Return-Path: Received: (qmail 18791 invoked from network); 19 Oct 2002 15:51:18 -0000 Received: from warrior.services.quay.plus.net (212.159.14.227) by mailstore with SMTP; 19 Oct 2002 15:51:18 -0000 Received: (qmail 22482 invoked from network); 19 Oct 2002 15:50:53 -0000 Received: from post.thorcom.com (193.82.116.70) by warrior.services.quay.plus.net with SMTP; 19 Oct 2002 15:50:53 -0000 Received: from majordom by post.thorcom.com with local (Exim 4.10) id 182vrv-0002mU-00 for rsgb_lf_group-outgoing@blacksheep.org; Sat, 19 Oct 2002 16:50:27 +0100 Received: from [62.253.162.43] (helo=mta03-svc.ntlworld.com) by post.thorcom.com with esmtp (Exim 4.10) id 182vrv-0002mL-00 for rsgb_lf_group@blacksheep.org; Sat, 19 Oct 2002 16:50:27 +0100 Received: from oemcomputer ([213.104.104.27]) by mta03-svc.ntlworld.com (InterMail vM.4.01.03.27 201-229-121-127-20010626) with SMTP id <20021019155025.IAFA292.mta03-svc.ntlworld.com@oemcomputer> for ; Sat, 19 Oct 2002 16:50:25 +0100 Message-ID: <000c01c27787$566bf080$1b6868d5@oemcomputer> From: "mike.dennison" To: rsgb_lf_group@blacksheep.org References: Date: Sat, 19 Oct 2002 16:50:58 +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: Ant Questions Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, hits=-1.1 required=5.0tests=EMAIL_ATTRIBUTION,REFERENCES,SPAM_PHRASE_02_03, USER_AGENT_OEversion=2.42 Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group G0CZD wrote: >I'm about to put up a 136kHz Antenna and have a couple of questions. >I don't have much space in the garden, approx 20m from the apex of the roof to a 20m high poplar tree in the opposite corner. I am considering an offset 'T' with a multi-wire top. >I am assuming (within practical limits) that as much capacitance as possible in the antenna is beneficial. It will resonate with lower inductance and therefore lower resistive losses. Yes, that is correct. >The RSGB LF experimenters h/b (p52) suggests that 2 wires separated by >100mm will provide 39% increase in capacitance. Is it safe to assume >that putting multiple wires up at 100mm will provide a compound >percentage increase? I am considering 6 wires at 100mm separation. Are >there any better solutions - I have neighbours I wish to remain on >speaking terms with... The capacity hat should be as wide as possible. This is more important that many wires. In fact, you quickly get into the law of diminshing returns with extra wires, plus the weight increases much faster than the capacitance. I use three wires over a total width of 1m. Making it wider would be better than having extra wires. >What effect does height have on the antenna? I can fairly safely get the >antenna up to 10m above ground level without too much difficulty. Will >there be any significant benefit to raising the tree end of the antenna >to say 15m. Yes. Height is all important as the ERP is directly related to the =square= of effective height. Effective height varies from 50% to 100% of the actual height depending on how good the top section is. Do not be tempted to droop the ends of any top wires. Good luck, Martyn. If you need to see a sketch of my antenna, which is 14m high by <18m long, it can be found at my web site. 73 Mike, G3XDV http://www.lf.thersgb.net ====================