Return-Path: Received: (qmail 28021 invoked from network); 12 Jul 2002 15:13:33 -0000 Content-Transfer-Encoding: 8bit Received: from marstons.services.quay.plus.net (212.159.14.223) by mailstore with SMTP; 12 Jul 2002 15:13:33 -0000 X-MSMail-Priority: Normal Received: (qmail 4936 invoked by uid 10001); 12 Jul 2002 15:17:16 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from post.thorcom.com (193.82.116.70) by marstons.services.quay.plus.net with SMTP; 12 Jul 2002 15:17:16 -0000 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 3.33 #2) id 17T20V-00008f-00 for rsgb_lf_group-outgoing@blacksheep.org; Fri, 12 Jul 2002 16:06:55 +0100 Received: from tlvsca.vim.tlt.alcatel.it ([194.243.74.245]) by post.thorcom.com with esmtp (Exim 3.33 #2) id 17T20U-00008R-00 for rsgb_lf_group@blacksheep.org; Fri, 12 Jul 2002 16:06:54 +0100 Received: from tlvk7v (localhost [127.0.0.1]) by tlvsca.vim.tlt.alcatel.it (8.12.5/8.12.5) with SMTP id g6CF3K5N003070 for ; Fri, 12 Jul 2002 17:03:21 +0200 (MET DST) Date: Fri, 12 Jul 2002 13:36:12 +0100 From: "Claudio Girardi" Subject: LF: Ground loss/gain (was: polarization of small loops) To: rsgb_lf_group@blacksheep.org X-Mailer: Z-Mail Pro 6.2, NetManage Inc. [ZM62_16H] X-Priority: 3 Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=ISO-8859-1; format=flowed Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Hello all, I think that the "ground gain" and the "ground losses" depends on two different phenomena. Ground gain should come from reflections from ground at a distant point (far field) from the source combining with the direct ray from the same source with the proper phase. The type of antenna used shouldn't matter since it will be seen as a point source at a large distance; of course the polarization w.r.t. ground will be important. The ground losses depend on the presence of dissipative materials near the antenna (near field); for a small electric dipole the electric field near the antenna should be more intense than for a small magnetic loop. On the other hand, the magnetic field near a loop antenna should be higher than for an dipole. At a distance (far field) there is no difference between the two (for the same radiated power, of course). So probably for a monopole it is important to have a dielectric with low losses (and ground usually is not), while for a loop a lossy dielectric near the antenna has less effect, due to the weaker electric field. But I have no idea how lossy is the ground as a magnetic material... 73 de Claudio, IN3OTD Rik wrote: >And to make things more complex, what about a loop close to a >not-so-perfect ground plane ? >Either the loop is not (or little affected) by the ground. That means >little or no groundloss (as is claimed by some) but at the same time it >would mean that the loop will also not benefit from any "ground gain". >On the other hand, if the loop benifits form significantly from >"groundgain" then I would expect that the loop would also suffer from the >groundlosses, as a vertical monopole does. > >Any clues ?