Return-Path: Received: from mtain-md01.r1000.mx.aol.com (mtain-md01.r1000.mx.aol.com [172.29.96.85]) by air-db06.mail.aol.com (v129.4) with ESMTP id MAILINDB064-869a4d44b14d2b8; Sat, 29 Jan 2011 19:31:10 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-md01.r1000.mx.aol.com (Internet Inbound) with ESMTP id A218038000089; Sat, 29 Jan 2011 19:31:08 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PjLBQ-00005g-1P for rs_out_1@blacksheep.org; Sun, 30 Jan 2011 00:30:24 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PjLBP-00005X-Kr for rsgb_lf_group@blacksheep.org; Sun, 30 Jan 2011 00:30:23 +0000 Received: from n2b.bullet.mail.aue.yahoo.com ([124.108.96.191]) by relay1.thorcom.net with smtp (Exim 4.63) (envelope-from ) id 1PjLBN-0003rT-MW for rsgb_lf_group@blacksheep.org; Sun, 30 Jan 2011 00:30:23 +0000 Received: from [124.108.96.171] by n2.bullet.mail.aue.yahoo.com with NNFMP; 30 Jan 2011 00:30:12 -0000 Received: from [124.108.96.187] by t2.bullet.mail.aue.yahoo.com with NNFMP; 30 Jan 2011 00:30:12 -0000 Received: from [127.0.0.1] by omp102.mail.aue.yahoo.com with NNFMP; 30 Jan 2011 00:30:12 -0000 X-Yahoo-Newman-Id: 308017.28844.bm@omp102.mail.aue.yahoo.com Received: (qmail 41455 invoked by uid 1000); 30 Jan 2011 00:30:12 -0000 Received: from 124.108.96.74 by rel105.mail.aue.yahoo.com with SMTP; Sat, 29 Jan 2011 16:30:12 -0800 Received: (qmail 74341 invoked from network); 30 Jan 2011 00:30:11 -0000 Received: from sooby.xtra.co.nz (bjhayes@122.61.105.121 with login) by smtp105.tnz.mail.aue.yahoo.com with SMTP; 30 Jan 2011 11:30:11 +1100 EST X-Yahoo-SMTP: m6thF6mswBAnWxmjtcdhrNlLbX7_ea0yMMGOjaOYSQ-- X-YMail-OSG: LSzpjE8VM1ljDanA8wL6FYF6ufuPN0sM4AeY4gM2D5Yt78W EQM.0CJ1vo.Uu5ld8MPHwamHv3cDB6UzXi.YmNQHZ3Yu616u1yG8MDmj6B9L c0r2NFoD4MKPyVvElQQ_EdWPf.BeDzpCM2XPKE.E3gyC4QYp4CJk1lq0.hM6 x5Xk0dk.kDNossCzsQX9wBOLG_fTvRWQSdMoq8wqr2adoRCYQJzpeqHs1Ks1 FeubAZkk2ZL4.GqfzjO7pALeXsN0ALMiRrLhwn9RhnseejhTOwvs8zkL2 X-Yahoo-Newman-Property: ymail-3 Message-Id: <7.0.1.0.1.20110130125529.01b53f00@xtra.co.nz> X-Mailer: QUALCOMM Windows Eudora Version 7.0.1.0 Date: Sun, 30 Jan 2011 13:26:48 +1300 To: rsgb_lf_group@blacksheep.org From: Brenda Hayes In-Reply-To: <4D449E50.2020507@o2.co.uk> References: <4D449E50.2020507@o2.co.uk> Mime-Version: 1.0 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,UNPARSEABLE_RELAY=0.001 Subject: Re: LF: LF coil tuning Content-Type: text/plain; charset="us-ascii"; format=flowed 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 x-aol-global-disposition: G x-aol-sid: 3039ac1d60554d44b14c3ffe X-AOL-IP: 195.171.43.25 At 12:10 p.m. 30/01/2011, you wrote: >The traditional method of tuning an LF loading coil is to use a variometer. > >I have been investigating methods of tuning coils for mobile use and >one method that appeared briefly in one of the ARRL Handbooks of >the 50s was the shorted turn method of tuning. > >I tried a home made coil of 136uH on a 5cm diameter former and using >a shorted turn of 2mm insulated wire and obtained a tuning range of >32uH. (136 - 102uH). > >Has anyone out there tried this? > >Regards > >Peter G3LDO Hello Peter and the LF fraternity, I use a large ex-NDB loading coil that can be tapped on any single turn. For fine tuning there is a single rotary shorted turn.To minimise losses the cross-section of the shorted turn is large [about 40mm X 10mm] and the whole thing is silver-plated on brass. Although I have never bothered to measure the inductance variation it works well for transmitting on 180 and 500 kHz. I intend to try it on 136 kHz over our coming southern hemisphere winter. Cheers, Kevin ZL4MD