Return-Path: Received: (qmail 18081 invoked from network); 15 Jul 2002 23:43:32 -0000 Received: from murphys.services.quay.plus.net (212.159.14.225) by mailstore with SMTP; 15 Jul 2002 23:43:32 -0000 Received: (qmail 28671 invoked from network); 15 Jul 2002 23:42:46 -0000 Received: from post.thorcom.com (193.82.116.70) by murphys.services.quay.plus.net with SMTP; 15 Jul 2002 23:42:46 -0000 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 3.33 #2) id 17UFP0-0000Ar-00 for rsgb_lf_group-outgoing@blacksheep.org; Tue, 16 Jul 2002 00:37:14 +0100 Received: from out4.mx.nwbl.wi.voyager.net ([169.207.3.122]) by post.thorcom.com with esmtp (Exim 3.33 #2) id 17UFOz-0000Am-00 for rsgb_lf_group@blacksheep.org; Tue, 16 Jul 2002 00:37:13 +0100 Received: from mail6.mx.voyager.net (mail6.mx.voyager.net [216.93.66.205]) by out4.mx.nwbl.wi.voyager.net (8.12.3/8.11.4/1.7) with ESMTP id g6FNbA1Y021231 for ; Mon, 15 Jul 2002 18:37:10 -0500 Received: from k6500 (d5.as3.mpls.mn.voyager.net [169.207.249.229] (may be forged)) by mail6.mx.voyager.net (8.11.6/8.10.2) with SMTP id g6FNb8K08271 for ; Mon, 15 Jul 2002 19:37:08 -0400 (EDT) From: "WE0H" To: rsgb_lf_group@blacksheep.org Subject: RE: LF: Ground loss/gain Date: Mon, 15 Jul 2002 18:37:33 -0500 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 8bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2911.0) In-reply-to: <5.1.0.14.0.20020715170020.02e95028@gemini.herts.ac.uk> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Importance: Normal Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: This makes sense since the loopers around the US have found out that the loop current is highest during the dry days. When it rains, the current goes down. 73's, Mike>WE0H http://www.we0h.us/lf.html -----Original Message----- From: majordom@post.thorcom.com [mailto:majordom@post.thorcom.com]On Behalf Of James Moritz Sent: Monday, July 15, 2002 11:31 AM To: rsgb_lf_group@blacksheep.org Subject: Re: LF: Ground loss/gain (was: polarization of small loops) Dear LF Group, The maths required to calculate the gain and Rrad of a loop over a ground plane looks much too difficult... so I cheated and used EZNEC instead to simulate a 10m square loop 1m above a ground plane - the gain is close to 4.77dBi ( ie. 3), instead of 1.77dBi for a loop in free space, so 3dB gain due to the ground plane, as one would intuitively expect. I also tried simulating it with "real" grounds, to find out what the effect would be on the radiation resistance. Unfortunately, it does not like doing this, giving an error message saying that the resistance is negative and the loop is too small. I increased the frequency to 1MHz, where the simulation ran OK. Comparing Rrad with perfect ground and free space gave a ratio of about 2:1 as expected. With "high accuracy" ground, either very low or very high ground conductivity gave lower loss resistance than intermediate values, which also seems reasonable - the loss reached a maximum somewhere around 100mS, so this suggests that, with actual grounds having lower conductivity than this, loops will work best with the lowest possible ground conductivity. However, one has to take all this with a pinch of salt because of the simulation errors produced if the frequency is reduced. Cheers, Jim Moritz 73 de M0BMU