Return-Path: Received: from rly-db09.mx.aol.com (rly-db09.mail.aol.com [172.19.130.84]) by air-db07.mail.aol.com (v123.4) with ESMTP id MAILINDB073-ae44a1c4f94375; Tue, 26 May 2009 16:23:00 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-db09.mx.aol.com (v123.4) with ESMTP id MAILRELAYINDB092-ae44a1c4f94375; Tue, 26 May 2009 16:22:47 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1M93A5-0006qx-J8 for rs_out_1@blacksheep.org; Tue, 26 May 2009 21:22:13 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1M93A5-0006qo-7t for rsgb_lf_group@blacksheep.org; Tue, 26 May 2009 21:22:13 +0100 Received: from smtp802.mail.ird.yahoo.com ([217.146.188.62]) by relay1.thorcom.net with smtp (Exim 4.63) (envelope-from ) id 1M93A2-0001E6-KX for rsgb_lf_group@blacksheep.org; Tue, 26 May 2009 21:22:12 +0100 Received: (qmail 53944 invoked from network); 26 May 2009 20:22:04 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=btopenworld.com; h=Received:X-YMail-OSG:X-Yahoo-Newman-Property:Message-ID:From:To:References:In-Reply-To:Subject:Date:MIME-Version:Content-Type:Content-Transfer-Encoding:X-Priority:X-MSMail-Priority:X-Mailer:X-MimeOLE; b=G7WyQtUh+SYG4XqguUi3lY8Bg69SGFtlr9y2VcvVIBfafXtNA4PKfLVPCEm+bKboMbRnUSMa2vM2kKpfbsQzpNqpX7ZWfMicYpiZ2qa+R9znFm+bR363bhHISbyYdlHIICmH/HThcNe+9XlqKNefkvCea7UFbzxFWeKnCjv72/s= ; Received: from unknown (HELO JimPC) (james.moritz@86.177.111.34 with login) by smtp802.mail.ird.yahoo.com with SMTP; 26 May 2009 20:22:04 -0000 X-YMail-OSG: SS235H8VM1miFD0Iw67gpvhoKTndumrIjFxvQ8dAF2p1eT8xO_NARwY2izeGgtig8ktP6kfU4dqcSa7mF.nNgh1r6HXkhn1dxtTs8UKMJ9irHFVi1wZen5kh7GWwrJl9JVmSJXjsjnV.47kSgFdfL9TtFe95kSjxe4EaSJZZcLlxAP6TEvb4cnjUODdt3cJTUN2FOWGZwZSSIbXo9qghP6eW X-Yahoo-Newman-Property: ymail-3 Message-ID: <40A8C7C3E5D74E4B9462C7F7FB696203@JimPC> From: "James Moritz" To: References: <4A199D1F.7070201@btconnect.com> In-Reply-To: <4A199D1F.7070201@btconnect.com> Date: Tue, 26 May 2009 21:22:03 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6001.18000 X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6001.18049 X-Karma: unknown: DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: LF: Re: Modelling aerials Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=response Content-Transfer-Encoding: 7bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.1 required=5.0 tests=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-IP: 193.82.116.20 Dear Richard, LF Group, > I am trying to model various aerial configurations for 500kHz using NEC. I > have set the antenna 0.5m above ground as NEC2 does not like radials on > the ground. I have used "real ground". Has anyone compared the calculated > Source impedances to real-world measurements at 500kHz? The conclusion I came to was that the elevated radials do not model the ground system very realistically. Also, the real antenna resistance can vary a lot with differnet kinds of environment. The disclaimer might go "any resemblance to real figures is purely coincidental"! NEC is a good way of working out the antenna capacitance and radiation resistance, though, using lossless wires and "perfect" ground. Cheers, Jim Moritz 73 de M0BMU