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![Previous (earlier) Story](/images/sty-down.gif "FCC Releases Post-Katrina Order, "Final Rule""){kind=small} Previous: FCC Releases Post-Katrina Order, "Final Rule" |  Next: The K7RA Solar Update |
By Stan Horzepa, WA1LOU
Contributing Editor
July 13, 2007
This week's installment of Surfin’ echoes last week’s installment, which was all about long-delayed echoes (LDEs).
The Surfin’ mailbox received a lot of e-mail in response to last week’s installment about long-delayed echoes (LDEs).
David Burger, VK2CZ, wrote to Sverre Holm, LA3ZA, whose LDE findings on his Mystical delayed radio signals received in Oslo Web page were last week’s featured Surfin’ Web site. David also copied me and wrote, “I’ve been licensed here in Australia since 1974 and have encountered LDEs around 1977/1978 on the 15 meter band. In more recent times, I currently use a ‘very, very’ large 10 meter antenna array and have encountered LDEs on some DX stations (VE2 and western EU) from here over the past six years or so, i.e., not my own echoes, but delays between the DX main signal and then replications of their signal. These types of signals were last heard in December ’06 during the ARRL 10 Meter Contest I did. Note that I didn’t describe the signals, but you can see what I did.
“Being an engineer (PE) with a very pragmatic and practical bent, I simply put this down to the effects of signal progression in a waveguide where it is possible to have a signal moving through a waveguide down to 1-2 percent of the speed of light or less. These are all classical worked examples in microwave handbooks where the signal frequency is near the cut-off frequency limit for a waveguide.
“But I am very confident the ionosphere can ‘fabricate’ a sizable waveguide style duct over short periods and while this would and could explain a single signal delay, some discontinuity in the ‘ionospheric waveguide’ could generate return loss blips and, hence, echoes. I’ve no way to test this idea, but maybe info from ionosondes might help explore it. (See this figure.)
“Anyway, I figured I’d share my idea with you as I sort of took this for granted for the past 25 years that every engineering student who studied microwaves could see this effect if practice on HF.
“The idea of unknown aliens or X-Files may appeal to some, but after being immersed in engineering forensics for many years, most things can be explained. Anyway, it makes sense to me.”
Sverre Holm, LA3ZA, responded to David and carbon-copied me:
“Thanks for your interesting info on possible LDEs. I have never heard any myself, except for the echoes I describe here. Here I recorded JA3YBK coming in simultaneously over three different paths, which most likely are short-path, long-path and short-path with an extra trip around the Earth. Of course, this is not an LDE, but rather short-delayed echoes, but they are still interesting.”
Sverre added, “This is a topic with a certain aura of mystique around it, and a perfect topic for combining my radio amateur interests with my professional interests as well as with an interest in history.”
Terry Glagowski, W1TR, e-mailed the following, “I had the experience of an LDE back in the mid-1990s, maybe about 1994 or 1995. I was in Spokane, Washington, and it was late evening, not quite midnight talking to some W6 and W7 stations in California, Oregon and Washington on 160 meters, and I heard the LDE echo on my own transmission…about 1/3 second.
“I also tried it on 75 meters and the same thing happened! The other stations could not hear echoes of my signal or theirs. This went on for about an hour and then disappeared altogether, and I have never observed it since!
“I wrote to the ARRL describing this, and several possible explanations were given from different articles available at the time. The most likely explanation was that my signal followed a discontinuity in the magnetic flux lines down to the Southern Hemisphere and bounced back from there. That would explain the time of 1/3 second, but I didn’t do sufficiently precise or formal recordings/documentation of the phenomenon to go any further with it…too bad! Also, there was no Doppler shift that I could discern.”
Dave Newkirk, AB2WH, e-mailed the following update, “Although Bill Continelli’s installment #31 of ‘The History of Amateur Radio’ says ‘After the early 70s, reports of, and interest in Long Delayed Echoes diminished. Today, they are just a question mark in amateur radio history,’ QST told a different story in O. G. Villard, Jr’s, W6QYT, ‘The Magnetospheric Echo Box -- A Type of Long-Delayed Echo Explained,’ [October 1980, p 11].
“Also, my father (W9BRD) and several coworkers heard LDEs on a State Police interzone (shortwave CW) circuit just below 3 MHz in the 1960s. I think he mentioned that incident in his ‘How’s DX?’ QST column circa 1970.”
Finally, Whitey Doherty, K1VV, wrote, "We have experienced LDEs in several contests with our signals on CW coming around 1/7 of a second later. Confused me the first time I heard it. We have worked some DX during contests that the same thing happened. It seemed like their CW signal was coming from several directions at once with delays and was almost impossible to copy.
“I remember hearing about an LDE incident many years ago, must be at least 40 years ago, when TV channels went off the air at midnight. Someone said a program showed up on the screen, a snowy picture, but it was a broadcast from six years previously. It lasted several minutes. Can’t recall where or exactly when I heard that or read it.”
I replied to Whitey that I thought I had read about it in one of Frank Edwards’ Stranger Than…books.
Until next time, keep on surfin’.
Editor’s note: Believe it or not, Stan Horzepa, WA1LOU, prefers non-fiction to fiction because the truth is stranger than fiction. To communicate with Stan, send him an e-mail or add comments to his blog. By the way, every installment of Surfin’ is indexed here, so go look it up (whatever it may be).
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