Talk:Long delayed echo

Possible explaination
I have encountered LDE's on some DX stations (VE2 and western EU) from Australia over the past 6 years or so... ie not my own echo's, but delays between the DX main signal and then replications of their signals..

Being an engineer (PE) with a very 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% to 2% of the speed of light or less...  A classical microwave worked example is referred below.

I am confident the ionosphere can 'fabricate' a sizable waveguide style duct over short periods. While this would and could easily explain a single signal delay, some discontinuity in the 'ionospheric waveguide' could generate return loss blips... hence echo's.

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 phase velocity effect in practice on the HF bands. (UNSIGNED by 203.185.214.196)

TO OP: Fascinating! — Preceding unsigned comment added by 91.190.161.223 (talk) 08:05, 5 February 2020 (UTC)

Additional TO OP: Do you have any data? I would be intrigued to see it if so. The possibility of "slow light" in a waveguide could account for other atmospheric anomalies as well. — Preceding unsigned comment added by 91.190.161.223 (talk) 10:24, 15 February 2020 (UTC)

New event
On Nov. 27th there was a new evant of an LONG-DELAY RADIO ECHO. Reportetd here http://www.spaceweather.com/ —Preceding unsigned comment added by 87.189.183.33 (talk) 14:55, 1 December 2010 (UTC)

Non-technical point of view
I come to this by way of a 5 page description in Paul Watzlawick's 1976 book, "How Real Is Real," in which he uses the 1927-1928 Eindhoven events as an example in his discussion of communication theory. Specifically in his chapter on the difficulties that can be anticipated with extraterrestrial communications. It is the Bricewell probe theory. And, in Watzlawick's extensive footnotes there is a citation to an April 1973 article in Spaceflight, the monthly magazine of the British Interplanetary Society, by Duncan A. Lunan, titled, "Space Probe from Epsilon Boötis." This would be an acceptable citation to satisfy Wiki's need to verify, in support of a more detailed discussion of the specific 1927-1928 LDEs as a possible Bricewell probe.

Two points. 1) There is no indication that the Bricewell probe theory is offered to explain every long delay echo, and 2) regarding the 1927-1928 LDEs, Watzlawick states, "too many pieces of the puzzle fall into place for Lunan's hypothesis to be dismissed out of hand." What to do? —Preceding unsigned comment added by Tomwfox (talk • contribs) 04:58, 2 December 2010 (UTC)

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Category "Unexplained"?
The article contains many well sourced explanations. It's unencyclopedic to promote a WP:SENSATIONAL "mystery" angle. - LuckyLouie (talk) 14:40, 14 January 2020 (UTC)


 * Agree No reason for this category. David J Johnson (talk) 21:32, 14 January 2020 (UTC)

Why 2.7 seconds?
The 2.7 seconds is not explained. Is it to filter out direct reflections from the Moon?

Why doesn't it contain delays up to close to, but slightly below the Moon reflection time?

I think this article should contain some information about it.

--Mortense (talk) 09:18, 29 June 2020 (UTC)


 * 2.71 seconds is the maximum EME round trip time, when the moon is at apogee. At perigee the delay would be 2.38 seconds.  Echos of shorter delays are explained in the ARRL reference link:
 * Echoes less than 2.7 seconds are likely caused by objects that are nearer to the Earth, for example, natural objects like the ionosphere and manmade objects like aircraft.
 * 73. ChrisRuvolo (t) 23:17, 2 May 2023 (UTC)

Ionization Ducting
What is that? Sounds like a good subject for a new article. — Preceding unsigned comment added by 108.54.109.52 (talk) 21:38, 18 December 2023 (UTC)