LDEs, "Long Delay Echos"

For Rashid Faizulin's LDE data click here

Sometime during the mid '60's there was an article in QST magazine about "Long Delay Echos".

It was about a study being done at Stanford on this phenomenon from the standpoint that it was probably an unknown mode of ionospheric propagation.  Basically, there have been from time to time reports by radio receivers of hearing a "delayed echo" broadcast of particular radio signals.  The "echo" signals were reported to often be quite strong, sometimes only maybe 15db lower than the primary signal.  The time of the lag varied from a fraction of a second, all the way up to (see below) 5 MINUTES !

It is fun to conjecture that instead of being a mode of ionospheric propagation that it could be caused by some object "repeating" the signals, rebroadcasting them.  With a delay of 5 minutes of course that would be a total distance representing 2/3 distance of the earth to the sun, or 0.6 AU.   Assuming it was an actual rebroadcast of course the distance to the repeating object would be half that, or 0.3 AU.

But the study focused on the more probable cause of ionospheric propagation.

I myself heard one on 80meter CW, with a lag of around 20 seconds which would still be a respectable and apparently inexplicable distance.   It persisted for less than a minute, if I recall correctly. I wrote to the study and reported my observation.

I just did a search on Yahoo and turned up what looked like a bibliography reference from QST,but it was a broken link.  However, I'm sure someone can find the article.  If you DO, please email me and let me know, maybe we could then expand this section.

For even wilder conjecture, click here.

            -Chuck, K1OM 9/14/97

The following is a copy of a newsletter I received (it's postmarked from Palo Alto 25 Aug 1969)

from

Mike Villard, W6QYT, Radioscience Laboratory, Stanford University, Stanford, California 94305

LDE REPORTERS' NEWSLETTER

August 1969

    The purpose of this letter is to thank all those who have so kindly contributed LDE reports, and to bring them up to date on developments.  Remember, if any of you hear LDE's, or in chatting with other's happen to hear the effect mentioned, please drop us a line, as more information is still clearly needed.

    The jigsaw puzzle is definitely not solved yet.  A capsule report would be: "the plot thickens!"   Reports have come in spaced in latitude from Canada to Peru; in longitude from Libya to the Marshall Islands, with delays ranging from 1/2 second to 5 minutes !   (Believe it or not, there are now two reports of these super-long delays).   The operating frequencies at which echoes have been reported range from 810 kHz through 144 mHz, including every amateur band in between.  The dates of occurrence of incidents run from 1932 through just last week.  The total number of useful reports now adds up to somewhere around 48.

    Preliminary statistical analysis of these reports suggests that there are two main categories of echoes, one of which may be explainable in terms of retardation at the ionospheric "critical frequency."   The other (and the more frequently occurring one) tends to occur at the time of opening or closing of transmission at a given frequency, when conditions are good for long distance propagation.  The latter echoes seem in general to occur at times of low magnetic activity.

    There seems to be little doubt that many of the reports describe a real effect of ionospheric origin, and therefore scientifically interesting.  However, three psychologists who have been consulted claim that subjective origin of at least the shorter-delay echoes is a definite possibility.  It appears that at least some reported echoes may have been generated within the listener !

    There are two reports of echoes at frequencies not normally propagated in the ionosphere - namely 50 and 144 mHz.  These are particularly baffling.  Similarly, the two broadcast-band reports are fascinating.  We also have reports of delays observed at 2 mHz.

    We are hoping to publish a summary of the reports soon; but we wanted to make this interim report available to contributors, asoon as was feasible.

    Thanks again for your help.

                                        Mike Villard, W6QYT

                                        Radioscience Laboratory

                                        Stanford University

                                        Stanford, California 94305

Back to chuckg.com