Hi Conrad,

On 7/8/2019 18:29, Conrad PA5Y wrote:
In fact Martin, sometimes they clearly AP reflections are but often they are 
not. They have no discernible doppler slant at all and appear to be a fixed 
offset and have me completely puzzled. I regularly see 2 or 3 'ghost' signals 
between 6 and 20dB lower in amplitude than the main signal on 2m from stations 
with 100W to a 9ele or more. Stations can be several hundred km away from me. 
The offsets vary between 70-150 Hz and can be positive or negative.  In order 
to have a doppler shift something must be moving and with an offset of 100Hz or 
more quite quickly. You would think therefore that the frequency offset would 
change and it often does not but remains static for several periods and then 
just disappears. How on earth can this happen? I have no reasonable explanation 
for it but I assure you it is real.

Aircraft scatter on 6m occurs of course but not so often, however during 
intense Es events sure enough I also see these ghosts on 6m and again no shift. 
It really is very puzzling indeed.

Evidently what's puzzling you is Doppler shifts that remain nearly constant for a minute or so. Aircraft at 10,000 meters can be line-of-sight visible at distances up to several hundred km. With typical aircraft speeds, in such cases the geometry for bi-static reflections will not change much over a minute. So the Doppler shift can remain nearly constant. Does this not make sense?

        -- Joe, K1JT


_______________________________________________
wsjt-devel mailing list
wsjt-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/wsjt-devel

Reply via email to