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)
From: Chris
Sent: Thursday, March 03, 2011 7:55 PM
To: RSGB LF Group
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.
See the result and conclusion on my website http://qsl.net/g4ayt on the
bottom of page 1.
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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