Tag Archives: Bob LaRose (W6ACU)

Guest Post: Eclipse 2017 – Shortwave Propagation Observations

A map of the United States showing the path of totality for the August 21, 2017 total solar eclipse. (Source: NASA)

Many thanks to SWLing Post contributor, Bob LaRose (W6ACU), for the following guest post:

Eclipse 2017 Propagation Observations

by Bob LaRose (W6ACU)

DXers know that the reception of overseas Shortwave Broadcast stations offers one of the best ways to immediately gauge shortwave radio propagation conditions from your location to distant areas of the world. For the eclipse of 2017 I decided to see how reception of SW broadcast stations on lower shortwave  broadcast frequencies (and to a smaller extent medium wave AM) reacted to the short term effects of the eclipse.  

Going into this experiment I suspected that since the eclipse should temporarily reduce ionization to D-layer of the ionosphere, there might be some reduction in corresponding typical D-layer daytime absorption on lower frequencies. The hope was that this would enhance lower frequency propagation, particularly on the path between Asia and Western North America, which is normally totally absorbed at that time of day. I also monitored for propagation on other HF stations such as WWV as well as US-based SW Broadcast Stations in Alaska and Tennessee, and to a lesser extent AM MW broadcast stations. Here are the results of my experiment.  


The Icom -IC-7300

For these tests I was using an ICOM IC-7300 Transceiver as a receiver connected to my standard antenna for lower frequency use – a Carolina Windom with the center about twenty feet off the ground. The antenna works reasonably well over a wide frequency range, including the lower SW and the medium wave AM broadcast bands. Because of my high local electrical noise level and proximity to several local AM broadcast transmitters, I turned off the built-in RF amplifier of the IC-7300 for all the tests. I used the uncalibrated S Meter of the radio to measure relative signal strengths in S units and dB above S-9. 


The day before the eclipse I took baseline measurements at about the time of the eclipse. Because of normal summer daylight absorption, there were no signals present on either the 49 or 41 meter SW broadcast bands. At this time of year signals on those two bands generally fade below the local noise level at my QTH San Diego by about 1500 UTC.  

I also checked the reliable daily beacons on SW at that time are the WWV frequencies of 5 and 10 MHz, The baseline for WWV was a signal strength of S5 on 5 MHz and S7-9 on 10Mhz.  

I also took some baseline measurements of AM broadcast stations in Los Angeles (KFI 640 and KNX 1070). I was not able to receive any of the San Francisco, Sacramento, Las Vegas stations or points further North.  


According the Internet sources the eclipse began in San Diego at 1607 UTC, peaked at 1723 UTC and ended at 1846 UTC. It reached 66% of totality. 

My first observation was at 1550 UTC. The strength of all signals were at the nominal readings from the day before. At 1630 I still did not hear any SW broadcast stations above the local noise level. 

By 1640 the HF broadcast stations had begun to break through the noise. Here is a chart of my reception observations during the observation period:  

Freq KHz  Station and Location  Time in UTC vs. Relative Signal Strength (S Units) 
    1550  1630  1640  1650  1710  1725  1745  1800  1815  1830 
640  KFI Los Angeles  9  9  9  9  9  9  9  9  9  9 
1530  KFBK Sacramento, CA  0  0  0  0  3  6  2  0  0  0 
5000  WWV Ft Collins, CO  5  5  7  9  9  9  6-7  7  5  5 
5845  BBC Singapore (ends at 1700)  0  0  0  9  0  0  0  0  0  0 
5995  Korea – Echo of Hope (presumed)  0  0  0  0  6  0  0  0  0  0 
6015  Korea (presumed)  0  0  0  5  0  0  0  0  0  0 
6045  Korea (presumed)  0  0  0  6  0  0  0  0  0  0 
6125  China National radio  0  0  0  6  0  0  0  0  0  0 
6155  Taiwan (1700-1730)  0  0  0  0  S9+10  5-7  0  0  0  0 
6165  Yamata Japan for Korea (1600-1700)  0  0  6  7-9  0  0  0  0  0  0 
6175  China National Radio  0  0  0  0  5-7  7-9  7-9  0  0  0 
6195  BBC Singapore (open carrier – presumed tune-up for next morning  0  0  0  0  S9+10-20  0  0  0  0  0 
7300  Radio Taiwan  0  0  7  0  0  0  0  0  0  0 
7385  China National Radio  0  0  9  0  0  0  0  0  0  0 
7465  BBC Singapore (ends at 1700)  0  0  S7-8  0  0  0  0  0  0  0 
7485  VOA Thailand (started 1700)  0  0  0  0  7-8  3  0  0  0  0 
7540  VOA Thailand (started at 1700)  0  0  0  0  0  S5-7  0  0  0  0 
9355  Radio Free Asia (Marianas Islds, starts at 1700)  0  0  0  0  5-7  0  0  0  0  0 
9475  WTWW Lebanon, TN  0  0  0  0  0  0  7-9  7  4-6  0 
9655  KLNS Anchor Point, AK  0  0  9  6-7  7-8  0  0  0  0  0 
9965  Radio Free Asia (Marianas Islds, starts at 1700)  0  0  0  0  9  5-7  0  0  0  0 
9980  WWCR Nashville, TN  8  7-9  7-8  7-8  7-8  7-8  7-8  9  7-9  7-8 
10000  WWV Ft Collins, CO  7  S9+10  9  9  9  5-7  9  9  6-8  7-9 
12160  WWCR Nashville, TN  S9+20  S9+10  S9+10  N/R  N/R  N/R  N/R  S9+10  S9+20  N/R 

 N/R = Not recorded 


As the results show, there was a very significant improvement in lower frequency shortwave propagation between San Diego and Asia during the eclipse. The 49 and 41 meter SW broadcast bands in particular went from below the noise level to providing good reception of a number of Asian and Pacific broadcast stations, starting at around 1640 UTC. Stations were received from China, Korea, Mariana islands, Taiwan, and Singapore. All stations fell back below the noise level by 1745UTC. 

Reception of WWV Ft Collins, CO on 5 MHz also greatly improved around 1700 UTC. The 10 MHz signal was not significantly affected. 

As the eclipse moved East, Reception of WTWW on 9475 kHz and WWCR on 9980 kHz from Tennessee peaked at around 1745 UTC. There was no major effect to the WWCR transmission on 12160 kHz. 

On mediumwave AM the only long distance station that I could hear was KFBK Sacramento,1530kHz. The distance is roughly 475 miles. It went from below the noise to an S-6 at peak at 1725 UTC. (Note – I tried the clear channel stations in the Bay Area, Portland, Boise, etc. but none of them were heard. Many of these frequencies have either low power daytime stations or are right next to high power local stations here in Southern California). Reception of KFI 640 kHz Los Angeles (about 90 miles) was unchanged with no sign of typical nighttime selective fading.  

This was an interesting once-in-a-lifetime opportunity for this propagation experiment and the results show that the eclipse conditions can significantly improve certain types of radio propagation over long distances!

Fascinating results! Thank you so much for sharing your report of shortwave radio propagation during the 2017 Solar Eclipse, Bob! 

Bob recalls working at Harris and putting the RF-505A on the air

Fullscreen capture 5102016 114119 AM

In response to our post mentioning the Harris RF-505ASWLing Post contributor, Bob LaRose (W6ACU), writes:

I know the RF-505A very well. It was introduced in about 1969 while I worked at Harris in Rochester. I started working there as a Co-Op student while at RIT and then after I got my BSEE I joined them full time, initially as a Field Engineer but quickly found my way into Marketing and eventually Sales.

Right after the first version came out, the RF-505, I took one home to my parent’s house for a weekend and did some SWLing with it. It was very neat in one respect – it tuned ISB (Independent Side Band) and in those days there were a number of utility stations using ISB (separate traffic on each sideband). To an SWL some of the most interesting of these were the VOA point-to-point links from the East and West Coast, each carrying two simultaneous program feeds for the overseas relay stations!


While overall a good receiver my personal results on the sensitivity of the original RF-505 were not very positive. On the bench with exactly a 50 ohm source it looked good but on a real world antenna it was pretty numb. Eventually, after a lot of internal arguments, they came out with the RF-505A that included a tunable active preselector as shown in the photos. Problem solved.

For a ham or SWL the RF-505 was a real pain in the butt to tune. You could dial in any exact frequency but the decade switches didn’t roll over (either mechanically or electrically) so you had to do a lot of knob twiddling to do any kind of band scanning. The detents on the switches connected to the knobs were pretty stiff so you could easily take some finger skin off tuning around!

If I remember correctly Harris built them for about a five year period and then replaced them with the RF-550, which was a monster of a receiver with all kinds of advanced features. It included a keyboard with electronic display.

Great memories!

Thanks so much for this RF-505A insight, Bob! I had a hunch that band-scanning wasn’t the RF-505A’s strong suit–it would be incredibly cumbersome to scan with so much “knob twiddling.”

It must have been pretty amazing to work for the legendary Harris corporation. Thanks for sharing!

How Bob found his Zenith “Bomber”


After posting a link to Paul Litwinovich’s Zenith Transoceanic article, SWLing Post reader, Bob LaRose (W6ACU) sent me the following message:

“Just a quick story to follow-up on the excellent Zenith Transoceanic article today. It brought back a lot of great memories!

About twenty years ago I decided to collect some of the things that I couldn’t afford when growing up. I acquired quite a number of Hallicrafters receivers and other “heavy metal” including several transmitters (including my Viking I AM Transmitter). In the process of our last move, I got rid of a lot of the collection. One part of the collection that I did keep was my Transoceanics. If I remember correctly I have every major model except the military one mentioned in the article and the very last one.

Here is my story is about obtaining a “Bomber” as described in the article. I was visiting a gun show at the North Carolina Fair grounds in Raleigh (I went there with a friend who is into Civil War collectables). Anyway, we were walking around and I spotted a small dusty suitcase on a table in the back of a booth. It was closed and to anyone else it looked like an old carrying case. However, by the size and the brown leatherette-grained case I thought it just might be a “Bomber”.

I tried not to act too excited and asked the seller what it was. He said it was an old radio and I asked him to bring it out. Sure enough, it was a Bomber! Still trying not to act too excited, I tried to let on that I didn’t know what is was and asked him if it worked. He said he didn’t know. I made a point of saying that it was missing the dial cover (but the pointer was there and unbent and the inside looked pretty clean and even had its “Wave Magnet”).

I asked him how much he wanted and he said $100. We haggled a bit over the condition and I finally got it for $75. I walked away very happy and excited!


I spent some time cleaning it up, de-oxing the contacts and then used a VARIAC to slowly bring up the voltage to reform the electrolytics. But guess what? IT CAME TO LIFE!

I was even able to get the Sam’s manual and do an alignment. I don’t recall that I had to change any electrical parts or tubes and I even found a guy that made a replacement dial cover! It’s not as shiny as the one in the article but it was sure a great find. It proudly sits on the bookshelves in my office along with the Zenith “Sailboat” AM receiver mentioned in the article and my other Transoceanics. I’ve attached a picture of the two side-by-side. [See photos above]”

Many thanks, Bob, for sharing your “barn find”–or should I say “gun show find”(?)– Zenith “Bomber.” What a great story. I’m glad it’s in the hands of someone who has restored it and can appreciate its history. Indeed, your story proves that you never know where you’re going to find a vintage radio deal.

Recording Deutsche Welle Kigali’s final broadcast and remembering its early days

DW's relay station in Kigali (Source: Deutsche Welle)

DW’s relay station in Kigali (Source: Deutsche Welle)

Yesterday, Deutsche Welle transmitted its final broadcast from the Kigali, Rwanda relay station. Since I’ve only had moderate luck hearing the Kigali site the past few days–especially on 31 meters–I fired up the TitanSDR Pro (which is still currently under review) and set it to record all three final afternoon broadcasts from Kigali on 12,005, 15,275 and 17,800 kHz.


As you can see from the screenshot above, Kigali produced a very strong signal on 17,800 kHz. The TitanSDR recorded the full broadcast, starting with one minute of the transmitter tuning, then one hour of DW’s French language service, followed by one hour of DW’s Hausa language service…then the transmitter went silent.

The recording begins around 1659 UTC on March 28, 2015 on 17,800 kHz:

Kigali’s early days

Last week, SWLing Post reader Bob LaRose (W6ACU) sent me the following message and scans:

“Here’s some nostalgia from [when the Kigali relay] opened, 50 years ago!”

Kigali Front

Kigali 2

Bob then followed this with another email:

“I dug into the “vault” and I found [the] 1964 Third Quarter issue of “Hallo, Friends” from Deutsche Welle that talks about the “new” Kigali station as it was being built. The 1965 issues did not cover the actual inauguration.”


Click here to download this page as a PDF.

Many thanks for digging through your archives and sharing this wonderful DW nostalgia, Bob! It’s simply brilliant!

Readers: If you have shortwave nostalgia you would like to share on the SWLing Post, please contact me.