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Thanks again Andy and Markus,
Yes, my feeling is that the reflective
wave shift is due to doppler as the layer changes height. We need to try it
again over a longer period. It is true there are a lot of aircraft between us,
but would the result have been so smooth?
Has this effect been seen on 137kHz? The info I
have seen on near vertical incidence/reflection suggest it should.
Any thoughts on this appreciated, thanks for taking
the time to comment.
Chris, G4AYT.
----- Original Message -----
Sent: Thursday, March 03, 2011 8:40
PM
Subject: Re: LF: Topband Test
No, it definitely is due to ionospheric shift.
30m/s is no big deal over the period of the day/night
transition. 30 minutes at that speed would be a mean change in
height of 54km. Not unrealistic for an E layer
(??) height of 120km
Try to find a copy of G3PLX's article
'JNT
On 3 March 2011 20:19, Markus Vester <[email protected]>
wrote:
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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