Return-Path: Received: (qmail 12860 invoked from network); 16 Apr 2001 09:14:23 -0000 Received: from unknown (HELO warrior-inbound.servers.plus.net) (212.159.14.227) by excalibur.plus.net with SMTP; 16 Apr 2001 09:14:23 -0000 Received: (qmail 5691 invoked from network); 16 Apr 2001 09:14:14 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by warrior with SMTP; 16 Apr 2001 09:14:14 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.16 #2) id 14p4z6-00010V-00 for rsgb_lf_group-outgoing@blacksheep.org; Mon, 16 Apr 2001 10:07:48 +0100 Received: from cmailg5.svr.pol.co.uk ([195.92.195.175]) by post.thorcom.com with esmtp (Exim 3.16 #2) id 14p4z2-00010Q-00 for rsgb_lf_group@blacksheep.org; Mon, 16 Apr 2001 10:07:44 +0100 Received: from modem-60.percula-clown.dialup.pol.co.uk ([62.137.49.188] helo=g3aqc) by cmailg5.svr.pol.co.uk with smtp (Exim 3.13 #0) id 14p4ya-0005G7-00 for rsgb_lf_group@blacksheep.org; Mon, 16 Apr 2001 10:07:16 +0100 Message-ID: <001001c0c64c$3aed0580$bc31893e@g3aqc> From: "Laurie Mayhead" To: rsgb_lf_group@blacksheep.org Subject: LF: DFCW, an idea. Date: Mon, 16 Apr 2001 09:06:19 +0100 MIME-Version: 1.0 Content-Type: text/html; charset=windows-1252 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.50.4133.2400 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: Content-transfer-encoding: 8bit

Hi all,

I am very keen on exploiting DFCW to its limit (after all its easy to implement) but it still needs to be speeded up. Because of the lack of timing of the FFT bins they tend to become blurred and it is neccessary to leave large gaps between elements of a character with consequent waste of time.This is even more true with QRSS. With DFCW the frequency change between dots and dashes adequately separates them. Currently on T/A tests I have been using a 50 sec. period, 30 secs constitutes the transmitted element and 20 secs the gap ! What a waste of time. Looking at the signal on my monitor (also see Uwe's pics,thanks Uwe) these gaps are still poorly defined. I have thought about synchronising the Tx and Rx using some form of universal time signal but 1) this might be thought as cheating

and 2) the path variations, phase changes etc would be a problem. So my point is WHY BOTHER ! would it not still be possible to read the message without these gaps (they are hardly there anyway). For A to Z there is not much of a problem since there are only two adjacent elements ie 2 dots or two dashes, except for JO S H .But the numbers are a bigger problem. Anyway, crazy perhaps but any ideas ? 73s Laurie.