Return-Path: Received: (qmail 22114 invoked from network); 22 May 2000 18:47:35 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by grants.core.plus.net.uk with SMTP; 22 May 2000 18:47:35 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.02 #1) id 12tx8R-0003Qc-00 for rsgb_lf_group-outgoing@blacksheep.org; Mon, 22 May 2000 19:41:03 +0100 Received: from cmailg6.svr.pol.co.uk ([195.92.195.176]) by post.thorcom.com with esmtp (Exim 3.02 #1) id 12tx8P-0003QX-00 for rsgb_lf_group@blacksheep.org; Mon, 22 May 2000 19:41:02 +0100 Received: from modem-164.chromium.dialup.pol.co.uk ([62.136.23.164] helo=thebitch) by cmailg6.svr.pol.co.uk with smtp (Exim 3.13 #0) id 12tx8N-0004ho-00 for rsgb_lf_group@blacksheep.org; Mon, 22 May 2000 19:40:59 +0100 Message-ID: <006101bfc45f$0d56e900$755d883e@thebitch> From: "Des Kostryca" To: "LF-Group-Reflector" Subject: LF: Re: Morse tones / filters etc. Date: Mon, 22 May 2000 19:30:45 -0700 MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2615.200 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: 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.