Showing posts with label planes. Show all posts
Showing posts with label planes. Show all posts

29 Apr 2015

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.

27 Jun 2014

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..

24 Jun 2014

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.