Return-Path: Received: from mtain-dg09.r1000.mx.aol.com (mtain-dg09.r1000.mx.aol.com [172.29.65.17]) by air-da09.mail.aol.com (v129.4) with ESMTP id MAILINDA092-86194d07d6dea6; Tue, 14 Dec 2010 15:43:10 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dg09.r1000.mx.aol.com (Internet Inbound) with ESMTP id 9A1E0380000AD; Tue, 14 Dec 2010 15:43:08 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PSbhU-0004ne-1C for rs_out_1@blacksheep.org; Tue, 14 Dec 2010 20:42:20 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PSbhT-0004nV-J6 for rsgb_lf_group@blacksheep.org; Tue, 14 Dec 2010 20:42:19 +0000 Received: from imr-da05.mx.aol.com ([205.188.105.147]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PSbhR-0007A2-Nr for rsgb_lf_group@blacksheep.org; Tue, 14 Dec 2010 20:42:19 +0000 Received: from mtaout-ma02.r1000.mx.aol.com (mtaout-ma02.r1000.mx.aol.com [172.29.41.2]) by imr-da05.mx.aol.com (8.14.1/8.14.1) with ESMTP id oBEKfqVE000444 for ; Tue, 14 Dec 2010 15:41:55 -0500 Received: from White (nrbg-4d073628.pool.mediaWays.net [77.7.54.40]) by mtaout-ma02.r1000.mx.aol.com (MUA/Third Party Client Interface) with ESMTPA id 1ECA2E0007B7 for ; Tue, 14 Dec 2010 15:41:50 -0500 (EST) Message-ID: From: "Markus Vester" To: References: <007901cb9bbf$2c223810$0401a8c0@xphd97xgq27nyf>, Date: Tue, 14 Dec 2010 21:42:25 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 12.0.1606 X-MimeOLE: Produced By Microsoft MimeOLE V12.0.1606 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: BODGE ANTENNAS Content-Type: multipart/alternative; boundary="----=_NextPart_000_0014_01CB9BD7.CC492250" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.7 required=5.0 tests=HTML_40_50,HTML_FONTCOLOR_BLUE, HTML_MESSAGE,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-sid: 3039ac1d41114d07d6dc6f62 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none ------=_NextPart_000_0014_01CB9BD7.CC492250 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Yes Rik, theoretically the efficiency should be independent of soil re= sistivity: Loss resistance ~ resistivity, radiation resistance ~ area ^2 ~ skin depth ^2 ~ resistivity. In practice the situation may be different, because the loss resistanc= e occurs predominantly in the immediate vicinity of the earth contacts= . The return current depth depends more on the large-scale ground prop= erties, including deeper layers along the whole length of the antenna.= In the ELF facilities, deep well grounding was used to minimize local= current densities and potential gradients near the ends. Best 73, Markus (DF6NM) =20 From: Rik Strobbe=20 Sent: Tuesday, December 14, 2010 9:11 PM To: rsgb_lf_group@blacksheep.org=20 Subject: RE: LF: BODGE ANTENNAS In my view it does work as a loop antenna on 136 and 500kHz with the= loop area being determined by the soil conductivity (lower conductivi= ty, bigger loop area). The very fact that it is low-Q does suggest lo= ss.=20 Hello Roger, if=20 low conductivity =3D large loop area (A) but small antenna current (I) high conductivity =3D small loop area (A) but large antenna current (I= ) Would this result in A*I =3D constant ? The radiation resistance of a loop is proportional to the square or th= e loop area (A). And the ERP is proportional to the square of the ante= nna current (I).=20 If A*I is a constant (independent or soil conductivity) this would mea= n that the ERP would no depend on soil conductivity ? 73, Rik ON7YD - OR7T=20 ------=_NextPart_000_0014_01CB9BD7.CC492250 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Yes Rik, theoretically the efficiency= should be=20 independent of soil resistivity:
 
Loss resistance ~ resistivity,=
radiation resistance ~ area ^2 ~ skin= depth ^2 ~=20 resistivity.
<= FONT face=3DArial> 
In practice the situation may be different, be= cause the=20 loss resistance occurs predominantly in the immediate vicini= ty of the=20 earth contacts. The return current depth depends more on the= =20 large-scale ground properties, including deeper layers along= the whole=20 length of the antenna. In the ELF facilities, deep well grounding = ;was used=20 to minimize local current densities and potential gradients near the= =20 ends.
 
Best 73,
Markus (DF6NM)

 
Sent: Tuesday, December 14, 2010 9:11 PM
Subject: RE: LF: BODGE ANTENNAS
=
In my view it does work as a loo= p antenna on=20 136 and 500kHz with the loop area being determined by the soil conduct= ivity=20 (lower conductivity, bigger loop area).  The very fact that it is= low-Q=20 does suggest loss.
 
Hello Roger,
&nb= sp;
if 
low conductivity =3D large= loop=20 area (A) but small antenna current (I)
high conductivity =3D smal= l loop area (A)=20 but large antenna current (I)
Would this result in A*I= =3D constant=20 ?
 
The radiation resistance= of a loop is=20 proportional to the square or the loop area (A). And the ERP is propor= tional to=20 the square of the antenna current (I).
If A*I is a constant (inde= pendent or soil=20 conductivity) this would mean that the ERP would no depend on soil con= ductivity=20 ?
 
73, Rik  ON7YD -=20 OR7T 
 
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