More aircraft reflections on 6m WSPR

M0YOU (116km) has been spotted again on 6m WSPR at a strong -9dB S/N. What is interesting is that all his recent signals have shown multiple reflections off planes (up to 5 at one time in the 2 minute TX window) but, so far, just one successful decode. Clearly these planes need to be flying in the right direction for a successful WSPR decode to take place. The reflected signals are strong but the WSPR TX burst is too long. A shorter TX burst would be better for this propagation mode.

M0YOU - catching reflections off planes in the Heathrow stack?

I suppose the Doppler would be less of an issue on 10m but far more of an issue on 2m. G3WKW (134km) and I managed to exchange 2-way WSPR on 2m last year, but it took a whole day to catch that right moment as I recall. Also as you go higher in frequency, rig drift becomes far more of an issue, so it can be more difficult again. For 70cms WSPR this becomes super-critical and an external reference frequency is all but essential so that you can know your frequency precisely.

G4FGJ (44km) has spotted me this afternoon but I think this was plain simple tropo as no Doppler was apparent. He was very strong with me at -2dB S/N.

6m - G0OQK and aircraft

G0OQK (98km) is coming in here regularly today on 6m WSPR. Looking at his traces on my WSPR screen, there is clear evidence of airplane involvement:  most 2 minute transmissions appear with 2 or 3 Doppler shifted lines, suggesting planes along/crossing the path between us.

What I cannot be 100% certain of is if the path would "work" without airplanes As all successful decodes seem to be when there is evidence of planes, I think the path is only possible when there are planes, but honestly I am still unsure.

The last decode at 1124z had drift (probably Doppler) of 3Hz, which is a lot. Sometimes the drift/Doppler was 0Hz. So far this morning Nick G0OQK has been seen 9 times. The other Nick G4IKZ (18km) has seen me countless times, but he is very local.

Interestingly, G4IKZ had 0Hz Doppler/drift on all his spots overnight of G0OQK. The distance is 83km with crossed polarisation (I think).  Perhaps this is evidence of pure tropo? At night few/no planes etc..

G0OQK by pure tropo?

The most recent transmission from Nick G0OQK (98km) was at 1854z. Unlike earlier transmissions this was received as a single straight line on the WSPR software screen with not even a hint of aircraft reflections. I wonder if this was pure tropo?  His signal strength was -20dB S/N.

The alternative explanation is this was just a single plane flying in such a direction that there was no Doppler on the signal. I think this means a plane exactly crossing the path between us. I need to dig out that software G3WKW mentioned to see when planes are optimally placed. A reminder it was http://www.airscout.eu.