Return-Path: Received: (qmail 12 invoked from network); 16 Jul 2001 10:33:49 -0000 Received: from unknown (HELO warrior-inbound.servers.plus.net) (212.159.14.227) by excalibur.plus.net with SMTP; 16 Jul 2001 10:33:49 -0000 Received: (qmail 24290 invoked from network); 16 Jul 2001 10:32:26 -0000 Content-Transfer-Encoding: 8bit Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by warrior with SMTP; 16 Jul 2001 10:32:26 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: from majordom by post.thorcom.com with local (Exim 3.16 #2) id 15M5ZY-0003ol-00 for rsgb_lf_group-outgoing@blacksheep.org; Mon, 16 Jul 2001 11:25:52 +0100 Received: from mail.cc.kuleuven.ac.be ([134.58.10.6]) by post.thorcom.com with esmtp (Exim 3.16 #2) id 15M5ZV-0003og-00 for rsgb_lf_group@blacksheep.org; Mon, 16 Jul 2001 11:25:49 +0100 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from LCBD15.fys.kuleuven.ac.be (LCBD15.fys.kuleuven.ac.be [134.58.80.15]) by mail.cc.kuleuven.ac.be (8.9.3/8.9.0) with SMTP id MAA76736 for ; Mon, 16 Jul 2001 12:25:07 +0200 Message-ID: <3.0.1.16.20010716112456.2acf7454@mail.cc.kuleuven.ac.be> X-Sender: pb623250@mail.cc.kuleuven.ac.be X-Mailer: Windows Eudora Pro Version 3.0.1 (16) Date: Mon, 16 Jul 2001 11:24:56 To: rsgb_lf_group@blacksheep.org From: "Rik Strobbe" Subject: Re: LF: Near filed of 9kHz antenna III In-reply-to: <000b01c10c3d$d6f7ffc0$e22875d5@w8k3f0> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Hello Dick & group, >AO computes the feedpoint impedance as 0.042 - j16189 ohm. >Because efficiency is 26.4% the radiation resistance is 0.264 * 0.042 = 11 >milli-ohm. Using the simple formula for a short vertical : Rs = 40*(Pi*L/W)^2 where L = annena length and W = wavelength the radiation resistance for a 180m high vertical at 9kHz is 11.5 milliOhm And taking a antenna capacitance of 6pF/m the total capacitance is 1080pF or 16374 Ohm at 9kHz. So the simple formulas seem to work quite well, even at VLF. Another thing : I like Andy's idea about ground-loops. Maybe we can put out some signal without handing many 100kV. I believe that others have tested some kind of ground dipoles too (VK2ZTO ?). 73, Rik ON7YD