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Re: LF: 531 khz Faroe

To: [email protected]
Subject: Re: LF: 531 khz Faroe
From: "John P-G GM4SLV" <[email protected]>
Date: Tue, 26 Aug 2008 12:23:50 +0100 (BST)
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Mal wrote:

> This BC station on 531Khz is S9 with me daytime and not a trace of any
> sideband noise at this distance.

This is a shame, as it might imply that your receiving setup is not quite
up to the high standards you claim for it!

There is very evident sideband spreading on this signal, with detectable
artifacts well away from the nominal 5kHz bandwidth to be expected from a
MW station!

My spectrum analyzer plots show the signal to be very broad, of the order
of 30kHz or more, down to the -115dBm noise floor of the analyzer.

Obviously a receiver has a lower noise figure, and in a 250Hz CW
bandwidth, much lower signals can be detected, further away from the
carrier than this, out to 485kHz.

Observing the modulation depth shows that the postive going peaks approach
115% and the negative going peaks totally cut off the carrier a BAD THING.

This excessive negative going modulation is most probably the cause of the
wideband splatter.

I've received spectrum plots and listener reports from other stations,
including one in Belgium, which confirm my own observations.

I'll put the scans of the spectrum plots online later today if I get a
chance, along with comparisons of good stations (two in Scotland and one
in Norway) to show the problem in stark detail.



> I have a sea path to the Faroes, good reception.

But not THAT good, if you can't detect the spectral spreading of this very
poorly modulated signal.

Are you sure you're operating your receiving APPLIANCE correctly?

John



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