Return-Path: Received: (qmail 6066 invoked from network); 15 May 2001 14:02:55 -0000 Received: from unknown (HELO murphys-inbound.servers.plus.net) (212.159.14.225) by excalibur.plus.net with SMTP; 15 May 2001 14:02:55 -0000 Received: (qmail 12128 invoked from network); 15 May 2001 14:02:23 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by murphys with SMTP; 15 May 2001 14:02:23 -0000 Content-Transfer-Encoding: 8bit Received: from majordom by post.thorcom.com with local (Exim 3.16 #2) id 14zfIO-0006QE-00 for rsgb_lf_group-outgoing@blacksheep.org; Tue, 15 May 2001 14:55:28 +0100 X-Priority: 3 Received: from bob.dera.gov.uk ([192.5.29.90]) by post.thorcom.com with esmtp (Exim 3.16 #2) id 14zfIL-0006Q8-00 for rsgb_lf_group@blacksheep.org; Tue, 15 May 2001 14:55:25 +0100 X-MSMail-Priority: Normal Received: by bob.dera.gov.uk; (8.8.8/1.3/10May95) id OAA00886; Tue, 15 May 2001 14:58:49 +0100 (BST) Received: (qmail 14976 invoked from network); 15 May 2001 14:48:14 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from gauntlet.mail.dera.gov.uk (172.16.9.10) by baton.dera.gov.uk with SMTP; 15 May 2001 14:48:14 -0000 Received: by gauntlet.mail.dera.gov.uk; id OAA26466; Tue, 15 May 2001 14:43:14 GMT Received: from unknown(10.71.64.31) by gauntlet.mail.dera.gov.uk via smap (3.2) id xma026327; Tue, 15 May 01 14:42:35 GMT Received: from frn-gold-1.dera.gov.uk (unverified) by mailguard.dera.gov.uk (Content Technologies SMTPRS 4.1.5) with ESMTP id for ; Tue, 15 May 2001 14:37:04 +0100 Received: by frn-gold-1.dera.gov.uk with Internet Mail Service (5.0.1460.8) id ; Tue, 15 May 2001 14:29:10 +0100 Message-ID: <65AECDF1F89AD411900400508BFC869F9C04A2@pdw-mail-1.dera.gov.uk> From: "Talbot Andrew" To: rsgb_lf_group@blacksheep.org Subject: LF: RE: Is 0.5dB useful ? Listening tests Date: Tue, 15 May 2001 14:24:59 +0100 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.0.1460.8) Content-Type: text/plain; charset=iso-8859-1; format=flowed Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: 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 > > -- The Information contained in this E-Mail and any subsequent correspondence is private and is intended solely for the intended recipient(s). For those other than the recipient any disclosure, copying, distribution, or any action taken or omitted to be taken in reliance on such information is prohibited and may be unlawful.