Return-Path: Received: (qmail 11112 invoked from network); 27 May 2003 11:57:26 -0000 Received: from marstons.services.quay.plus.net (212.159.14.223) by mailstore with SMTP; 27 May 2003 11:57:26 -0000 Received: (qmail 635 invoked by uid 10001); 27 May 2003 11:57:25 -0000 Received: from post.thorcom.com (193.82.116.70) by marstons.services.quay.plus.net with SMTP; 27 May 2003 11:57:25 -0000 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 4.14) id 19Kd4J-0003u1-AN for rsgb_lf_group-outgoing@blacksheep.org; Tue, 27 May 2003 12:56:39 +0100 Received: from [62.253.162.42] (helo=mta02-svc.ntlworld.com) by post.thorcom.com with esmtp (Exim 4.14) id 19Kd4E-0003tq-1g for rsgb_lf_group@blacksheep.org; Tue, 27 May 2003 12:56:34 +0100 Received: from mike1 ([80.4.107.45]) by mta02-svc.ntlworld.com (InterMail vM.4.01.03.37 201-229-121-137-20020806) with SMTP id <20030527115631.KJYZ9882.mta02-svc.ntlworld.com@mike1> for ; Tue, 27 May 2003 12:56:31 +0100 Message-ID: <003c01c32447$217b1be0$2602a8c0@WorkGroup> From: "Mike Dennison" To: rsgb_lf_group@blacksheep.org References: Date: Tue, 27 May 2003 12:57:18 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.50.4133.2400 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Subject: LF: Re: Top loading - to short or not to short? Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, hits=-9.8 required=5.0tests=QUOTED_EMAIL_TEXT,REFERENCESversion=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 From: "Laurence J Howell > In looking at my LF Inverted L, and specifically the 3 wire top loading > wires - I've a couple of questions... > > 1. I see a recommendation that the vertical part of the Inv L aerial > wire(s) should be a single wire (ZL recommendation), or if not then three > or how many wires should converge to a single point at the bottom. Why is a > single wire recommended over a multiple? Em thinking losses into nearby > objects? Wouldn't a multiple vertical wire feed increase "good non lossy" > C and increase Ra? Yes, it will increase the C to ground, but you want this as high as possible. Three wires all the way up will give you C near the bottom which is bad news. > 2. Ive seen a large amount of schematics both for commercial and ham top > loading.of T and L's ...Say for a three wire top loading spaced 1m apart - > should the wires at the far/near end all be shorted together or left open? > Does this affect the total cap either way, or is it just for electrical > "circuit" stability?? Does it make any difference if they are shorted at > any point along the top?? Is there a recommendation which proves open > versus short is better ? I have done some crude experiments and have found little difference. However, I have found that the more you join together, the less there is to fall down if a single support rope fails. My three top wires are each supported by their own insulators and polyprop rope, but are shorted at the ends. If any two ropes break, the third will still support the antenna via the shorting wires (the top section will be bent but will work, at slightly reduced efficiency). Mike, G3XDV http://www.lf.thersgb.net ====================