X-GM-THRID: 1208110107382287243 X-Gmail-Labels: rsgb lf X-Gmail-Received: 456b78812b9c6124a8240458275e7efec7a91e26 Delivered-To: daveyxm@gmail.com Received: by 10.64.249.17 with SMTP id w17cs142026qbh; Wed, 5 Jul 2006 16:53:00 -0700 (PDT) Received: by 10.48.218.19 with SMTP id q19mr43836nfg; Wed, 05 Jul 2006 16:53:00 -0700 (PDT) Return-Path: Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mx.gmail.com with ESMTP id c1si1987119nfe.2006.07.05.16.53.00; Wed, 05 Jul 2006 16:53:00 -0700 (PDT) Received-SPF: neutral (gmail.com: 193.82.116.20 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1FyH7J-0003bj-4T for rs_out_1@blacksheep.org; Thu, 06 Jul 2006 00:49:13 +0100 Received: from [193.82.59.130] (helo=relay2.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1FyH7I-0003ba-D3 for rsgb_lf_group@blacksheep.org; Thu, 06 Jul 2006 00:49:12 +0100 Received: from smtp814.mail.ukl.yahoo.com ([217.12.12.204]) by relay2.thorcom.net with smtp (Exim 4.51) id 1FyH7E-0002xe-HG for rsgb_lf_group@blacksheep.org; Thu, 06 Jul 2006 00:49:12 +0100 Received: (qmail 53167 invoked from network); 5 Jul 2006 23:49:03 -0000 Received: from unknown (HELO w4o8m9) (james.moritz@btopenworld.com@213.122.12.216 with login) by smtp814.mail.ukl.yahoo.com with SMTP; 5 Jul 2006 23:49:02 -0000 Received: from 127.0.0.1 (AVG SMTP 7.1.394 [268.9.9/382]); Thu, 06 Jul 2006 00:46:28 +0100 Message-ID: <003101c6a08d$3c0f33e0$d80c7ad5@w4o8m9> From: "James Moritz" To: References: <001101c69f68$fa306a90$6501a8c0@eagles> <001801c69f70$bef1a9a0$0300a8c0@lark> <000901c69f77$db074850$6501a8c0@eagles> <007501c6a05c$f69da600$3ece28c3@captbrian> <00a401c6a068$89d023c0$3ece28c3@captbrian> Date: Thu, 6 Jul 2006 00:46:28 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2615.200 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2615.200 X-Spam-Score: 0.5 (/) X-Spam-Report: autolearn=disabled,AWL=-2.125,RCVD_IN_NJABL_PROXY=1.026,RCVD_IN_SORBS_MISC=1.597 Subject: LF: Re: Antenna Tuning - variometers Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=none autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false Status: O X-Status: X-Keywords: X-UID: 4911 ----- Original Message ----- From: captbrian To: Sent: Wednesday, July 05, 2006 8:23 PM Subject: LF: Re: Re: Re: Re: Antenna Tuning > ongoing thought, If you use half the fixed coil and all of the varying coil > in series [ F/2 - V ] you should come near to zero inductance with coils > in opposition - certainly quite a low value. Dear Bryan, LF Group, For the variometer to go to zero, the mutual inductance has to cancel out the self inductance of the fixed and moveable coils when they are in the "opposing" position - in other words the magnetic fluxes generated by the two coils when they are carrying the same current have to cancel out perfectly, or they have to have a (negative) unity coupling coefficient. This can never be quite achieved in practice, k is always less than 1, but to get close you have to minimise the gap between the two coils. In the usual design of variometer, the moving inner coil has to be considerably smaller in diameter so that it can rotate to any angle inside the outer coil, and this restricts the tuning range due to the large gaps required. There are other geometrical forms of variometer that don't have this restriction, and have a larger range of variation, getting closer to L = 0. Cheers, Jim Moritz 73 de M0BMU