Return-Path: Received: (qmail 8484 invoked from network); 22 Mar 2003 09:06:33 -0000 Received: from netmail01.services.quay.plus.net (212.159.14.219) by mailstore with SMTP; 22 Mar 2003 09:06:33 -0000 Received: (qmail 2778 invoked by uid 10001); 22 Mar 2003 09:06:33 -0000 Received: from post.thorcom.com (193.82.116.70) by netmail01.services.quay.plus.net with SMTP; 22 Mar 2003 09:06:33 -0000 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 4.12) id 18wewO-0004u8-00 for rsgb_lf_group-outgoing@blacksheep.org; Sat, 22 Mar 2003 09:05:24 +0000 Received: from [62.253.162.45] (helo=mta05-svc.ntlworld.com) by post.thorcom.com with esmtp (Exim 4.12) id 18wewJ-0004tz-00 for rsgb_lf_group@blacksheep.org; Sat, 22 Mar 2003 09:05:19 +0000 Received: from mike1 ([80.4.107.45]) by mta05-svc.ntlworld.com (InterMail vM.4.01.03.37 201-229-121-137-20020806) with SMTP id <20030322090519.OXWQ310.mta05-svc.ntlworld.com@mike1> for ; Sat, 22 Mar 2003 09:05:19 +0000 Message-ID: <000a01c2f052$5c342160$2602a8c0@WorkGroup> From: "Mike Dennison" To: rsgb_lf_group@blacksheep.org References: <5.1.0.14.0.20030320183946.0260e158@gemini.herts.ac.uk> <000601c2f033$e413b3d0$d6e136d2@bob2l2u6k2n1g3> Date: Sat, 22 Mar 2003 09:06:43 -0000 MIME-Version: 1.0 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 Subject: LF: Re: Selection of spot frequencies for DX Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, hits=-9.8 required=5.0tests=QUOTED_EMAIL_TEXT,REFERENCESversion=2.50 X-Spam-Checker-Version: SpamAssassin 2.50 (1.173-2003-02-20-exp) X-SA-Exim-Scanned: Yes Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rsgb_lf_group-outgoing@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false > I originally thought that 137.7000 kHz was clear of QRM in this corner of > the world, however lots of capture time on trying to find a UA9OC signal > (with success on 13 March) found a weak QRM typically 0.35 Hz higher than > where I think is spot on 137.7000 kHz. > So my suggestion for selecting frequencies for long haul DX between amateur > stations is to avoid multiples of 50 or 60 Hz (50 Hz mains being used in > some regions, 60 Hz in others). 137.7100 kHz is an example of being clear > of 50 Hz harmonics, whereas 137.7000 kHz is dicing with the 2754th harmonic > of 50 Hz, plus or minus some tolerance for the national grid. > 73, Bob I can confirm that 137.71000 is clear in the UK, but the situation varies around the world because of various Loran systems, and spurious emissions and mixes from commercials. In practice, even a 120s dot window has a viewable width of 1.5Hz so the real answer is for a DXpedition to be precise about its frequency (which can be advertised in advance and objected to, if necessary) and for callers to spread out. A pre-posted, or live, screen shot will show callers which frequencies to avoid. Mike, G3XDV http://www.lf.thersgb.net ====================