Return-Path: Received: (qmail 17129 invoked from network); 29 Apr 2003 17:18:53 -0000 Received: from netmail01.services.quay.plus.net (212.159.14.219) by mailstore with SMTP; 29 Apr 2003 17:18:53 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: (qmail 22643 invoked by uid 10001); 29 Apr 2003 17:18:53 -0000 Received: from post.thorcom.com (193.82.116.70) by netmail01.services.quay.plus.net with SMTP; 29 Apr 2003 17:18:53 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 4.14) id 19AYkA-0007U4-Ep for rsgb_lf_group-outgoing@blacksheep.org; Tue, 29 Apr 2003 18:18:14 +0100 Received: from [204.60.203.69] (helo=mta3.snet.net) by post.thorcom.com with esmtp (Exim 4.14) id 19AYk4-0007Tr-S4 for rsgb_lf_group@blacksheep.org; Tue, 29 Apr 2003 18:18:09 +0100 Received: from snet.net (12-209-21-79.client.attbi.com [12.209.21.79]) (authenticated bits=0) by mta3.snet.net (8.12.3/8.12.3/SNET-smtp-1.2/D-1.1.1.1/O-1.1.1.1) with ESMTP id h3THI48F025526 for ; Tue, 29 Apr 2003 13:18:07 -0400 (EDT) Message-ID: <3EAEB497.1A5793CA@snet.net> Date: Tue, 29 Apr 2003 13:21:27 -0400 From: "Jay Rusgrove" X-Mailer: Mozilla 4.76 [en] (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <5.1.0.14.0.20030429145925.00ae4c60@gemini.herts.ac.uk> Subject: Re: LF: LF Tuning meter Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, hits=-22.8 required=5.0tests=EMAIL_ATTRIBUTION,QUOTED_EMAIL_TEXT,REFERENCES, REPLY_WITH_QUOTESversion=2.53 X-Spam-Checker-Version: SpamAssassin 2.53 (1.174.2.15-2003-03-30-exp) X-SA-Exim-Scanned: Yes Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rsgb_lf_group-outgoing@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false Jim I would also appreciate a copy of the .pdf. If someone has hosted it on their website a link would also be acceptable. I have used the scope version for some time now and it works quite well. Look forward to not having to drag the scope with me. Thanks for sharing the info. Jay Rusgrove, W1VD James Moritz wrote: > Dear LF Group, > > For tuning LF antennas, I have for some time been using an oscilloscope to > monitor the current and voltage waveforms at the TX output. Resonance > occurs when V and I are in phase, and the load resistance is 50ohms when > V/I = 50. This is very easy to use provided a scope is to hand, but not > very useful if it isn't. An SWR bridge can be used, but it only indicates > the degree of mismatch, so tuning is still a matter of trial and error. So > with a mind towards future /P operations, I have built a self-contained > tuning meter. > > The prototype has 2 meters - one indicates phase, while the other can be > switched between voltage and current to determine the load resistance. The > circuit is slightly more complex than an SWR bridge, but not by very much - > it uses 12 diodes, 3 toroid cores and a few other passive components. It > does not require an external power supply, and is usable with TX power > between about 20W and 1.8kW. I have written a 3 page article about it - it > is a pdf file of about 190k, so too big for the reflector, but I can e-mail > it as an attachment to those who are interested. If someone would like to > put it on their web site, they would be more than welcome! > > Cheers, Jim Moritz > 73 de M0BMU