Return-Path: Received: (qmail 13962 invoked from network); 12 Dec 2004 18:20:21 -0000 Received: from unknown (HELO ptb-spamcore02.plus.net) (192.168.71.3) by ptb-mailstore02.plus.net with SMTP; 12 Dec 2004 18:20:21 -0000 Received: from mailnull by ptb-spamcore02.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1CdYNh-0005be-54 for dave@picks.force9.co.uk; Sun, 12 Dec 2004 18:23:41 +0000 Received: from [192.168.67.1] (helo=ptb-mxcore01.plus.net) by ptb-spamcore02.plus.net with esmtp (Exim 4.32; FreeBSD) id 1CdYNh-0005bb-27 for dave@picks.force9.co.uk; Sun, 12 Dec 2004 18:23:41 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (Exim 4.30; FreeBSD) id 1CdYKT-0002sY-00 for dave@picks.force9.co.uk; Sun, 12 Dec 2004 18:20:21 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1CdYJ9-0005oy-Od for rs_out_1@blacksheep.org; Sun, 12 Dec 2004 18:18:59 +0000 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1CdYJ9-0005op-Ad for rsgb_lf_group@blacksheep.org; Sun, 12 Dec 2004 18:18:59 +0000 Received: from pop.gmx.de ([213.165.64.20] helo=mail.gmx.net) by relay.thorcom.net with smtp (Exim 4.41) id 1CdYJ6-0005SB-1w for rsgb_lf_group@blacksheep.org; Sun, 12 Dec 2004 18:18:59 +0000 Received: (qmail 17522 invoked by uid 65534); 12 Dec 2004 18:18:49 -0000 Received: from ambg-d9b97cd4.pool.mediaWays.net (EHLO pc) (217.185.124.212) by mail.gmx.net (mp002) with SMTP; 12 Dec 2004 19:18:49 +0100 X-Authenticated: #17603633 Message-ID: <002b01c4e076$ffa85080$d47cb9d9@pc> From: "Thomas Koelpin" To: rsgb_lf_group@blacksheep.org Cc: th.koelpin@fh-amberg-weiden.de Date: Sun, 12 Dec 2004 19:18:34 +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 V5.50.4133.2400 X-SPF-Result: relay.thorcom.net: domain of gmx.net designates 213.165.64.20 as permitted sender X-Spam-Score: 2.1 (++) X-Spam-Report: autolearn=no,HTML_20_30=0.474,HTML_MESSAGE=0.001,SARE_RECV_SPAM_DOMN0a=1.666 Subject: LF: Hoar-Frost and Antenna Losses Content-Type: text/html; charset=windows-1252 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,HTML_MESSAGE autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-Spam-Filtered: by PlusNet SpamCORE (v3.00) Content-transfer-encoding: 8bit

Dear LF Group,

last saturday morning we had the first hoar-frost this year at -6 degree centigrade. All the trees and bushes in the backyard looked beautiful and so did my 13-m-Marconi-antenna. Feeder and 33-m 4-wire-topload were coated by fragile white needle crystals rising the wire diameter from normally 1 mm to 4 or 5 mm.

Switching on the TX with te usual settings the antenna current had decreased from the normally 4.7 A (at frost) to 2.75 A! The antenna capacity remained nearly unaffected (about 660 pF), but tuning the loading coil showed a much broader maximum than without hoar-frost.

Some calculations showed the following values for the total loss resistance of the antenna system:

- no frost, normal conditions: R = 24 Ohms

- frost: R = 18 Ohms

- hoar-frost: R = 31 Ohms

According to some other measurements and observations these values should be rather realistic. The difference between no-frost and frost is well known and should mainly arise from the reduced losses in the greens - but where do the additional losses at hoar-frost come from? Could the hoar-frost be a lossy dielectric? There were neither visual corona effects nor seemed the hoar-frost be melted by the antenna current. Sunday morning it disappeared on itself and the antenna current rose again to the usual 4.7 A at -3 degree centigrade.

Anyone with a good idea?

73,

Tom, DK1IS