Return-Path: Received: from mtain-de01.r1000.mx.aol.com (mtain-de01.r1000.mx.aol.com [172.29.64.201]) by air-mc02.mail.aol.com (v129.4) with ESMTP id MAILINMC024-a8d64d4c3eec399; Fri, 04 Feb 2011 13:01:16 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-de01.r1000.mx.aol.com (Internet Inbound) with ESMTP id DD5F2380000C2; Fri, 4 Feb 2011 13:01:14 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PlPwy-0005kr-Qq for rs_out_1@blacksheep.org; Fri, 04 Feb 2011 18:00:04 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PlPwy-0005ki-Eb for rsgb_lf_group@blacksheep.org; Fri, 04 Feb 2011 18:00:04 +0000 Received: from 113-mo2-8.acn.waw.pl ([62.121.95.113] helo=paranoid.lipkowski.org) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PlPww-0001Tb-NV for rsgb_lf_group@blacksheep.org; Fri, 04 Feb 2011 18:00:04 +0000 Received: from paranoid.lipkowski.org (localhost [127.0.0.1]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id p14I00Lp016390 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Fri, 4 Feb 2011 19:00:00 +0100 Received: from localhost (sq5bpf@localhost) by paranoid.lipkowski.org (8.13.7/8.13.6/Submit) with ESMTP id p14I00W7016387 for ; Fri, 4 Feb 2011 19:00:00 +0100 X-Authentication-Warning: paranoid.lipkowski.org: sq5bpf owned process doing -bs Date: Fri, 4 Feb 2011 19:00:00 +0100 (CET) From: Jacek Lipkowski To: rsgb_lf_group@blacksheep.org In-Reply-To: Message-ID: References: MIME-Version: 1.0 X-Spam-Score-sq5bpf: -2.601 () BAYES_00,SPF_HELO_PASS,SPF_PASS X-Scanned-By: MIMEDefang 2.56 on 10.1.3.10 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: Re: LF: Earth-mode or not earth-mode 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: 3039ac1d40c94d4c3eea3a85 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) On Thu, 3 Feb 2011, John Rabson wrote: > Some years ago, we tried using a small loop to couple a Heyphone (4 W > output on 87 kHz) into a running rail in a disused railway tunnel in the > English Midlands (we had permission from the owners of the line). A > similar setup was used for receive and we achieved a range of 1.6 km > along the line. 1.6km is a very good result, since a Heyphone is basically a lf ssb transceiver so you probably used voice, and the loop was probably unmatched. you would achieve much larger distances if you tried qrss with a better matched antenna. you can try this with overhead powerlines in rural areas too if you can fit your signal between the harmonics. long phone lines work well too. btw. i have tried running a few watts at 8.9kHz to a loop abt. 1.5x2.5m in the middle of the city (who knows what it's coupling to :). the signal can be received at over 600m distance with a small loop antenna near power lines, and is generally a nice indicator of underground conductive structures (this method is also used to find illegal tunels) jacek