Return-Path: Received: (qmail 25060 invoked from network); 19 Sep 2002 18:35:36 -0000 Received: from marstons.services.quay.plus.net (212.159.14.223) by mailstore with SMTP; 19 Sep 2002 18:35:36 -0000 Received: (qmail 4058 invoked by uid 10001); 19 Sep 2002 19:39:34 -0000 Received: from post.thorcom.com (193.82.116.70) by marstons.services.quay.plus.net with SMTP; 19 Sep 2002 19:39:34 -0000 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 4.10) id 17s68Y-0006jx-00 for rsgb_lf_group-outgoing@blacksheep.org; Thu, 19 Sep 2002 19:34:50 +0100 Received: from [212.135.6.14] (helo=smarthost4.mail.uk.easynet.net) by post.thorcom.com with esmtp (Exim 4.10) id 17s68Y-0006jn-00 for rsgb_lf_group@blacksheep.org; Thu, 19 Sep 2002 19:34:50 +0100 Received: from tnt-2-118.easynet.co.uk ([195.40.196.118] helo=erica) by smarthost4.mail.uk.easynet.net with smtp (Exim 3.35 #1) id 17s68X-0005yJ-00 for rsgb_lf_group@blacksheep.org; Thu, 19 Sep 2002 19:34:49 +0100 Message-ID: <000401c2600d$247cdf80$76c428c3@erica> From: "g3ldo" To: rsgb_lf_group@blacksheep.org References: <000e01c25ef4$877024e0$636868d5@oemcomputer> Date: Thu, 19 Sep 2002 19:47:43 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.50.4522.1200 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Subject: LF: Re: Capacity hat puzzle Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, hits=-0.1 required=5.0tests=FROM_NAME_NO_SPACESversion=2.31 Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Hi Mike > > Whilst the mast was down I modified the capacity hat. There are three 17m > long parallel wires, about 0.5 metres apart (total span 1m). The wires are > joined at both ends. (See http://www.lf.thersgb.net/antenna.htm for a > picture). > > I changed this so that the wires were only joined at the far end. Now the > vertical wire and the elevated coil are connected to the centre wire only. > The RF travels along this centre wire to the end, then back using the outer > two wires in parallel.. > > I expected this to increase the inductance of the antenna and so lower its > resonant frequency. The actual effect was the opposite - the frequency > increased and I had to add inductance at the base of the vertical. > I can't offer an explanation but modelled the two antenna configurations on EZNEC3. Making some assumptions regarding ground and the two coils the original configuration resonated at 336.7kHz. The new one resonated at 138kHz. There was also a 0.15dB loss with the latest configuration. Regards, Peter, G3LDO e-mail Web