Return-Path: Received: (qmail 19116 invoked from network); 26 Aug 1999 06:17:03 +0100 Received: from purple.force9.net (195.166.128.228) by guiness.force9.net with SMTP; 26 Aug 1999 06:17:03 +0100 Received: (qmail 1085 invoked from network); 26 Aug 1999 05:16:53 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by purple.force9.net with SMTP; 26 Aug 1999 05:16:53 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.02 #1) id 11JrVs-0004ub-00 for rsgb_lf_group-outgoing@blacksheep.org; Thu, 26 Aug 1999 05:51:48 +0100 Received: from mb06.swip.net ([193.12.122.210]) by post.thorcom.com with esmtp (Exim 3.02 #1) id 11JrVr-0004uW-00 for rsgb_lf_group@blacksheep.org; Thu, 26 Aug 1999 05:51:47 +0100 Received: from win95 (d212-151-111-230.swipnet.se [212.151.111.230]) by mb06.swip.net (8.8.8/8.8.8) with SMTP id GAA00910 for ; Thu, 26 Aug 1999 06:51:44 +0200 (MET DST) Message-ID: <001d01beef7f$06262200$e66f97d4@win95.swipnet.se> From: "Christer Andersson" To: rsgb_lf_group@blacksheep.org Subject: LF: Multiple Tuned Vertical reference Date: Thu, 26 Aug 1999 06:54:03 +0200 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 4.72.3110.5 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: In rec.radio.amateur.antenna, W8JI writes: On Mon, 23 Aug 1999 12:00:31 GMT, 2w8ji@contesting.com (Tom W8JI) wrote: >In the latest installations and rebuilds, VLF stations have removed >multiple downlead systems and improved efficiency. I'm sure I can did >some references. OK Nate. Unlike you, I'll be helpful and post a clear reference that does not reference myself and includes an A-B comparison at one site with only a grounding system change . 19-14 of the Antenna Engineering Handbook by Jasik. A 26 KHz VLF antenna at Marion, Mass in the USA used a mutiple tuned system. The average dry/wet efficiency was 15.6 percent, with ground resistance averaging .32 ohms but with variations up to .615 ohms in dry weather. The Air Force rehabilitated the system with a conventional radial system occupying the same overall area. Average efficiency became 23 percent. An exact quote: "With the same antenna, site, and expanse of ground system and at the same very low frequency, a generally radial ground system resulted in considerably less ground loss than had previously been obtained with a combination of multiple stars, parallel wire grids, and a complex overhead distribution and equalizing system." IMO, with a ham doing things "less perfect" than commercial ventures and on a much higher frequency than 20 KHz, he would be well advised to avoid all the complex theories about multiple distributed grounds. Especially since they don't work as well as a simple, straightforward system of radial wires occupying the same physical area. I'm sure this carries over to HF as well, at least my results and the results at two AM BC stations and reports from others using both "special" and conventional systems compared at one site all agree...the conventional system is better.