Return-Path: Received: (qmail 25865 invoked from network); 2 Aug 1999 09:06:34 +0100 Received: from magnus.plus.net.uk (HELO magnus.force9.net) (195.166.128.27) by guiness.force9.net with SMTP; 2 Aug 1999 09:06:34 +0100 Received: (qmail 22968 invoked from network); 2 Aug 1999 08:09:24 -0000 Content-Transfer-Encoding: 8bit Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by magnus.plus.net.uk with SMTP; 2 Aug 1999 08:09:24 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.02 #1) id 11BCyf-0007E3-00 for rsgb_lf_group-outgoing@blacksheep.org; Mon, 02 Aug 1999 08:57:45 +0100 X-Priority: 3 X-MSMail-Priority: Normal Received: from mailserv.cc.kuleuven.ac.be ([134.58.8.44]) by post.thorcom.com with esmtp (Exim 3.02 #1) id 11BCye-0007Dy-00 for rsgb_lf_group@blacksheep.org; Mon, 02 Aug 1999 08:57:44 +0100 Received: from LCBD15.fys.kuleuven.ac.be (LCBD15.fys.kuleuven.ac.be [134.58.80.15]) by mailserv.cc.kuleuven.ac.be (8.9.0/8.9.0) with SMTP id KAA11695 for ; Mon, 2 Aug 1999 10:03:38 +0200 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Message-ID: <3.0.1.16.19990802095858.2ca79558@mail.cc.kuleuven.ac.be> X-Sender: pb623250@mail.cc.kuleuven.ac.be X-Mailer: Windows Eudora Pro Version 3.0.1 (16) Date: Mon, 02 Aug 1999 09:58:58 To: rsgb_lf_group@blacksheep.org From: "Rik Strobbe" Subject: Re: LF: Summary of the OE Activity of July 31, 1999 In-reply-to: <37A47F3C.E268DAB6@qsl.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org Sender: >Questions: Does anybody know how to calculate/estimate/measure the >efficiency of our wire antenna to determine our ERP power? >Does anybody know of previous OE activities on 136kHz or is ours the >very first OE-DL contact as some of our QSO partners say? The antenna is rather unusual but if you look at it as a 'Marconi' then you should have an almost infinite topload (compared to the 13m vertical section). The radiation resistance of a short vertical monopole with infinite topload is Ra = 160 x (Pi * l/L)^2 where Ra = radiation resistance, Pi = 3.1415... , l = antenna height, L = wavelength and ^2 = squared. So as a 'wild guess' I would estimate Ra as 0.055 Ohms (55 milliOhms). Your ERP further depends on the antennacurrent (Ia) : ERP = Ra x Ia^2 73, Rik ON7YD Rik Strobbe ON7YD rik.strobbe@fys.kuleuven.ac.be Villadreef 14 B-3128 Baal BELGIUM (JO20IX)