Return-Path: Received: (qmail 85807 invoked from network); 16 Jan 2005 20:07:37 -0000 Received: from unknown (HELO ptb-spamcore02.plus.net) (192.168.71.3) by ptb-mailstore02.plus.net with SMTP; 16 Jan 2005 20:07:37 -0000 Received: from mailnull by ptb-spamcore02.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1CqGcd-000HTb-8y for dave@picks.force9.co.uk; Sun, 16 Jan 2005 20:03:43 +0000 Received: from [192.168.67.3] (helo=ptb-mxcore03.plus.net) by ptb-spamcore02.plus.net with esmtp (Exim 4.32; FreeBSD) id 1CqGcd-000HTY-1R for dave@picks.force9.co.uk; Sun, 16 Jan 2005 20:03:39 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore03.plus.net with esmtp (Exim) id 1CqGgP-000OMw-1R for dave@picks.force9.co.uk; Sun, 16 Jan 2005 20:07:33 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1CqGdr-0005Wp-5c for rs_out_1@blacksheep.org; Sun, 16 Jan 2005 20:04:55 +0000 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1CqGdq-0005Wg-LK for rsgb_lf_group@blacksheep.org; Sun, 16 Jan 2005 20:04:54 +0000 Received: from smarthost0.mail.uk.easynet.net ([212.135.6.10]) by relay.thorcom.net with esmtp (Exim 4.43) id 1CqGdo-0004uL-9u for rsgb_lf_group@blacksheep.org; Sun, 16 Jan 2005 20:04:54 +0000 Received: from tnt-1-248.easynet.co.uk ([195.40.206.248] helo=erica) by smarthost0.mail.uk.easynet.net with smtp (Exim 4.10) id 1CqGdb-000J7Y-00 for rsgb_lf_group@blacksheep.org; Sun, 16 Jan 2005 20:04:39 +0000 Message-ID: <000401c4fb13$98ef8180$f8ce28c3@erica> From: "g3ldo" To: rsgb_lf_group@blacksheep.org References: <41EA3B2E.152.BF48D9@localhost> Date: Sat, 15 Jan 2005 15:04:07 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.50.4522.1200 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4522.1200 X-SPF-Result: relay.thorcom.net: 212.135.6.10 is neither permitted nor denied by domain of ukonline.co.uk X-Spam-Score: 0.3 (/) X-Spam-Report: autolearn=no,DATE_IN_PAST_24_48=0.302 Subject: LF: SWR-off topic 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) I am currently updating some of the antenna material in the RSGB Radio Communications Handbook. I have a question about SWR meters. In my early days of amateur radio I didn't have an SWR meter. I obtained some idea of antenna/feeder mismatch by using a multiple of half wavelength of coax and measuring the antenna feed Z using the Pi output capacitor (suitably calibrated) of the transmitter. At about the same time I was a RADAR technition in the RAF. When a magnetron was replaced on 3cm equipment (H2S) the SWR had to be measured using SWR meter. This comprised a small red neon tube, the sides of which were calibrated, like a thermometer, in SWR. As the tube was moved in a slot along the waveguide the maximum and minimum voltage could be seen (VSWR). The coax SWR meter can only detect voltage, current and phase. If you replace the antenna with a 200ohm resistor it will register an SWR of 2:1 even though there is no transmission line. From this only conclusion I can come to is that the standard SWR meter measures voltage, current and phase from which SWR is implied. So of all the radial scaled parameters to be found on the cursor of a Smith Chart why did someone settle for SWR?. Was a true SWR meter used in the days when radio engineers started feeding transmitters via long lengths of open wire feeder and became the standard measurement of antenna/feeder mismatch? Regards, Peter, G3LDO e-mail Web