Doppler Shift From Aircraft Resulting in Miltipath

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Doppler Shift From Aircraft Resulting in Miltipath
Image icon 2009 01 10 WSPR Doppler Graphic.JPG235.82 KB

This concept was originally broached by W3CSW a couple months ago. Apparently, on hi angle skywave paths where stations are less than 30 miles apart, reflections off of moving aircraft result in multipath. Attached is a graphic of a simal cast by W3CSW and N1SZ both near my location in Columbia, Md. Another nearby station WB3ANQ does not exhibit such multipath.

When the multipath is severe decoding of the transmission is not possible. N1SW and W3CWS transmitted continuously last Saturday morning for about 1 hour. The attached file covers the first half hour. Both stations were in a deep fade at the start of the sample and went into another fade at the end. There are 3 major airports in this area. I suspect aircraft flying north of Washington National either landing or taking off to be the players.

I’d be interested in thoughts anyone else might have on the subject….

73 /Dave Larrabee K1BZ