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.