Return-Path: Received: from mtain-de08.r1000.mx.aol.com (mtain-de08.r1000.mx.aol.com [172.29.64.208]) by air-mf04.mail.aol.com (v129.4) with ESMTP id MAILINMF044-8be84bd85c0c276; Wed, 28 Apr 2010 12:02:20 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-de08.r1000.mx.aol.com (Internet Inbound) with ESMTP id 9BD80380000C0; Wed, 28 Apr 2010 12:02:17 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1O79h0-0003ZQ-MN for rs_out_1@blacksheep.org; Wed, 28 Apr 2010 17:00:54 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1O79h0-0003ZH-AA for rsgb_lf_group@blacksheep.org; Wed, 28 Apr 2010 17:00:54 +0100 Received: from moutng.kundenserver.de ([212.227.126.186]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1O79gy-0005Lu-Bb for rsgb_lf_group@blacksheep.org; Wed, 28 Apr 2010 17:00:54 +0100 Received: from [192.168.1.64] (188-221-89-85.zone12.bethere.co.uk [188.221.89.85]) by mrelayeu.kundenserver.de (node=mrbap2) with ESMTP (Nemesis) id 0M03PY-1NFK540kbU-00ufBC; Wed, 28 Apr 2010 18:00:46 +0200 From: "Dave Sergeant" To: rsgb_lf_group@blacksheep.org Date: Wed, 28 Apr 2010 17:00:45 +0100 MIME-Version: 1.0 Message-ID: <4BD85BAD.18368.2436C56@dave.davesergeant.com> In-reply-to: References: <003201cae3db$b7ffad50$0301a8c0@your91hoehfy9g>, <006e01cae6e3$2d46f4b0$4001a8c0@lark>, X-mailer: Pegasus Mail for Windows (4.52) Content-description: Mail message body X-Provags-ID: V01U2FsdGVkX1+ase5K5ZBmGd2c3VuMpnp8lpHC/3CYi04v4uS atrHFZYa+V2/Jay4APuNJbE1Vf95WeL7SKN95+ii3SOG+IgI9k qlkZZCs/9tCGLnipEvYnmgaUvxFJWgI X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: LF: Re: W1VLF 8.97 KHz UPDATE Trees, Questions, Ground Content-type: text/plain; charset=US-ASCII 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: 3039ac1d40d04bd85c097409 X-AOL-IP: 193.82.116.20 On 28 Apr 2010 at 17:27, Rik Strobbe wrote: > Hi Alan, > > indeed, "low voltage" loops suffer far less from these losses. > But the radiation resistance of a loop falls with the 4th power of the > wavelength, whereas for a vertical it is only with the 2nd power. At > 9kHz a loop of 15m high and 40m long will have a radiation resistance of > merely 10 nanoOhm (on 137kHz it is 0.5 milliOhm). So get out 1mW on 9kHz > one would need to pump 330A into the antenna. Using 1cm diameter solid > copper wire for the loop (anything less will probably act as a fuse) the > loss resistance is at least 0.025 Ohm (just copper loss, no stray > currents etc) and 2.5kW will be needed. > > 73, Rik ON7YD Indeed. With all the problems I had with a small loop on 136kHz and the high circulating currents (20A ish at a few watts) I would imagine on at a 1/18th of the frequency would have an efficiency not far above zero.... 73 Dave G3YMC http://www.davesergeant.com