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LF: LF Dopplergrams

To: "'LF Group'" <[email protected]>
Subject: LF: LF Dopplergrams
From: "Talbot Andrew" <[email protected]>
Date: Thu, 20 Apr 2000 11:25:34 +0100
Reply-to: [email protected]
Sender: <[email protected]>
Last night I tried to make a Dopplergram trace of a carrier transmitted
from Marco in a bandwidth of 0.12 Hz.  On looking at the plot this
morning I'm not too sure what to make of it an whether the results are
even genuine .  Firstly, the frequency seems too far out, centred at
0.04 Hz low and there is a wobble on the trace about 0.02 Hz wide which
might or might not be propagation effects.   Marco has not confirmed
what source he was using for the transmission.  Although he had said it
was going to be a Rubidium source I am surprised the frequency shift is
as high as that observed

Conventional Dopplergrams on 3.5 MHz typically show a few Hz shift
overnight plus a spreading of the signal, so a simple linear scaling
would appear to give the right order of frequency shift to that
observed. There was not a lot of spreading visible, but that may be
consistent with a single reflection from a moving cleaner layer.  But I
do not know enough about propagation mechanisms to know if simple
scaling is appropriate from 3.5 to 0.137 MHz

I'll send a copy of the dopplergram / spectrogram plot to anyone wanting

Another try tonight hopefully.

Andy      [email protected]  or   [email protected] over the Easter

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