Topband: LDE's & temporal dispersion

[Jim Jarvis]

With due respect to all comments, and the work of
Dicke, Penzias, et.al. ... (not to mention W8JI)...

I have heard LDE's and multipathing at various times
on 40m, in the now 47 years that I've been hamming.  
Typical multipathing results in (temporaly) offset CW signals, 
such that you can't copy them faster than 10-15wpm.  It's
probably on the order of 300mS or so.  Commonly heard on
JA's short path, plus skew path, around the equinoxes.

I have twice heard my own full call come back...the first as
WA2KHL, in 1962, after calling CQ at dawn on 7010.  Heard
"wa2khl k".  Speed was around 20 wpm, and it arrived right after
I switched to RX, so you figure the delay..maybe 4-5 seconds?  
And it had my characteristic bug-swing, so it was me.   
Second time was n2ea, and the delay was shorter..
maybe 2 or 3 seconds, and it was ALSO around dawn.  Both were
in the dead of Winter.  Dec-Jan.

In both cases, there was a definite softening of the waveform
edges...smearing of the signal, in time.

That said...the notion that signals can propagate for hours 
and then show up...and still be of a strength that is above
sky noise or rx noise....would seem to stretch the imagination.
i.e. it would be below Dicke's background noise predictions.

This time of year, however, with all the major contests behind us,
and Dayton, Friedrichshafen, and antenna projects ahead of us, a ham's
fancies tend to turn toward.....  you fill in the blank.

As for me, I'm going sailing....see ya in the fall!

N2EA
jimjarvis at ieee.org