Return-Path: Received: (qmail 7962 invoked from network); 6 Mar 2003 16:33:20 -0000 Received: from warrior.services.quay.plus.net (212.159.14.227) by mailstore with SMTP; 6 Mar 2003 16:33:20 -0000 Received: (qmail 25954 invoked from network); 6 Mar 2003 16:33:21 -0000 Received: from post.thorcom.com (193.82.116.70) by warrior.services.quay.plus.net with SMTP; 6 Mar 2003 16:33:21 -0000 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 4.12) id 18qyBx-000735-00 for rsgb_lf_group-outgoing@blacksheep.org; Thu, 06 Mar 2003 16:25:57 +0000 Received: from [62.253.162.43] (helo=mta03-svc.ntlworld.com) by post.thorcom.com with esmtp (Exim 4.12) id 18qyBs-00072w-00 for rsgb_lf_group@blacksheep.org; Thu, 06 Mar 2003 16:25:52 +0000 Received: from mike1 ([80.4.107.45]) by mta03-svc.ntlworld.com (InterMail vM.4.01.03.27 201-229-121-127-20010626) with ESMTP id <20030306162551.RWQ24607.mta03-svc.ntlworld.com@mike1> for ; Thu, 6 Mar 2003 16:25:51 +0000 Message-ID: <001001c2e3f5$d2ac6000$2602a8c0@WorkGroup> From: "mike.dennison" To: rsgb_lf_group@blacksheep.org References: Date: Thu, 6 Mar 2003 15:34:05 -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: LF broadband QRN? 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 > Since the 73kHz tests on Tuesday I have been monitoring at several times a > day and find a consistent and steady noise-level that is about 20dB below > the signal at 138.8kHz, and about 6dB below the one at 75kHz. Its a mains > type of buzz, beating at times with itself. Like most I have had this in > the past and put it down to RFI from switched-mode PSUs, however, it was > only sporadic in the past so I am wondering if it's something new. It seems > to be all the way up the LF band to just below the LW broadcast band (but > that cut-off could be a function of my aerial's resonance set at 73kHz). > > The only thoughts that I have is ADSL or signalling on the HV underground > cable somewhere beneath my garden. > > How far away do TV's etc need to be before they cause problems, or > is it more caused by the interference conducting itself along the mains > cabling, etc. > Any thoughts? > > 73 John, G3WKL I don't have ADSL, but I (and several of my neighbours) have cable modems supplied by NTL running between 128kb and 1Mb. My modem, and the unscreened switch/gateway for my small network are both in the shack and only a couple of metres from the antenna. I do not experience any problems to/from either on LF. My main noise sources are TVs, video recorders and computer games. These seem to be within a few metres of my house. I fixed the QRM from my own TV by using a braid breaker. I have found QRM radiated by power lines (and once a telephone line) whilst out portable, but have not located the source. Mike, G3XDV http://www.lf.thersgb.net ====================