Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dh04.r1000.mx.aol.com (Internet Inbound) with ESMTP id 9354138000089; Tue, 31 Jan 2012 18:36:51 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1RsNEe-0005DL-O6 for rs_out_1@blacksheep.org; Tue, 31 Jan 2012 23:35:36 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1RsNEe-0005DC-6o for rsgb_lf_group@blacksheep.org; Tue, 31 Jan 2012 23:35:36 +0000 Received: from nm2.bt.bullet.mail.ird.yahoo.com ([212.82.108.233]) by relay1.thorcom.net with smtp (Exim 4.63) (envelope-from ) id 1RsNEd-0004gT-MP for rsgb_lf_group@blacksheep.org; Tue, 31 Jan 2012 23:35:36 +0000 Received: from [212.82.108.231] by nm2.bt.bullet.mail.ird.yahoo.com with NNFMP; 31 Jan 2012 23:35:29 -0000 Received: from [212.82.108.224] by tm4.bt.bullet.mail.ird.yahoo.com with NNFMP; 31 Jan 2012 23:35:29 -0000 Received: from [127.0.0.1] by omp1001.bt.mail.ird.yahoo.com with NNFMP; 31 Jan 2012 23:35:29 -0000 X-Yahoo-Newman-Id: 730201.44519.bm@omp1001.bt.mail.ird.yahoo.com Received: (qmail 85651 invoked from network); 31 Jan 2012 23:35:29 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=btopenworld.com; h=DKIM-Signature:X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Received:Message-ID:From:To:References:In-Reply-To:Subject:Date:MIME-Version:Content-Type:Content-Transfer-Encoding:X-Priority:X-MSMail-Priority:X-Mailer:X-MIMEOLE; b=d6Vy5YAft5wfmgPliLzfvS3F3oEv8SY8SDAbgv8/2LO/AB9bFnLoqWL65SAm45wNIQTtpOmPwjenRpGgL1HgpjzYpWvSJtTifQNgqmUtqZJinSm4P3eXGm50/OcBlpbGOUwQq/2z8IrH0YWA0BhnH03XQeWrbFEpeC8EjhrkcWM= ; DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=btopenworld.com; s=s1024; t=1328052929; bh=X7HJ1TWlxi2k6Wa//DdMTFnxSkSFtoye6GYLdDKlNbY=; h=X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Received:Message-ID:From:To:References:In-Reply-To:Subject:Date:MIME-Version:Content-Type:Content-Transfer-Encoding:X-Priority:X-MSMail-Priority:X-Mailer:X-MIMEOLE; b=BM/ZPHVfFpCcfqe4b5BukGJarPwkvkIkve8mhtZqSTOiWI4wWrEsmVr1r34Fti9LajoGw+Nchfp68k9pz5LC6To8IN+yKy5CgUwu5Rg7xpiZclfFh0c+ipphx5nbqtJr7O0BS0irNOoUaqCdf5gskUvLvnsJxpfKu4X8eWywczc= X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: 4sCxbO4VM1nQIK1Yah9825fAA_d1qs6jcQjjLGbK0SOaEbo bnKlHuFtw2qX575F1WbInxuqYEEzHSRsL3F14j5EivbtypP4.Twn6sDpsdJM UBw4A1nJOUHrzXE.slOpWLHA2eMWUvuphs4xB5HY1BTk6zXQgJvJbCH84bgo GXjzBdmcFbobyIej_gBDrjw6JP7iLQDEjkGKZ62EwvGbm1jcHhKu74KViLCw csG1d.naQ2JuDLIemGrKUCwC9.wmIos1HaCeUlQ8ppw67k22GFQTDt0hHsjI 6xM6pjLHhQ96eUOcp51j8.X0mULBysHg2pU8nfw2bXhdBppzA48qq0Gay6rQ fvlYpm0I2ll0RDMbM_bnZ5jVqoMe9gnlZVB9Hwxd2unhpzVDs1t8bKoUCa_d ZzVC.yUU0Nkhf40rHyWGERGV7Alc6vA-- X-Yahoo-SMTP: Cxhli3eswBD1ozmtAojhjrja86kWx0Qm9tycD5QR1DKWrOLgjJcXkw-- Received: from JimPC (james.moritz@86.161.95.2 with login) by smtp820.mail.ird.yahoo.com with SMTP; 31 Jan 2012 23:35:29 +0000 GMT Message-ID: From: "James Moritz" To: References: <4F286089.000027.05504@BOB-PC> In-Reply-To: <4F286089.000027.05504@BOB-PC> Date: Tue, 31 Jan 2012 23:35:33 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6002.18197 X-MIMEOLE: Produced By Microsoft MimeOLE V6.0.6002.18463 DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,UNPARSEABLE_RELAY=0.001 Subject: LF: Re: Converting antenna 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=0.1 required=5.0 tests=MISSING_OUTLOOK_NAME 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: 0:2:459239232:93952408 X-AOL-SCOLL-URL_COUNT: 0 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-d277.1 ; domain : btopenworld.com DKIM : fail x-aol-sid: 3039ac1d41184f287b1327f3 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none Dear Bob, LF Group, I guess as far as LF frequencies are concerned, the Butternut antenna is just a 10m vertical whip (provided you disconnect the coil across the feed point - otherwise it will be nearly a short circuited whip...). This will give you plenty of signal, provided the antenna is reasonably matched to the RX input. Matching requires tuning it to resonance. The simplest form of tuner is just an inductor connected between the feed point of the antenna and the low impedance RX input. The inductance needs to resonate with the antenna capacitance at 136kHz. A 10m vertical piece of tubing probably has about 100pF or so of capacitance, so quite a large inductance is needed, roughly 13mH. For receiving, small ferrite-cored chokes are OK as loading inductors - probably the easiest way to get this much inductance to to would be to get a small selection of 1mH and 2.2mH chokes and connect them in series - this makes it easy to adjust the inductance. This sort of arrangement gives a very sharp resonance, with a bandwidth of only 1kHz or so. For fine tuning, you can connect a variable capacitor say 100pF or so between the antenna and ground - this will reduce the available signal level a bit, and the required inductance, but is desirable due to the critical tuning. The signal level from an antenna this size should be enough for reasonably sensitive receivers - as you tune the antenna to resonance, you will hear a dramatic increase in signal levels and band noise. However, some receivers have very poor sensitivity at LF, so a preamp is sometimes needed. Hope this is helpful - good luck with LF! Cheers, Jim Moritz 73 de M0BMU