Return-Path: Received: (qmail 75897 invoked from network); 18 Jul 2004 10:58:01 -0000 Received: from unknown (HELO ptb-spamcore02.plus.net) (192.168.71.3) by ptb-mailstore02.plus.net with SMTP; 18 Jul 2004 10:58:01 -0000 Received: from mailnull by ptb-spamcore02.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1Bm9Oa-000HzL-WD for dave@picks.force9.co.uk; Sun, 18 Jul 2004 11:59:53 +0100 Received: from [192.168.67.1] (helo=ptb-mxcore01.plus.net) by ptb-spamcore02.plus.net with esmtp (Exim 4.32; FreeBSD) id 1Bm9Oa-000Hz9-U7 for dave@picks.force9.co.uk; Sun, 18 Jul 2004 11:59:52 +0100 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (Exim 4.30; FreeBSD) id 1Bm9Mk-000B3S-I1 for dave@picks.force9.co.uk; Sun, 18 Jul 2004 10:57:58 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Bm9MB-0004ql-Di for rs_out_1@blacksheep.org; Sun, 18 Jul 2004 11:57:23 +0100 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Bm9MB-0004qc-1z for rsgb_lf_group@blacksheep.org; Sun, 18 Jul 2004 11:57:23 +0100 Received: from smtp802.mail.ukl.yahoo.com ([217.12.12.139]) by relay.thorcom.net with smtp (Exim 4.34) id 1Bm9M7-0001wU-GL for rsgb_lf_group@blacksheep.org; Sun, 18 Jul 2004 11:57:23 +0100 Received: from unknown (HELO rogersservices) (james.moritz@81.131.217.7 with login) by smtp802.mail.ukl.yahoo.com with SMTP; 18 Jul 2004 10:57:13 -0000 Message-ID: <003101c46cb5$3ae3bb20$07d98351@rogersservices> From: "James Moritz" To: rsgb_lf_group@blacksheep.org References: <40FA5020.30632.4B8897@localhost> Date: Sun, 18 Jul 2004 11:51:49 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2615.200 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2615.200 X-Spam-Score: 0.1 (/) X-Spam-Report: autolearn=no,RCVD_IN_SORBS=0.1 Subject: LF: Re: Feeding grounded tower on 136KHz Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com 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 X-Spam-Filtered: by PlusNet SpamCORE (v3.00) Dear Mike, LF group, I think the feed point impedance of the shunt-fed mast will be a fairly low inductance in series with a loss resistance of a few ohms due to the feed wire and mast - essentially similar to a loop antenna. It would require a series capacitor to get resonance, plus a step-down transformer to match the TX load impedance. The trouble is that the impedance transformation produced by the shunt feed will convert the tenths of an ohm radiation resistance into micro-ohms at the feed point, which will just be lost in the loss resistance of the feed components. Cheers, Jim Moritz 73 de M0BMU ----- Original Message ----- From: Mike Dennison To: Sent: Sunday, July 18, 2004 10:25 AM Subject: LF: Feeding grounded tower on 136KHz > There has been lots of comment on how difficult it would be > to shunt match a grounded tower, but no-one has > commented on how to resonate the antenna. It seems to > me that the matching is the easy bit. > > Mike, G3XDV > =========== > >