Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dd03.r1000.mx.aol.com (Internet Inbound) with ESMTP id 1D3E73800008B; Wed, 11 Jan 2012 15:45:47 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Rl52d-0004Z9-38 for rs_out_1@blacksheep.org; Wed, 11 Jan 2012 20:45:03 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Rl52c-0004Z0-Io for rsgb_lf_group@blacksheep.org; Wed, 11 Jan 2012 20:45:02 +0000 Received: from smtpout2.wanadoo.co.uk ([80.12.242.42] helo=smtpout.wanadoo.co.uk) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Rl52a-0003uo-8o for rsgb_lf_group@blacksheep.org; Wed, 11 Jan 2012 20:45:02 +0000 Received: from computereebf79 ([95.144.116.67]) by mwinf5d30 with ME id LLkt1i00S1TKQcn03LktG5; Wed, 11 Jan 2012 21:44:54 +0100 Message-ID: <593F4C0651144C339855AFC49ED4329E@computereebf79> From: "Martin Evans" To: Date: Wed, 11 Jan 2012 20:44:50 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5931 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 X-Spam-Score: 3.4 (+++) X-Spam-Report: autolearn=disabled,FORGED_MUA_OUTLOOK=3.36 Subject: LF: Tuning inductance for 137kHz receive. Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original 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=1.6 required=5.0 tests=FORGED_MUA_OUTLOOK 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-SCOLL-SCORE: 0:2:400681152:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d408f4f0df4fb0d5d X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none I use a decade inductance bridge to series tune my (approximately) 50m end-fed inverted U wire for 137kHz. It uses 3mH - 2mH is too little, 4mH is too much. Obviously I need to be able to vary this inductance rather more finely and I thought of using a small variac (don't laugh!) as a variable inductance, connecting one end, and the tap, in series with the wire. Anyone know what the "inductance per turn", or total inductance, of such an animal might be? Any idea if it would work? Yes, I know I should wind a coil & tap it, but I like to be different! Martin GW3UCJ Swansea, South Wales.