Return-Path: Received: (qmail 23024 invoked from network); 10 May 2001 16:40:55 -0000 Received: from unknown (HELO murphys-inbound.servers.plus.net) (212.159.14.225) by excalibur-qfe1-smtp-plusnet.harl.plus.net with SMTP; 10 May 2001 16:40:55 -0000 Received: (qmail 26499 invoked from network); 10 May 2001 14:16:04 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by murphys with SMTP; 10 May 2001 14:16:04 -0000 Content-Transfer-Encoding: 8bit Received: from majordom by post.thorcom.com with local (Exim 3.16 #2) id 14xr21-0007Yv-00 for rsgb_lf_group-outgoing@blacksheep.org; Thu, 10 May 2001 15:03:05 +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 14xr1x-0007Yq-00 for rsgb_lf_group@blacksheep.org; Thu, 10 May 2001 15:03:01 +0100 X-MSMail-Priority: Normal Received: by bob.dera.gov.uk; (8.8.8/1.3/10May95) id PAA27937; Thu, 10 May 2001 15:06:26 +0100 (BST) Received: (qmail 13754 invoked from network); 10 May 2001 14:54:23 -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; 10 May 2001 14:54:23 -0000 Received: by gauntlet.mail.dera.gov.uk; id OAA23294; Thu, 10 May 2001 14:49:46 GMT Received: from unknown(10.71.64.31) by gauntlet.mail.dera.gov.uk via smap (3.2) id xma023012; Thu, 10 May 01 14:48:55 GMT Received: from FRN-MAIL-3.dera.gov.uk (unverified) by mailguard.dera.gov.uk (Content Technologies SMTPRS 4.1.5) with ESMTP id for ; Thu, 10 May 2001 15:07:26 +0100 Received: by frn-mail-3.dera.gov.uk with Internet Mail Service (5.5.2650.21) id ; Thu, 10 May 2001 14:59:39 +0100 Message-ID: <65AECDF1F89AD411900400508BFC869F9C0496@pdw-mail-1.dera.gov.uk> From: "Talbot Andrew" To: rsgb_lf_group@blacksheep.org Subject: RE: LF: harmonics / LF antenna Date: Thu, 10 May 2001 14:59:51 +0100 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2650.21) 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: The local Non Directional Beacon here, EAS at Southampton Airport on 391.5kHz, puts out strong odd order harmonics. The fifth harmonic on 1957.5 actually caused QRM once. The third harmonic is masked by a local broadcast station at my QTH, but would probably be a problem to listeners nearer the airport. Does anyone know the internal design of these NDBs- wouldn't surprise me if they drive a squarewave to their (what looks to be rather small) antenna. In which case how do they generate the AM ? Wonder if I should complain to the RIS about the interference ? Might be worth taking a trip around the perimeter road with the car radio tuned to 1174 kHz, or better still, the local station on 1170kHz and hope it interferes. Andy G4JNT > > >So sending a few 100W square wave into a big antenna is not really > >recommended. -- 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.