[SEDXC] Interesting Phenomena. Worm hole entrance or strangepropagation?

[Jeff Carter]

We use the speed of light as a convenience and because it's the true
velocity in free space, but as you've pointed out RF doesn't travel at the
speed of light in atmosphere.  There's a velocity factor to consider for any
given transmission medium.

The ARRL Handbook used to cover this, but I don't know if it still does.  An
old copy might be of use.

When I read the original post, it sounded to me like multipath receive.  You
may recall back in the days of analog NTSC TV if there was an antenna
location near a mountain range or large buildings, there would be a
"ghosting" effect on the screen sometimes.  This was a phase difference
caused by the direct signal being received and then the reflected signal
from the obstruction being received milliseconds later.

The weather conditions could have caused the observed phenomena, and without
further data I'd have to assume that's what happened.  Broadcasters with
studio-to-transmitter links battle this situation sometimes.

Jeff

On Sat, Jan 1, 2011 at 11:18 PM, Tom W8JI <w8ji at w8ji.com> wrote:

> > pretty big storm front about half way between us at the time.  I just
> > can't
> > explain the delay in the signal.  It was about half a morse character (or
> > less)  at 25-30 wpm.  That would make the delay about half a second.
> > Maybe
> > my ears were off and the delay was say 100 mSec.  That would make the
> > distance 186000*.1 = 18,600 miles.  That is very close to the
> > circumference
> > of the earth.  WOW! ..
>
>
> I only know a little it about this, but one thing that jumps out is
> assuming
> the velocity of propagation through the ionosphere and atmosphere is unity,
> or the speed of light. If we assume radio waves travel as if in vacuum, the
> time delay seems unexplainable.
>
> EM waves propagating through water or through a plasma (or even air) are
> certainly slowed. The amount of slowing depends on the permittivity and
> magnetic inductive capacity of the media.
>
> Also, there are other modes through a plasma (the ionosphere is a plasma)
> than the normal EM wave propagation we expect. Slow-wave propagation
> through
> a plasma is pretty well known when working with plasmas, and I expect it
> occurs in the ionosphere also.
>
> I think there is a collision mode also, where the wave propagates very
> slowly via collisions between ions. Don't quote me on this though. :-)
>
> There is another effect that causes long delayed echoes. I knew a kid in
> high school who used to record and play back, at very low power into a
> dummy
> load, transmissions by his neighbor. He would be in his basement working on
> a project, walk over to his radio and push a button on his reel to reel
> tape
> recorder, and play back a delayed copy of his neighbor's transmissions.
> Somehow he had the reel to reel rigged to make a delay, probably an
> additional playback head downstream of the record head.
>
> The neighbor was so loud the kid could receive his neighbor over top of his
> own transmitter (because he transmitted into a dummy load and received on
> an
> outdoor antenna). His neighbor would go on and on at club meetings about
> the
> echoes he heard, and how his signal must have been bouncing off the moon
> and
> how sometimes it had a strange frequency shift to it.
>
> I always wonder, 45 years later, if that person has grown up and is still
> active....but with a voice fancy recorder system.
>
> 73 Tom
>
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