Return-Path: Received: (qmail 15134 invoked from network); 4 Apr 2003 22:13:54 -0000 Received: from netmail01.services.quay.plus.net (212.159.14.219) by mailstore with SMTP; 4 Apr 2003 22:13:54 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: (qmail 19910 invoked by uid 10001); 4 Apr 2003 22:13:54 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from post.thorcom.com (193.82.116.70) by netmail01.services.quay.plus.net with SMTP; 4 Apr 2003 22:13:54 -0000 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 4.14) id 191ZQY-0004CA-9Y for rsgb_lf_group-outgoing@blacksheep.org; Fri, 04 Apr 2003 23:12:50 +0100 Received: from [212.35.226.183] (helo=k2.pncl.co.uk) by post.thorcom.com with esmtp (Exim 4.14) id 191ZQT-0004C1-JR for rsgb_lf_group@blacksheep.org; Fri, 04 Apr 2003 23:12:45 +0100 Received: from k7t.pncl.co.uk (157.235.35.212.in-addr.arpa.ip-pool.cix.co.uk [212.35.235.157]) by k2.pncl.co.uk (8.12.3/8.12.3/Debian-5) with ESMTP id h34MChPN029007 for ; Fri, 4 Apr 2003 23:12:44 +0100 Message-ID: <5.1.0.14.2.20030404222503.009f79d0@mail.pncl.co.uk> X-Sender: blanch@mail.pncl.co.uk X-Mailer: QUALCOMM Windows Eudora Version 5.1 Date: Fri, 04 Apr 2003 23:12:26 +0100 To: rsgb_lf_group@blacksheep.org From: "Walter Blanchard" MIME-Version: 1.0 Subject: LF: TX coil screening Content-Type: multipart/mixed; boundary="------------000705050607010904010806" X-Spam-Status: No, hits=0.0 required=5.0tests=noneversion=2.51 X-Spam-Checker-Version: SpamAssassin 2.51 (1.174.2.5-2003-03-20-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 This is a multi-part message in MIME format. --------------000705050607010904010806 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit Only just saw the postings re Decca coil screening. My Decca pal tells me he lined Decca Tx coil huts with copper (thin - 20g) to maintain constant dielectric environment and constant phase. The whole operation of Decca depended on maintaining accurate phase. Note - NOT grounded. Unlined huts caused considerable losses and phase shifts when wet outside. Timber huts used in N. Canada not too bad in winter when dry but lossy in summer when wet. VE's take note. Absolutely essential that proper bonding maintained between sheets - solder not screws. Does NOT cause losses if not grounded. Unimportant for amateurs because phase shifts don't matter, although if out in the open a conductive box around coil could prevent nearby wet bushes catching fire. A point about corona. Electrical discharge off a point can exist without being visible. I referred some time ago to the "green" edition of Terman for coil data. This referred to the 1943 edition of Terman - the one before transistors got in. I gather that when medium-wave went commercial in the UK back in the 60's copies of this edition were fetching £100 a time. Walter G3JKV. --------------000705050607010904010806 Content-Type: text/plain; charset=windows-1252; name="ATT11769.txt" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="ATT11769.txt" --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.459 / Virus Database: 258 - Release Date: 25/02/03 --------------000705050607010904010806--