Return-Path: Received: (qmail 1263 invoked from network); 16 Sep 1999 13:06:21 +0100 Received: from magnet.plus.net.uk (HELO magnet.force9.net) (195.166.128.26) by guiness.force9.net with SMTP; 16 Sep 1999 13:06:21 +0100 Received: (qmail 26571 invoked from network); 16 Sep 1999 12:10:33 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by magnet.plus.net.uk with SMTP; 16 Sep 1999 12:10:33 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.02 #1) id 11Ra8C-00050Y-00 for rsgb_lf_group-outgoing@blacksheep.org; Thu, 16 Sep 1999 12:55:16 +0100 Received: from [143.179.236.32] (helo=Lesothosaurus.big-orange.net) by post.thorcom.com with esmtp (Exim 3.02 #1) id 11Ra8B-00050T-00 for rsgb_lf_group@blacksheep.org; Thu, 16 Sep 1999 12:55:15 +0100 Received: from w8k3f0 ([143.179.151.38]) by Lesothosaurus.big-orange.net (Netscape Messaging Server 3.6) with SMTP id AAA523A for ; Thu, 16 Sep 1999 13:55:10 +0200 Message-ID: <005a01bf003b$63e6be00$7497b38f@w8k3f0> From: "Dick Rollema" To: rsgb_lf_group@blacksheep.org Subject: Re: LF: LF-antenna with top load Date: Thu, 16 Sep 1999 14:01:58 +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: Mike, G3XDV wrote: > 1. No top load > Efficiency: 10.8% > 2. One horizontal top load wire of 5 m Efficiency: 12.5% > > 4. One horizontal top loading wire of 10 m Efficiency: 11.9% > 6. One horizontal top loading wire of 20 m > Efficiency: 10.0% Dick, There's something wrong here isn't there?. You have a reducing efficiency for increasing top load length. Surely that can't be right. Yes, I agree it looks strange. But it results from the way efficiency is calculated: radiation resistance divided by the sum of radiation and loss resistance. When the loss resistance increases more than the radiation resistance efficiency goes down. In the real world the actual efficiency will certaily get better as the small increase of wire loss is almost swamped by the total resistance of the system: earth loss + coil loss + wire loss. What really matters is the increase of Rs. It is better to ignore the efficiency figures; I used them only to calculate Rs from the real part in Z = R + jX 73, Dick, PA0SE