Interesting WSPR Doppler

K6PZB and I have been running WSPR on 6M, 2M and 432.3 MHz lately. To do this we both operate with external OCXO master oscillators on our IC-706 WSPR radios.
Our stations are about 5 miles apart but K6PZB is located on the wrong side of a hill on the western end of this E-W path. This makes it particularly interesting
for examining Doppler from aircraft flying in our region.
We do see Doppler on 10M through 430 MHz but 2M seems particularly good. The Doppler does not seem to cause WSPR any problem. We decode fine through the worst of it but the waterfall is fairly interesting to look at. Attached is an image showing several transmissions from n6gn as received at k6pzb. Doppler is obvious and more than one aircraft and aircraft closing at different rates can be seen. Combined with the amplitude information available, some of it may be coming from quite a ways away, perhaps even the San Francisco Bay Area which is about 60 miles to our south.
Note the one multiple Doppler 2 minute interval. If you can, suggest a situation that would have produced it. To date, we haven't seen any other instance of it and as yet have no explanation of the mechanism.

Glenn n6gn

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