Return-Path: Received: (qmail 20711 invoked from network); 22 May 2002 17:27:43 -0000 Received: from unknown (HELO murphys-inbound.services.quay.plus.net) (212.159.14.225) by excalibur.plus.net with SMTP; 22 May 2002 17:27:43 -0000 Received: (qmail 17184 invoked from network); 22 May 2002 17:27:28 -0000 Received: from unknown (HELO post.thorcom.com) (193.82.116.70) by murphys.services.quay.plus.net with SMTP; 22 May 2002 17:27:28 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.33 #2) id 17AZrK-0000c1-00 for rsgb_lf_group-outgoing@blacksheep.org; Wed, 22 May 2002 18:25:10 +0100 Received: from mta5-svc.business.ntl.com ([62.253.164.45]) by post.thorcom.com with esmtp (Exim 3.33 #2) id 17AZrJ-0000bw-00 for rsgb_lf_group@blacksheep.org; Wed, 22 May 2002 18:25:09 +0100 Received: from l8p8y6 ([62.252.233.57]) by mta5-svc.business.ntl.com (InterMail vM.4.01.03.27 201-229-121-127-20010626) with SMTP id <20020522172507.KJRK22320.mta5-svc.business.ntl.com@l8p8y6> for ; Wed, 22 May 2002 18:25:07 +0100 Message-ID: <000c01c201b5$c3b19a20$39e9fc3e@l8p8y6> From: "hamilton mal" To: rsgb_lf_group@blacksheep.org Subject: LF: bandwidth Date: Wed, 22 May 2002 18:25:38 +0100 MIME-Version: 1.0 Content-Type: text/html; charset=windows-1252 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.50.4807.1700 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

Some recent comments seem to indicate that all selectivity should be left to the FFT when using computer derived programs like ARGO and associated type programmes for narrow frequency modes like QRS.

My approach is to feed the RX audio to the computer sound card at the narrowest bandwidth possible, in the case of the pegelmessers at 20 hz b/w. When using conventional receivers with b/widths around 200 hz I then use an external audio DSP unit and again reduce the bandwidth to the narrowest possible. Weak signals stand out a lot better when using this method. On normal cw signals using the most narrow bandwidth possible, commensurate with speed, makes a big difference to hearing the signal. Signals that are barely audible with a 300 - 1000 hz filter are perfectly readable with a 20 - 50 hz filter, the signal over noise is improved dramatically.

The same applies to all modes of signal, minimum bandwidth to achieve the object.

This is normal commercial practice but some radio amateurs are still working in the dark.

G3KEV