X-GM-THRID: 1239192540326630087 X-Gmail-Labels: rsgb lf Delivered-To: daveyxm@gmail.com Received: by 10.78.172.10 with SMTP id u10cs326459hue; Mon, 18 Jun 2007 16:43:21 -0700 (PDT) Received: by 10.82.174.20 with SMTP id w20mr12334509bue.1182210201169; Mon, 18 Jun 2007 16:43:21 -0700 (PDT) Return-Path: Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mx.google.com with ESMTP id 32si6326300nfu.2007.06.18.16.43.15; Mon, 18 Jun 2007 16:43:21 -0700 (PDT) Received-SPF: neutral (google.com: 193.82.116.20 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1I0Qp8-0006ZA-VY for rs_out_1@blacksheep.org; Tue, 19 Jun 2007 00:39:54 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1I0Qp8-0006Z1-Bs for rsgb_lf_group@blacksheep.org; Tue, 19 Jun 2007 00:39:54 +0100 Received: from pne-smtpout1-sn1.fre.skanova.net ([81.228.11.98]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1I0Qp7-0005Je-IV for rsgb_lf_group@blacksheep.org; Tue, 19 Jun 2007 00:39:54 +0100 Received: from [127.0.0.1] (62.20.250.132) by pne-smtpout1-sn1.fre.skanova.net (7.2.076.2) (authenticated as u33233109) id 46758F1900051415 for rsgb_lf_group@blacksheep.org; Tue, 19 Jun 2007 01:36:01 +0200 Message-ID: <467716E3.7070509@telia.com> Date: Tue, 19 Jun 2007 01:36:03 +0200 From: "Johan H. Bodin" User-Agent: Thunderbird 2.0.0.4 (Windows/20070604) MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <001f01c7ae26$3474ab40$c2137ad5@w4o8m9> <20070614125512.BD7D431E702@smtps01.kuleuven.be> <46718D94.8050303@telia.com> <20070615001329.6ikxlepiewskckg0@webmail3.kuleuven.be> In-Reply-To: <20070615001329.6ikxlepiewskckg0@webmail3.kuleuven.be> X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: Re: LF: M0BMU ERP on 500k Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: Quoted-Printable X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=none 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 Status: O X-Status: X-Keywords: X-UID: 1065 Rik Strobbe wrote: > Looking at the patterns: > am I right to conclude that not-so-perfect ground will only attenuate=20 > the surface wave (radiated at 0=B0) but will not affect skywave (or eve= n=20 > improve it a bit)? I don't know... But, experience from experiments, software simulations an= d reading a lot of books converge into the fact that vertical antennas over non-perfect ground do not radiate well at zero elevation. I believe it has something to do with the GND beeing a not-so-perfect mirror which, in addition to beeing lossy, also has some phase shift in its reflection coefficient. I guess... I think that most of this attenuation happens in the near field region which I believe is exactly what Jim M0BMU has found in his experiments; the FS falls off almost linearly with distance but it is a few dBs "too low". An FSM antenna at 2m height is below 1 degree elevation already at 114m distance from the TX (assuming that the Earth is flat, isn't it? ;-) ) 73 Johan SM6LKM