Several people have e-mailed me suggesting that the weird echo I have been hearing on shortwave broadcast stations is in fact one of the fabled "Long Delayed Echoes" that radio amateurs have been hearing intermittently since about 1927. I was skeptical at first, but -- at least in the case of the Radio China signal -- I think LDE caused by the signal going around the globe several times does explain what I've heard. Each trip would add a delay of about .133 seconds, and that seems to match what we hear in my recording: http://soldersmoke.blogspot.com/2014/08/strange-echo-on-china-radio.html Compare that with what K9FIK recorded on 10 meter SSB (thanks Stephen!): http://swling.com/blog/2013/10/hearing-the-speed-of-light-dx-double-echo/ (you can listen to the audio on this one). It sounds very similar. If this is in fact LDE, I'm lucky -- this is pretty rare. And it is a eerie that I first heard it on on Regen receiver from the 1920s! Above is a picture of the regen used to study the FIRST LDEs. See: http://folk.uio.no/sverre/LDE/
In response to popular demand, "SolderSmoke -- Global Adventures in Wireless Electronics" is now available as an e-book for Amazon's Kindle.
Here's the site:
For the print version:
For shipping from a printer in the U.S. (probably better for N. American buyers) Click here: SolderSmoke USA Version
For shipping from a printer in the UK, Spain, or the USA (probably better for UK and other European buyers)
Click here: SolderSmoke EU Version
The two versions are identical, except for a minor difference in the paper used. That's why the prices are a bit different.
Bill's OTHER Book (Warning: Not About Radio)
Click on the image to learn more
W4HBK's QRSS Grabber: The Amazing Pensacola Snapper (Live!)