Message-ID: <006101bfc45f$0d56e900$755d883e@thebitch>
From: "Des Kostryca" <des@kostryca.freeserve.co.uk>
To: "LF-Group-Reflector" <rsgb_lf_group@blacksheep.org>
Subject: LF: Re: Morse tones / filters etc.
Date: Mon, 22 May 2000 19:30:45 -0700
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Kevin Ravenhill wrote:


> Has anyone experimented with phase shifted / delayed audio, i.e. with
"raw"
> audio fed to one half of the headphones and a (variably) phase-shifted /
> delayed version fed to the other half?
>
> Kevin
> G1HDQ

Greetings all,

   A very interesting discussion and I recall the above description comes
very close to that given by F. Charman (G6CJ) and R. Harris (G3OTK) in their
Rad-Com article "Subjective selectivity and Stereocode" (September 1975) in
which a system of all-pass filters is used to frequency/phase shift the
audio spectrum in such a way as to present the operator with a "3D" audio
image in which lower frequencies are more to the left and higher frequencies
to the right. The intention being to make CW copy better in the presence of
QRM, QRN etc. The article went on to describe a full circuit design known as
the "Stereocode Processor" which has been emulated many times since in more
recent articles.

Many of the more recent articles have tended to over simplify the original
design by feeding the audio through a pair of passive filters (one L.P.F.
and one H.P.F.) and feeding the filter o/p,s to the left and right
headphones. I am not sure how much this helps to the discussion but its a
very interesting article :-) Just for the record I have one ear (left) which
has a poor response to higher audio frequencies and when listening on the
loudspeaker I do find that rotating my head gives me an optimum listening
position when signals are marginal or noisy.

Regards to all on the list.

Des.

Des Kostryca (M0AYF)
GQRP Num. 9788
136 kHz LF operator.