 2024 Solar Eclipse path of ~100% totality. There are 456 stations. Results are drawn from the March 20 FCC LMS database and Industry Canada database. Sorry I don’t have Mexico available.
If you would like this list, download from this link. https://www.mediafire.com/file/125ih5yrmw4puib/2024-eclipse-stations-by-longitude.zip/file
Across the US and Canada, from its entry at Texas to its exit through NE Canada and into the Atlantic Ocean, the totality path width varies from a maximum of 199 km at US entry to about 160 km at the Atlantic exit off Newfoundland, or 123 to 99 miles. 456 stations are found in this eclipse path. I purposely set the path width to 210 km from start to finish. This gives a few km slop on both sides of the 100% totality path for good measure.
Unzip the downloaded .ZIP file, where you will find 3 files. The stations in each file are sorted by longitude, from west to east. This gives us the progression of the eclipse path, with the eclipse starting at the first station in the list and ending with the last station.
File #1 is a simple text file.
File #2 is in .CSV format. You can easily input it to an Excel file.
File #3 is in .HTML format. It includes links to each station’s Google Map latitude-longitude coordinates for the satellite view of the transmitter tower array.
Another link takes you to the FCC AM Query link for that station. I hope these files are beneficial. There should be many propagation path possibilities outside of this list as well.
(reprinted from the author’s blog at https://radio-timetraveller.blogspot.com/ )
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Further sources of information concerning the eclipse include the following websites:
(Clicking anywhere on this map page will give all the information you need about obscuration, length of eclipse etc.at a given location). Also:
https://www.greatamericaneclipse.com/april-8-2024
https://eclipsewise.com/2024/2024.html
Animations of the path of the eclipse versus time can be seen at:
https://eclipsewise.com/solar/SEanim400/2024_04_08_TSE_400px.gif
http://7dxr.com/4all/100km8Apr-movie–Frissell-HamSCI.mp4
The latter is particularly interesting, as it shows the moon’s shadow at 100km height above the earth, an area of special interest to DXers, as it is the lower edge of the E-region of the ionosphere. Note especially that as the eclipse ends over the North Atlantic Ocean, that there is a temporary darkness path between Europe and North America, because night will already have fallen in Europe. So will there be blips of TA DX in eastern North America as the eclipse passes by? Listen, and find out!
Finally, our DX could be of interest to ionospheric physicists also. The rapidly changing listening conditions will be indicating a similarly turbulent ionosphere, and DXers’ documenting those listening conditions through SDR recordings could provide information that will be useful to scientists who want to gain a better understanding of the Earth’s ionospheric dynamics.
HamSCI is an organization of volunteer citizen-scientists and professional researchers who study upper atmospheric and space physics, and will be interested in examining MW DXers’ wideband SDR recordings made during the eclipse period, and indeed, in having DXers assist with HamSCI’s research. (see https://hamsci.org/eclipse. Especially if you are an amateur radio operator, there are several other ways that you might also contribute to the project.)
(This first appeared in IRCA’s DX Monitor and is used with permission. See https://www.ircaonline.org/default.php for club details)
I carried out a low-tech version of Bill’s Scenario 1 on Monday April 8th from Arkansas. Rather than scanning for everything I could hear from my location, I was particularly interested in whether DX signals peak when totality is centered over a transmitter location, a receiving location, or somewhere in between. Previous accounts on this issue differ. See for example, Ruth Bamford’s nice write-up from a large UK radio observing campaign of the 1999 total eclipse in Europe, which reported that the best reception may usually occur when totality was located over a distant transmitter, rather than over an observer or somewhere in between (see Table 2 and discussion in RADIO AND THE 1999 UK TOTAL SOLAR ECLIPSE, https://arxiv.org/pdf/1703.01491.pdf).
For my experiment, I traveled to Morrilton, Arkansas (35.1769499,-92.7433297), which would provide over 4 minutes of totality and a chance to listen in both directions as the eclipse swept across the USA . I brought a simple Grundig Eton Executive Traveler III portable radio (no external antenna), and used both my ear and the radio’s digital dBu readouts for signal detection. When we arrived in Morrilton on Sunday April 7th, I oriented the small portable radio to face the direction of the eclipse path, and compared reception scans across the AM band in the late afternoon Sunday, Sunday night, and again Monday morning. Because of the relatively low radio clutter in central Arkansas, I was pleased to find many distant stations that were clearly detectable from Morrilton only after dark, and had no competing signals during the day. I then chose five 50kW stations strategically located along the path of totality that I could monitor as the eclipse approached and receded. Two stations would experience totality before my own location (in the southwest direction in Texas), and three that would experience totality after my location (in the northeast direction in Missouri, Kentucky, and Ohio).
In geographic order along the line of totality, my five strategic stations were:
WOAI 1200 San Antonio, TX (located 518 miles from Morrilton to the SW, with a mid-eclipse time 17 minutes earlier than me at 18:35 UT)
WBAP 820 Dallas, TX (363 miles to SW, mid-eclipse time 11 minutes earlier at 18:41 UTC)
KMOX 1120 St. Louis, MO (278 miles from Morrilton to the NE, mid-eclipse eight minutes later than me at 19:00 UTC)
WHAS 840 Louisville, KY (442 miles to NE, mid-eclipse time 15 minutes later at 19:07 UTC)
WCKY 1530 Cincinnati, OH (528 miles to NE, mid-eclipse time 17 minutes later at 19:09 UTC).
I stored each of these 5 channels in Eton memory registers, and I could then quickly toggle between the preset channels every two to five minutes before and after my local eclipse in Arkansas (mid-totality at 18:52:39). None of the five stations were detectable initially on eclipse day, including during a full hour of partial phase observing in Morrilton (17:33 to 18:40 UTC). However, each of the five channels then came up in the expected geographic sequence, first San Antonio only at 18:42 UTC (10 minutes before Arkansas mid-eclípse), then Dallas, then St Louis, then Louisville, then Cincinnati, before everybody was back to background levels by 19:20 UTC
A few simple observations from this fun radio observing run during the eclipse:
The time of “first audibility” was NOT when totality was located directly over the broadcast site, but somewhere in between the broadcast and receiving site. For example, I couldn’t hear San Antonio or Dallas in Morrilton until about 7 or 8 minutes after totality had passed beyond each of the respective broadcast locations to the SW. Similarly I began to hear Louisville and Cincinnati about 11 minutes before their own respective mid-eclipse times to the NE. Thus in both directions from my location, increased reception was when totality was somewhere between transmitter and receiver, not when totality was centered over one of the other.
The period of increased reception for individual stations lasted about 10 to 20 minutes, with the earlier eclipse stations located to the SW already returning to background when the later eclipse stations to the NE were still being received.
The rise in signal for each station during the eclipse was 20-25 dBu units on the Eton display. Since every 6 dBuV units corresponds to a 2 fold increase in signal strength, this corresponds to an 8 to 16 fold overall increase in signal measured by the internal electronics of my convenient little travel radio. (For comparison, each 6 dBu change corresponds to a one unit change on traditional S-meters of other radios, or a 3 to 4 S-unit boost during the eclipse, see http://radio-timetraveller.blogspot.com/2015/01/the-ultralight-db-mystery-s-meters-and.html?m=)
I feel very fortunate that the bad weather forecasts in TX led us to drive 7 hours into Arkansas for observing. The relocation gave us beautiful clear skies for watching a spectacular total eclipse by naked eye and binoculars (complete with temperature changes, naked eye planets, a wispy corona, multiple gorgeous orange-red prominences that evolved during the 4 minutes of totality, a beautiful diamond ring effect, plus bonus shadow bands visible seen against a white background right after totality). Just as important for my radio DXing project, going to Arkansas put us in a relatively quiet daytime radio reception zone. My original plan had been to observe in Belton TX for the eclipse, a site located within the crowded daytime radio domes of Austin and Dallas. I did some practice radio scans at daytime and nighttime near Belton when I first arrived in Texas on Saturday April 6th. I picked up so many local daytime broadcasts that I think it would have been much harder to pick useful interference-free channels for following fainter DX signals during the eclipse.
Thanks to Joe Rao, whose Sky and Telescope article made me realize that radio observing would provide a good backup project in case I was clouded out visually during the eclipse! Many thanks also to Bill Scott whose radio-timetraveler.blogspot.com site was a great source of additional information. His daytime and nightime North America station broadcast range maps were often invaluable for sorting out what channels I was hearing after AM radio scans, and what might make good DX targets for daytime observing during the eclipse.
David Kingsley,
Stanford CA
I’m in the Chicago area. Somewhat off the totality track. I’m going to be listening for WOAI 1200 am San Antonio as the eclipse starts, and then WHAM 1180 am Rochester NY as the eclipse passes my area. Another one to listen for would be KDKA 1020am Pittsburgh. Good luck to all. Happy Dxing 73s
I have set up my Cheap SDR (RTL-SDR V3) to record at 300 kHz spectrum (1300-1600 kHz) during the eclipse. I live SW of Ft. Worth Texas and will have about 2 and half minutes of totality at 1:40 PM CDT. The recording will occur 45 minutes each side of peak eclipse. I tested what range would be best and the 1300-1600 kHz one had the least interference (close to DFW). The antenna is a 3 Foot Box Loop (Shawn Axelrod design) and will be pointed along the Eclipse path. It currently can hear XERF during this time period. Not bad for a $25 SDR.
I will record Sunday and then again during the Eclipse Monday. I will observe and report on the differences.
In addition, I will do 20 Meters (14 MHz) digital (FT4) recording (decodes) during the event. I will also compare results from Sunday and changes to the MUF figures at the Austin Texas Digisonde.
I did a 15 Meter (21 MHz) test during the October 2023 Annular Eclipse. There were definite changes to signals and the MUF during that one. The current level of Solar activity, plus a few weeks into Spring have determined a move to 20 Meters. I haven’t published my results on my Blog:
https://ka5dwipropagation.blogspot.com/
I will do it after this one for both Eclipses.
73 Art K7DWI
Looking forward to your observations, Art. Good choice on the range for the AM band. I would expect the upper half of the band to have the better propagation.
Surely it is exiting to the Atlantic through South-East (SE) Canada (NL) rather than North-East (NE) Canada (Labrador / Nunavut)?
Sharp eye, BeeTee. It is indeed SE Canada.
Excellent observation, Bob. One might take the weekend to scan the band and list all the very “dead” channels, then look at those frequencies for stations which fit scenarios 1,2,3,or 4 which might make the trip at eclipse time.
Skywave field strength peaks usually at a station-to-receiver distance of 200 – 500 km. I would attach greater priority to stations in that range.
Good luck!
Excellent article; lots of good information.
I have never participated in one of these events; however, it seems to me that some consideration must be given to stations broadcasting in the receiver’s location. Remember, this is not your every-night situation. This will happen during daylight hours and your local stations will be at their normal daylight power and antenna pattern. Therefore, you will have to pick the relatively open frequencies in your local broadcast band and focus on those either not in use or receiving only weak regional stations. I would match these frequencies against more powerful distant stations having some potential to “leak through” during the eclipse.
Good luck to all.
Bob C.
The other handicap I see is that affected stations are unlikely to give over part of their broadcast day to run continuous IDs as the dark spot passes over their tower. That would be most helpful to verify what you are hearing. Sometimes the station can be determined by the content of the advertising or announcements. I have also used streaming services such as TuneIn and iHeart to compare content with over-the-air transmission. Streaming may operate on several seconds delay. You will have to work fast.
Bob