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LF: RE: Is 0.5dB useful ? Listening tests

To: [email protected]
Subject: LF: RE: Is 0.5dB useful ? Listening tests
From: "Talbot Andrew" <[email protected]>
Date: Tue, 15 May 2001 14:24:59 +0100
Reply-to: [email protected]
Sender: <[email protected]>
I've often thought that a listening test amongst amateur radio operators
under precisely controlled conditions would throw up some interesting
results.  Especially amongst the expert contest operators and DX
chasers.

Listening to pre-recorded SSB voice and CW signals with variable and
accurately measured S/N and QRM levels would be the simplest way .   To
keep the test as accurate as possible, the messages would need to be
replayed on standard equipment - say at a rally or convention somewhere.

The main problem with this method, as I see it, is that CW each operator
has their own preferred CW pitch and some like to be continually
shifting this (professional intercept opertors do anyway), and this
would not be possible with pre-recorded messages replayed as audio.
Also, shifting SSB tuning from optimum can help resolution in some
cases. So some means of injecting precise noise and QRM levels into a locally
generated signal, to be received off air , would be a better solution,
but more difficult to arrange with laboratory prescision at a large
event.

It can be done though....   Pre-recorded voice / CW signals could be
mixed with known and variable levels of noise and standard reference QRM
sets, then upconverted, allowing operators to twiddle to their taste.

Andy  G4JNT

Even with analogue modes this sort of improvement can be much more useful than many people would think when the signal is close to the noise. I would always go for any improvement, no matter how small, as they all add up.
Mike, G3XDV (IO91VT)
http://www.lf.thersgb.net



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