Return-Path: Received: (qmail 14085 invoked from network); 17 Jan 2005 21:30:03 -0000 Received: from unknown (HELO ptb-spamcore02.plus.net) (192.168.71.3) by ptb-mailstore01.plus.net with SMTP; 17 Jan 2005 21:30:03 -0000 Received: from mailnull by ptb-spamcore02.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1CqeO6-000G1y-Ju for dave@picks.force9.co.uk; Mon, 17 Jan 2005 21:26:19 +0000 Received: from [192.168.67.3] (helo=ptb-mxcore03.plus.net) by ptb-spamcore02.plus.net with esmtp (Exim 4.32; FreeBSD) id 1CqeO5-000G1d-Iq for dave@picks.force9.co.uk; Mon, 17 Jan 2005 21:26:13 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore03.plus.net with esmtp (Exim) id 1CqeRf-0001L2-UU for dave@picks.force9.co.uk; Mon, 17 Jan 2005 21:29:56 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1CqeRS-0005N9-EI for rs_out_1@blacksheep.org; Mon, 17 Jan 2005 21:29:42 +0000 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1CqeRP-0005Mw-Tp for rsgb_lf_group@blacksheep.org; Mon, 17 Jan 2005 21:29:39 +0000 Received: from smtp809.mail.ukl.yahoo.com ([217.12.12.199]) by relay.thorcom.net with smtp (Exim 4.43) id 1CqeRM-0003w9-GG for rsgb_lf_group@blacksheep.org; Mon, 17 Jan 2005 21:29:39 +0000 Received: from unknown (HELO Main) (Alan.Melia@81.131.67.5 with login) by smtp809.mail.ukl.yahoo.com with SMTP; 17 Jan 2005 21:29:19 -0000 Message-ID: <000001c4fcdb$9cb71ca0$6507a8c0@Main> From: "Alan Melia" To: rsgb_lf_group@blacksheep.org References: <000001c4fc9a$d337d030$e6a4c593@RD40002> Date: Mon, 17 Jan 2005 14:17:24 -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: 217.12.12.199 is neither permitted nor denied by domain of btinternet.com X-Spam-Score: 0.2 (/) X-Spam-Report: autolearn=no,DATE_IN_PAST_06_12=0.211 Subject: LF: Re: RE: Re: Re: 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=0.6 required=5.0 tests=DATE_IN_PAST_06_12 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) ----- Original Message ----- From: "james moritz" To: Sent: 17 January 2005 13:45 Subject: LF: RE: Re: Re: SWR-off topic There are a bewildering array of modifications to the Smith chart, including expanded regions of low or high SWR, an inverted form with unity SWR at the outer edge of the chart (very odd scales on that one!) and versions for negative resistance (apparently useful for tunnel diode designs). Ah Jim, you have to remember maybe before and certainly after 1940 the common line amplifier in telephone trunk networks was a "Negative Resistance amplifier" . These were certainly used a lot in by GPO Telephones the UK and almost certainly by the Bell System. This is even before tunnel diodes were discovered/invented in the later 1950s. . A lot of the technicians and engineers would have got their training as radio and radar mechs in the forces. Cheers de Alan G3NYK