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Hi Chris, thanks for sharing this unusual
observation.
From your screenshot, the split was up to about
0.35 Hz, or 0.2 ppm of 1.8 MHz. Interpreted as Doppler, a reflector
would have to move at least 30m/s radially from your baseline. This seems a
bit fast for an ionospheric day-to-night shift.
Another possible explanation could be airplane
scatter. Large airliners are known to have a large radar cross section
at HF. Seeing that on 160 m may seem extreme, but considering the
wingspan of an A-380 (80 m), half-wave resonant scattering is a very
real possibility. The downward slope of the Doppler shifted
frequency would also be indicative of an object passing by at constant
linear velocity.
Best 73,
Markus (DF6NM)
Sent: Thursday, March 03, 2011 7:55 PM
Subject: LF: Topband Test
Hi All,
Yesterday evening Pete, M0FMT, transmitted QRSS on
topband for a test. An unexpected effect was noticed with the trace splitting in
two. Nothing new or 'earth shattering' I expect, but new to us and worthy of
further experimentation.
I have never seen this effect on 137, even with
quite strong audible signals, maybe others have.
Vy 73,
Chris, G4AYT, Whitstable,
UK.
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