If you are a copyright owner and believe that your copyrighted works have been used in a way that constitutes copyright infringement, here is our DMCA Notice.

« Sensei Rebel's Archive Picks of the Week (3/13/06 - 3/19/06) | Main | What's in the WFMU volunteer's iPod? »

March 20, 2006


TrackBack URL for this entry:

Listed below are links to weblogs that reference Adventures in Amplitude Modulation - Part 12:



I've really enjoyed "Adventures in Amplitude Modulation." You inspired me to pull the old Radio Shack DX 392 (Sangean 818CS) down off the shelf and make some recordings of my own. I look forward to future installments of this series.


Most, if not all, of the stations you were hearing above 49 meters were probably images from strong stations on 41 meters. I wasn't able to find exactly what the intermediate frequency of a BCL-2000 is, but the vast majority of radios have an IF of 455 kHz. A few have IFs of 450 kHz. A single-conversion receiver like the BCL-2000 is susceptible to receiving images of stations at two times the IF above and below the transmitted frequency. 2 x 455 = 910. 6415 + 910 = 7425 kHz; Radio Austria International broadcasts in German on that frequency at that hour. 6555 + 910 = 7465; Brother Stair broadcasts on that frequency at that hour via WWCR Nashville. 6375 + 910 = 7285; Voice of Croatia broadcasts via Juelich, Germany, on that frequency at that hour. 6250 + 910 = 7160; China Radio International broadcasts in Spanish at that hour on that frequency.

I couldn't find a listing for 6295 + 910 = 7205. Probably someone has moved on to that frequency since my references were published. 6295 - 910 is 5385, an unlikely source for a broadcast image.

Dale Hazelton

Hey, Professor.According to the latest issue of Passport to World Band Radio, the only Spanish language station around 00:00 GMT at 6249 is "Radio La Voz" from Peru. Nothing being broadcast to the Eastern US should be in the 6375 area, although there is a AFRTS (Armed Forces Radio) station broadcasting from Pearl Harbor at that time, however their site shows them broadcasting on upper sideband only. 6415 could be "Radio Bluebell", a German pirate station that normally airs around 11:00 GMT. And the 6555 area should be devoid of English broadcast. Obviously books published at the end of last year like Passport And WRTH should be used as a guide only. If you're really hardcore, check out Glenn Hauser's World of Radio (http://www.angelfire.com/ok/worldofradio/).

Bas van Dam

Big QSL from the Netherlands Professor! I'm an electronics engineer. And I do antennas. Not royalty flagpoles. Love your radio series!


Hello Professor!

QSL from Halifax, Canada. HF has been dead here for the past couple of weeks except for a brief opening on 80 meters Friday night. Do you think the current prediction models for a highly active solar cycle have any creedance?

- Nikishka (in VE1 land...)


The Professor

Thanks for all the responses! It really makes spending all the time working on this project worth it for me. It’s great to know this blog series is being read and even appreciated. While I hope to pass on my personal passion for tuning through the short and medium wave bands, doing this has also been a learning experience and comments from some of you more experienced listeners is very helpful in that regard.

And boy, while I would love to see a big bright aurora some time (whenever I’m away from the city on a clear night, I’ll step out at least once or twice and look toward the north just to see if there might be one gracing the sky), the exact effects of auroras, sunspots, and space weather on radio transmission and reception in general seems a little complicated to my little brain. From what I seem to recall, propagation on some bands is improved and propagation is dulled on other bands during certain levels of activity out there. I have yet to read an explanation or report on these topics in language that I can clearly understand.

While I have bought the World Radio & TV Handbook a few times, the fluid and changing world of shortwave broadcasting times and frequencies can be tracked in a much more up to date fashion via the web these days. But there doesn’t seem to be any one source that serves as a guide, but between the bigger shortwave and DX sites and the many individual logs and blogs out there spending a bit of time searching seems to yield some good results. I do indeed look through Glenn Hauser’s expansive webpages for information and frequencies. When all else fails I’ve been doing advanced Google searches through his DX Listening Guides.

And I gotta tell you Ralph, your formula does make sense for a couple of those images I seem to have come across. While I didn’t hear spooky old Brother Stair at 6555, which you said could be an image of WWCR at 7465. What I did pick up was a USA Radio News Program, which according to their current schedule does INDEED play at that time on WWCR’s 7465 transmitter! While I can’t easily verify it, I suspect that you are also right about the Radio Austria International, and the Croatian station as well. Thanks a lot Ralph for some useful information. You are making me smarter, and I’ll keep that formula in mind when I come across image suspects on the BCL from here on in. The feedback I’ve gotten here from you and Dale as I’ve been doing this really has contributed to this whole series.

I really do like many things about the BCL radio, but I do hope that Tecsun takes on the complaints of many DXers and comes out with a dual conversion upgrade of the thing with a number of other improvements that would really make it the analog portable to get as an alternative to the many digital sets out there. Speaking of that, until I can get together the bucks for the Sony ICF-2010 one day I’m seriously considering picking up a Degen DE1103 (also known as the Kaito KA1103) to add a dependable digital receiver to my collection. I’ve read plenty of good to glowing reviews of the thing online, and I’m wondering if any readers out there have any personal experience with this radio. The Sangean ATS 505 I picked up a few years back has been a big disappointment. As I think I said before, every Sangean product I’ve ever purchased has let me down.

Anyway, my humble appreciation again for the comments. It is good to hear from you.


My pleasure, Professor.

It's easy to get lost in the science behind propagation, but there are a few simple rules of thumb you can use to help understand the basics. Solar Flux is related to the number of sunspots, and affects which frequencies are generally audible. Solar Flux doesn't generally go below about 70; if it's below 100, lower frequencies will work better than higher frequencies. If it's above 150, higher frequencies will open. The numbers vary, but in general there's an 11 year cycle, and you'll be more likely to see low numbers at the bottom of the cycle and high numbers at the top of the cycle. Right now we're end the bottom of a cycle, and the Solar Flux right now is 77, which means that lower frequencies work better. This is a great time to DX mediumwave. In about five years, we'll probably be near the top of the cycle, making the upper reaches of shortwave good for DXing (and sometimes this even extends into TV channels 2-6 and the FM band).

There's another number you can pay attention to, the K-index. It's released every three hours, and it varies between 0 and 9. If the K-index is 0 or 1 for a few periods in a row, you can expect to hear stations that are normally weak or in someway problematic at somewhat stronger levels. You may hear a few stations that are normally inaudible at weak levels. If the K-index is between 2 and 4, conditions are pretty much normal. If the K-index is 5 or above, there's a geomagnetic storm. The higher the K-index, the more disturbed conditions are. The more disturbed conditions are, the more likely you are to see an aurora. Auroras are caused by high levels of ionization in the ionosphere. Ionization is also what causes shortwave and mediumwave signals to reflect back to Earth. When ionization levels are high as reflected by a high K-index, signals closer to the polar regions are swallowed up by the ionosphere rather than reflected. So when the K-index is high, you will often find that stations you normally hear are inaudible, particularly ones from northern locations, and stations from tropical regions that are normally covered up are now audible. Occasionally, conditions are so stormy that all of shortwave will seem empty and blacked out for an hour or two. That's not happening so much now, but will probably happen more often in a few years.

You can find out these numbers in a few ways. WWV broadcasts them at 18 minutes past every hour. You can read the text of the WWV broadcasts at any time from the NOAA site. And you can get a graph of the K-index for the last 3 days from the NOAA site. There's even a browser extension for Firefox that continuously displays the numbers in your status bar.

This is a little longer than I intended, but the basic things to remember are 1) Solar Flux gives a basic idea of which frequencies work and which don't; higher numbers mean higher frequencies, and 2) the K-index is the current weather report, and higher numbers mean stormier conditions and more unpredictable reception.


Hrm, don't know what happened to my name there, but that previous comment about propagation was mine....


gracias for the link.


After reading your post, I watched this Gene Scott video on youtube: http://youtube.com/watch?v=J6Fqms_Iw8M

"Keep your *** **** opinions to yourself, you ******* from Australia!"

Now I know a bit more about what's on the radio. Your post made me curious enough to tune in to the Caribbean Beacon despite my previous rule of ignoring religious content on shortwave.

The comments to this entry are closed.