Return-Path: Received: from mtain-dg08.r1000.mx.aol.com (mtain-dg08.r1000.mx.aol.com [172.29.65.16]) by air-mf03.mail.aol.com (v129.4) with ESMTP id MAILINMF031-8bd94d07d4e5216; Tue, 14 Dec 2010 15:34:45 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dg08.r1000.mx.aol.com (Internet Inbound) with ESMTP id 1D6DE380001A2; Tue, 14 Dec 2010 15:34:43 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PSbZE-0004hB-K6 for rs_out_1@blacksheep.org; Tue, 14 Dec 2010 20:33:48 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PSbZE-0004h2-4s for rsgb_lf_group@blacksheep.org; Tue, 14 Dec 2010 20:33:48 +0000 Received: from out1.ip06ir2.opaltelecom.net ([62.24.128.242]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PSbZC-00076H-41 for rsgb_lf_group@blacksheep.org; Tue, 14 Dec 2010 20:33:48 +0000 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AgMFAIdjB01Z8n6//2dsb2JhbACRYpIxeMJRhUoEgWCMSw X-IronPort-AV: E=Sophos;i="4.59,344,1288569600"; d="scan'208,217";a="482781135" Received: from unknown (HELO xphd97xgq27nyf) ([89.242.126.191]) by out1.ip06ir2.opaltelecom.net with SMTP; 14 Dec 2010 20:33:40 +0000 Message-ID: <00ad01cb9bce$2dff85c0$0401a8c0@xphd97xgq27nyf> From: "mal hamilton" To: References: <007901cb9bbf$2c223810$0401a8c0@xphd97xgq27nyf> <7D6F2B55-E6E5-40BC-A7CF-D910C2232C9B@numeo.fr> Date: Tue, 14 Dec 2010 20:33:34 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: AOG antennas (was Re: LF: BODGE ANTENNAS) Content-Type: multipart/alternative; boundary="----=_NextPart_000_00AA_01CB9BCE.2DAE5880" 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: 3039ac1d41104d07d4e17d27 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : temperror ------=_NextPart_000_00AA_01CB9BCE.2DAE5880 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable John For your specific application short range Underground to Above ground= that seems the ideal environment for Earth mode induction/propagation= methods. however others are distorting the facts by claiming to be using earth= mode antennas when in fact they are using grounded loops and lossy di= poles by their own admission. also other factors distort the facts like enhanced propagation along a sewe= r pipe route, gas mains, water mains pipes and ancient burial grounds,= bone density etc To avoid any ambiguity I use the traditional methods like the commerci= al operators and use an elevated antenna as high in the air as possibl= e and insulated radials for the ground plane and avoid lossy buried gr= ound wires.=20 Some years ago the buried wire earth systems were replaced by elevated= radials on ground aeronautical DF and ground/air MF/HF installitions. de g3kev ----- Original Message -----=20 From: John Rabson=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Tuesday, December 14, 2010 7:49 PM Subject: AOG antennas (was Re: LF: BODGE ANTENNAS) On 14 Dec 2010, at 20:10CET, Roger Lapthorn wrote: Mal, Please, I make no magical claims for the earth electrode antenna= I use. All I say is that, in certain circumstances, it works rather= better than one might expect both on RX and TX on VLF/LF/MF. For cave-to-surface communications we have found that, in general,= an earth electrode system is much better than a tuned loop. When we= tried both systems at Kingsdale Master Cave Valley Entrance (a stand= ard CREG test site) the earth current antenna gave a 32 dB greater sig= nal at the surface than did the loop. It all seems to depend on the geology. If the top layer of the over= burden is essentially organic, then the loop tends to give better resu= lts. We still do not have a theoretical explanation for all this, but it= works. John F5VLF ------=_NextPart_000_00AA_01CB9BCE.2DAE5880 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
John
For your specific application short= range=20 Underground to Above ground that seems the ideal environment for Earth= mode=20 induction/propagation methods.
however others are distorting the fac= ts by claiming=20 to be using earth mode antennas when in fact they are using grounded= loops and=20 lossy dipoles by their own admission.
also
other factors distort the facts like= enhanced=20 propagation along a sewer pipe route, gas mains, water mains pipes and= ancient=20 burial grounds, bone density etc
To avoid any ambiguity I use the trad= itional=20 methods like the commercial operators and use an elevated antenna as= high in the=20 air as possible and insulated radials for the ground plane and avoid= lossy=20 buried ground wires.
Some years ago the buried= wire earth=20 systems were replaced by elevated radials on ground aeronautical= DF=20 and ground/air MF/HF installitions.
de g3kev
 
----- Original Message -----
From:=20 John=20 Rabson
Sent: Tuesday, December 14,= 2010 7:49=20 PM
Subject: AOG antennas (was Re= : LF: BODGE=20 ANTENNAS)

On 14 Dec 2010, at 20:10CET, Roger Lapthorn wrote:

Mal,

Please, I make no magic= al claims=20 for the earth electrode antenna I use. All I say is that, in certa= in=20 circumstances, it works rather better than one might expect both= on RX and=20 TX on VLF/LF/MF.

For cave-to-surface communica= tions we=20 have found that, in general, an earth electrode system is much bette= r than a=20 tuned loop.   When we tried both systems at Kingsdale Master Ca= ve=20  Valley Entrance (a standard CREG test site) the earth current= antenna=20 gave a 32 dB greater signal at the surface than did the loop.

It all seems to depend on the geology.  If the top layer= of the=20 overburden is essentially organic, then the loop tends to give bette= r=20 results.

We still do not have a theoretical explanation for all this, bu= t it=20 works.

John F5VLF

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