Return-Path: Received: from mtain-de01.r1000.mx.aol.com (mtain-de01.r1000.mx.aol.com [172.29.64.201]) by air-mc04.mail.aol.com (v129.4) with ESMTP id MAILINMC044-a9324bfbe6f0302; Tue, 25 May 2010 11:04:16 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-de01.r1000.mx.aol.com (Internet Inbound) with ESMTP id 9DB65380000A4; Tue, 25 May 2010 11:04:13 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1OGveN-0000oG-PO for rs_out_1@blacksheep.org; Tue, 25 May 2010 16:02:35 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1OGveN-0000o7-9d for rsgb_lf_group@blacksheep.org; Tue, 25 May 2010 16:02:35 +0100 Received: from smtp.qtxt.dns-iol.com ([195.200.78.13]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1OGveL-0004pB-I2 for rsgb_lf_group@blacksheep.org; Tue, 25 May 2010 16:02:35 +0100 Received: (qmail 27450 invoked by uid 507); 25 May 2010 17:02:04 +0200 Received: from unknown (HELO ?10.0.0.3?) (john.rabson@numeo.fr@217.67.155.178) by smtp.qtxt.dns-iol.com with SMTP; 25 May 2010 17:02:04 +0200 From: John Rabson Mime-Version: 1.0 (Apple Message framework v1078) Date: Tue, 25 May 2010 17:03:10 +0200 In-Reply-To: To: rsgb_lf_group@blacksheep.org References: <38A51B74B884D74083D7950AD0DD85E82A1C00@File-Server-HST.hst.e-technik.tu-darmstadt.de> <315092772.1763254.1274721526409.JavaMail.fmail@mwmweb035> , Message-Id: <08B3EB53-D26F-4C18-92AA-2555D3348039@numeo.fr> X-Mailer: Apple Mail (2.1078) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Content-Type: multipart/alternative; boundary=Apple-Mail-1-139846743 Subject: Re: LF: AW: 8.97kHz - Near field and radiated signals? X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,HTML_MESSAGE 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: 3039ac1d40c94bfbe6ed5440 X-AOL-IP: 193.82.116.20 --Apple-Mail-1-139846743 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii Rik, LF, On 25 May 2010, at 09:00CEST, Rik Strobbe wrote: "I am still wondering how= an earth current antenna really works. I have read an article that claime= d that such an antenna was an underground loop." Such antennas are very widely used for cave radio work. I understand they= approximate to a vertical loop, but the analysis of the propagation mecha= nism is not simple. =20 Some of the theory can be found in David Gibson's PhD thesis: "Channel Cha= racterisation and System Design for Sub-Surface Communications" (Leeds, 20= 04). Theory and practice have been discussed extensively in the Cave Radi= o & Electronics Group Journal. There is a bibliography of this which can= be searched at http://www.sat.dundee.ac.uk/bin/cregsearch 73 John F5VLF --Apple-Mail-1-139846743 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii I am still wondering how an earth current antenn= a really works. I have read an article that claimed that such an antenna= was an underground loop."

Such antennas= are very widely used for cave radio work.  I understand they approxi= mate to a vertical loop, but the analysis of the propagation mechanism is= not simple.  

Some of the theory can be fou= nd in David Gibson's PhD thesis: "Channel Characterisation and System Desi= gn for Sub-Surface Communications" (Leeds, 2004).  Theory and practic= e have been discussed extensively in the Cave Radio & Electronics Grou= p Journal.  There is a bibliography of this which can be searche= d at http://www.sat= .dundee.ac.uk/bin/cregsearch

73 John F5VLF

=3D --Apple-Mail-1-139846743--