I have seen several theories for LDE's. The most plausible was a Ph.D.
thesis done at Cal Tech, I believe, back in the mid-70's. I wish I had a
copy of it. A fellow grad student in radio science at the University of
Illinois lent me the paper to study while I was working on my Masters in
that subject.
The theory was an EM wave coupling into a slowly moving mechanical
(acoustic) wave in the ionosphere under the proper conditions. The theory
involved much plasma physics and the "proper conditions" involved a
magnetic anomaly. The acoustic wave would travel a considerable distance
at a much slower velocity than that of light and then re-couple back into
an E-M wave.
The student who wrote the thesis did extensive testing to attempt to
verify his theory and actually produced quite a bit of evidence to back
it up. He measured quite a few LDE's under the conditions he specified
would produce them. I believe the student was also a ham.
I thought that was a much more realistic theory than LDE's as a result of
reflections from the earth's Lagrange points, which could also have some
remote possibility of occurring.
Then again, [joke] it could be a chronosynclastic infundibulum. :-)
73, Zack W9SZ
On Wed, 14 Jan 2004, K4SB wrote:
> > Back in the late 60's I heard an LDE that had about a 10 second delay and
> > was a repeat of everything I and the station I was working sent for about
> > 3 minutes. We were both pretty freaked out by it. I've heard others,
> > both longer and shorter delays, but nothing like that. I wish I'd
> > recorded it.
> >
> > 73, Zack W9SZ
>
> OK, let's think about it. Radio waves travel at the speed of light,
> and a 10 second delay would translate to about 1.86 billion miles
> before it was again heard. That is approximately the distance to the
> Planet Saturn, or assuming an Earth orbit, a complete round trip 7,410
> times.
>
> You could assume a large dish antenna with 50 db of gain, and a loss
> of 1 db per trip, and the signal would be in the mud on the 148th
> trip. That would leave approximately
> 7262 more trips around the Earth until it was received and heard. Not
> to mention the vast improvements in receiver noise floor in over 40
> years.
>
> Tape recorders have been around for a long time. So has elementary
> math. Recorders change with time, math doesn't.
>
> In no way do I mean to doubt Zack's word about it, but it simply is
> not possible as an LDE.
>
> On my own recollection of received LDEs the longest I ever heard was
> the letter B of my call at about 35 wpm, and that was also on 10
> meters.
>
> I leave it to someone else to figure the gain and power needed to
> bounce a HF signal off Saturn, which is actually twice the distance.
> Even our best orbiting telescopes are not capable of that.
>
> 73
> Ed
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