Return-Path: <majordom@post.thorcom.com> Received: (qmail 11287 invoked from network); 18 Jan 2001 20:48:38 -0000 Received: from unknown (HELO warrior-inbound.servers.plus.net) (212.159.14.227) by 10.226.25.101 with SMTP; 18 Jan 2001 20:48:38 -0000 Received: (qmail 684 invoked from network); 18 Jan 2001 20:52:04 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by warrior with SMTP; 18 Jan 2001 20:52:04 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.16 #1) id 14JLvs-0003Tc-00 for rsgb_lf_group-outgoing@blacksheep.org; Thu, 18 Jan 2001 20:45:20 +0000 Received: from lepidachrosite.lion-access.net ([212.19.217.3]) by post.thorcom.com with esmtp (Exim 3.16 #1) id 14JLvr-0003TX-00 for rsgb_lf_group@blacksheep.org; Thu, 18 Jan 2001 20:45:19 +0000 Received: from w8k3f0 (1Cust123.tnt17.rtm1.nl.uu.net [213.116.128.123]) by lepidachrosite.lion-access.net (I-Lab) with SMTP id 6F604CB0BB for <rsgb_lf_group@blacksheep.org>; Thu, 18 Jan 2001 20:44:59 +0000 (GMT) Message-ID: <004f01c08187$5bfdc660$d6a174d5@w8k3f0> From: "Dick Rollema" <d.w.rollema@freeler.nl> To: rsgb_lf_group@blacksheep.org References: <3.0.1.16.20010118142719.33cf5a3e@mail.cc.kuleuven.ac.be> Subject: Re: LF: Caged Coils Date: Thu, 18 Jan 2001 20:45:40 +0100 MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2314.1300 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: <majordom@post.thorcom.com> To All from PA0SE Rik, ON7YD wrote: > The radiation resistance of a multiturn loop is : > > Rs = 31200 x (n x F / L^2)^2 > where Rs = radiation resistance, n = number of turns, F = loop area, L = > wavelength. > > For my loadingcoil n = 120 and F = 0.04m^2, so at a wavelength of 2200m the > radiation resistance will be about 30 nano-Ohm. Estimated radiation > resistance of my inverted-L antenna is about 40 milli-Ohm. > > Shielding the coil (done properly - avoiding short circuit turns) would > make my signal 0.000003dB weaker. I am not shure whether this calculation is applicable to a loading coil. The coil in a mobile antenna for the HF bands is considered to radiate as a linear conductor with a length equal to the length of the coil. I think this could also be the case for a loading coil at LF. So if the coil is 1 metre long (high) with its axis vertical it acts as a 1 m long vertical antenna and when at the bottom of a vertical antenna it makes the radiator 1 m longer. 73, Dick, PA0SE