Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mh04.r1000.mx.aol.com (Internet Inbound) with ESMTP id F0E7338000081; Wed, 12 Oct 2011 05:00:19 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1RDuev-0000ma-On for rs_out_1@blacksheep.org; Wed, 12 Oct 2011 09:59:29 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1RDuev-0000mR-AB for rsgb_lf_group@blacksheep.org; Wed, 12 Oct 2011 09:59:29 +0100 Received: from nm4.bt.bullet.mail.ukl.yahoo.com ([217.146.183.202]) by relay1.thorcom.net with smtp (Exim 4.63) (envelope-from ) id 1RDuet-0004P0-Mf for rsgb_lf_group@blacksheep.org; Wed, 12 Oct 2011 09:59:29 +0100 Received: from [217.146.183.197] by nm4.bt.bullet.mail.ukl.yahoo.com with NNFMP; 12 Oct 2011 08:59:22 -0000 Received: from [217.146.183.205] by tm3.bt.bullet.mail.ukl.yahoo.com with NNFMP; 12 Oct 2011 08:59:22 -0000 Received: from [127.0.0.1] by omp1003.bt.mail.ukl.yahoo.com with NNFMP; 12 Oct 2011 08:59:22 -0000 X-Yahoo-Newman-Id: 384778.23473.bm@omp1003.bt.mail.ukl.yahoo.com Received: (qmail 11040 invoked from network); 12 Oct 2011 08:59:22 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=btopenworld.com; h=DKIM-Signature:X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Received:Message-ID:From:To:References:In-Reply-To:Subject:Date:MIME-Version:Content-Type:Content-Transfer-Encoding:X-Priority:X-MSMail-Priority:X-Mailer:X-MimeOLE; b=xwkhwb466NLK/iCj1YzoD3kfKuE/GynjckjOaMHjGvuIu29ufsJ9QcIS27yEQuslpMGvH9GKXGN5SdfzmcaQG2GfI8AknFiQqMh1P9vi3YUFT/yT8qjt8+UAwlAf4lJh/XMzNu1G95R1ReQWQDoentjULZ1MV/ZtETTa/ax1BTU= ; DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=btopenworld.com; s=s1024; t=1318409962; bh=BrF15JY1D9ixBGRkBIE9i/pVd2lMj426LRaGlyUXOAw=; h=X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Received:Message-ID:From:To:References:In-Reply-To:Subject:Date:MIME-Version:Content-Type:Content-Transfer-Encoding:X-Priority:X-MSMail-Priority:X-Mailer:X-MimeOLE; b=XvoHlsZaFreYKPjILewjmb6sER3ZhQxFMDVfOJhYDgVRDGyLc2tpdUuhtpXRASP7dO/zpJPku9rjoLoBgSyvaFFewlylXx5+7ZhSiz6npgvjaCTpVM2tP/ipNeWNsJflT1wZgnHrbRS8PiPfYUR0gEOIBocV4HX4OohLg4tz128= X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: oDZ.X98VM1lCRg0oEBCTrkAIvNHiS4D2sgYIQQxx9pdduIu ECr2hdRNVBY65mBirgtweX8qi6mXpI2_jo4_A_LcK5lu3FhB4JL0fPMLRcyR DXaPJ5nY.c67eUC_P8bY90L_FObbrIwrX.02l7mc0zOVLQaHJRsTdeLvP6J2 168xQuuqAGi9L2pX.JwbpcMMH86sNAHqWinNxs5BgtVE5aFS17ePDFTRKi8E uUqdKta9wgp7qPHSKAmLB6LrUWBVffOtMrB_6RC_pf_HGXZqlpz9e7WBtyQc 9JdaRjN2fGK9PV0LP0VxLTgFx.EDGWbTwHCwiamvXqwT26AV7QaDOoWVTXvZ tAJJxAidmxapxfP3W2s1uJA3OHMxaAnyHdJjhDSm5KwhrskbC1Nw0X1em00_ aA5ZxIS8ySCaxNdFjLw-- X-Yahoo-SMTP: Cxhli3eswBD1ozmtAojhjrja86kWx0Qm9tycD5QR1DKWrOLgjJcXkw-- Received: from JimPC (james.moritz@86.178.209.61 with login) by smtp815.mail.ukl.yahoo.com with SMTP; 12 Oct 2011 08:59:16 +0000 GMT Message-ID: <35DE38F5CF8A41F386C249F8372A5288@JimPC> From: "James Moritz" To: References: <4E91694C.8060900@orange.fr> <4E9169AD.8090609@wanadoo.fr> <4E918C0E.30401@freenet.de> <4E918FF1.1010407@iup.uni-heidelberg.de> <1318166502.15085.YahooMailNeo@web28106.mail.ukl.yahoo.com> <1849736542-1318171189-cardhu_decombobulator_blackberry.rim.net-208700020-@b1.c11.bise7.blackberry> <4E920BBA.9040200@iup.uni-heidelberg.de> <4E934A40.9040204@gmx.de> <006c01cc87ab$427234c0$4001a8c0@lark> <834DCCD1D3834F4CB4C171B7C30E85B4@AGB> <004801cc8809$63378d50$4001a8c0@lark> In-Reply-To: Date: Wed, 12 Oct 2011 09:59:21 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6002.18197 X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6002.18463 DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,UNPARSEABLE_RELAY=0.001 Subject: LF: Re: Arcing relays &c. Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=response Content-Transfer-Encoding: 7bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.1 required=5.0 tests=MISSING_OUTLOOK_NAME 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-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:488394048:93952408 X-AOL-SCOLL-URL_COUNT: 0 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m014.2 ; domain : btopenworld.com DKIM : fail x-aol-sid: 3039ac1d60d84e9557237a24 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none Dear Joe, LF Group, > Feeding this into 3 mH (X=2500 ohm at 137.8 kHz) gives 11.2 kV (17 kV > peak) so relays in series as suggested by G8FZK and G3NYK should work > well. It is a bit more complicated than that... if you have a number of relays in series, when the contacts are open there will be one or more isolated "floating" sections of conductor linking the open contacts. To ensure that the voltage is evenly distributed between the relay contacts, you would need to take steps to ensure that the potentials of these isolated sections are equal divisions of the total antenna voltage - this would mean adjusting the distributed capacitance in the relay wiring somehow. Also, the relay at the "hot" end will have the entire antenna voltage between contacts and coil, so coil-contact breakdown voltage would need to be much higher than the voltage rating for the contacts. > I'm puzzled by the 6pf/metre rule for monoploes. It seems the capacitance > of the monopole is much higher. This is a good first-order estimate for wire antennas - it is reasonably accurate for wires up to a few mm in diameter, but if the antenna element is a conducting mast, the diameter will be much larger, and C significantly higher too. Cheers, Jim Moritz 73 de M0BMU