It is not unusual for me to hear some sort of multipath propagation on 20m late in the afternoon here in Arizona when beaming to Japan (single receiver and 4 element yagi with a good F/B ratio). The disparity in arrival time is often enough to make signals totally unreadable at CW speeds of roughly 25 WPM. The middle of a character or even a word sometimes just sounds like a continuous carrier. This might go on for an hour or more until one of the paths disappears. I have on two occasions this winter even heard three different arrival times for the same signal, which was very weird and I wish I had recorded it. Given the differences in path length necessary to generate that kind of delay I make no claim regarding the cause ... only that I have clearly heard it several times.
In any case, if such delays are enough to blur 25 WPM CW, they would be enough to be easily noticed in static crashes. Of course, that still requires some sort of polarity disparity to create the effect observed by Mr. Zilmer.
73,
Dave AB7E
Stephen W. Kercel wrote:
Recall that radio waves move at 3 x 10^8 meters per second. If you look
at multi path propagation at HF radio waves over intercontinental
distances, and suppose that your two receivers were responding to two
different signals taking two different paths, the differences in time of
arrival of the different signals would be 1/10000 second or less.
... the delay is many orders of magnitude too short for your internal cognitive processes to
detect the difference in arrival time of RF wave fronts.
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