Return-Path: Received: from mtain-md04.r1000.mx.aol.com (mtain-md04.r1000.mx.aol.com [172.29.96.88]) by air-md07.mail.aol.com (v129.4) with ESMTP id MAILINMD071-8b8c4d44a9f8c; Sat, 29 Jan 2011 18:59:52 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-md04.r1000.mx.aol.com (Internet Inbound) with ESMTP id DADA138000095; Sat, 29 Jan 2011 18:59:50 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PjKh2-00084r-RG for rs_out_1@blacksheep.org; Sat, 29 Jan 2011 23:59:00 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PjKh2-00084i-EJ for rsgb_lf_group@blacksheep.org; Sat, 29 Jan 2011 23:59:00 +0000 Received: from mta11.charter.net ([216.33.127.80]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PjKgz-0003eR-VJ for rsgb_lf_group@blacksheep.org; Sat, 29 Jan 2011 23:59:00 +0000 Received: from imp10 ([10.20.200.15]) by mta11.charter.net (InterMail vM.7.09.02.04 201-2219-117-106-20090629) with ESMTP id <20110129235850.BPAN6966.mta11.charter.net@imp10> for ; Sat, 29 Jan 2011 18:58:50 -0500 Received: from [192.168.0.3] ([66.168.113.95]) by imp10 with smtp.charter.net id 1bym1g00423ZM9N05byqo5; Sat, 29 Jan 2011 18:58:50 -0500 X-Authority-Analysis: v=1.0 c=1 a=8nJEP1OIZ-IA:10 a=sScr6U9RAAAA:8 a=F3M5lZpKAAAA:8 a=oCcaPWc0AAAA:8 a=ephdZt4XgDP_iRV9ffgA:9 a=BC0tTgliZcLAxlhkVBgA:7 a=LNgUhdtn84QSWJhR9q8-jiB_4O8A:4 a=wPNLvfGTeEIA:10 a=uM05R_bXrMoA:10 a=wk6s2zzMB60A:10 Message-ID: <4D44ADB7.50108@charter.net> Date: Sat, 29 Jan 2011 19:15:51 -0500 From: John Andrews User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.13) Gecko/20101207 Thunderbird/3.1.7 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <4D449E50.2020507@o2.co.uk> <000c01cbc00e$4a122790$4001a8c0@lark> In-Reply-To: <000c01cbc00e$4a122790$4001a8c0@lark> X-Spam-Score: 1.4 (+) X-Spam-Report: autolearn=disabled,RATWARE_GECKO_BUILD=1.426 Subject: Re: LF: Re: LF coil tuning Content-Type: text/plain; charset=ISO-8859-1; format=flowed 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 x-aol-global-disposition: G x-aol-sid: 3039ac1d60584d44a9f61f8e X-AOL-IP: 195.171.43.25 X-Mailer: Unknown (No Version) Peter, It used to be common MW broadcast practice to use "eddy current disks", which were aluminum rings. In some cases, the ring was put inside the coil, with the ability to rotate it in and out of the plane of the turns. A simpler setup was to have it at one end, mounted on a threaded rod, allowing it to be moved along the axis of the coil. I'm sure there were consequences for "Q", but I don't recall any heating issues. John, W1TAG On 1/29/2011 6:43 PM, Alan Melia wrote: > Hi Peter I think this is analogous to putting an aluminium or brass slug > into a coil as with the VHF Toko range where there is an optional ferrite of > aluminium.core. I have never measured Qs I suspect it is a bit lossy maybe > that is why a single shorted turn is used for a loading coil. > > Alan > G3NYK > > ----- Original Message ----- > From: "Peter Dodd" > To: > Sent: Saturday, January 29, 2011 11:10 PM > Subject: LF: LF coil tuning > > >> 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 >> >> >> >> >> > > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.449 / Virus Database: 271.1.1/3411 - Release Date: 01/29/11 19:34:00 >