Return-Path: Received: (qmail 29234 invoked from network); 22 Oct 2002 10:21:05 -0000 Received: from murphys.services.quay.plus.net (212.159.14.225) by mailstore with SMTP; 22 Oct 2002 10:21:05 -0000 Received: (qmail 19435 invoked from network); 22 Oct 2002 10:19:48 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: from post.thorcom.com (193.82.116.70) by murphys.services.quay.plus.net with SMTP; 22 Oct 2002 10:19:48 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 4.10) id 183w6o-0006tn-00 for rsgb_lf_group-outgoing@blacksheep.org; Tue, 22 Oct 2002 11:17:58 +0100 Received: from [213.218.77.55] (helo=cmailENV3.svr.pol.co.uk) by post.thorcom.com with esmtp (Exim 4.10) id 183w6o-0006te-00 for rsgb_lf_group@blacksheep.org; Tue, 22 Oct 2002 11:17:58 +0100 Received: from [62.21.129.107] (helo=w8k3f0.freeler.nl) by cmailENV3.svr.pol.co.uk with esmtp (Exim 3.35 #1) id 183w6n-0002ZT-00 for rsgb_lf_group@blacksheep.org; Tue, 22 Oct 2002 10:17:57 +0000 Message-ID: <5.1.0.14.0.20021022114543.009ed1c0@POP3.freeler.nl> X-Sender: FRE0000086604@POP3.freeler.nl X-Mailer: QUALCOMM Windows Eudora Version 5.1 Date: Tue, 22 Oct 2002 12:16:43 +0200 To: rsgb_lf_group@blacksheep.org From: "Dick Rollema" In-reply-to: <000001c2793a$fcd867a0$276336d2@xtr743187> References: MIME-Version: 1.0 Subject: LF: Re: Drooping top loading Content-Type: text/html; charset=windows-1252 X-Spam-Status: No, hits=0.3 required=5.0tests=BIG_FONT,IN_REP_TO,SPAM_PHRASE_00_01version=2.42 Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Content-transfer-encoding: 8bit To All from PA0SE

In order to find  the effect of drooping top load wires upon the radiation resistance I modelled an umbrella antenna using K6STI's antenna simulation program Antenna Optimizer.

The antenna modelled consists of a vertical wire of 10 m with at the top four wires of 10 m each in the directions N, E, S and W.  The wires include an angle of alpha degrees with the horizontal.  All wires have a diameter of 1.5 millimetres.  The antenna is erected over perfect ground.

Alpha         Rrad      Capacitance
(degrees)  (mohm)      (pF)

 0                        26                   256   (horizontal top wires)

20                       18                   254

40                       12                   250

60                         8                   237

80                         8                   175 

73, Dick, PA0SE
JO22GD