Return-Path: Received: (qmail 45075 invoked from network); 10 Mar 2005 19:49:21 -0000 Received: from unknown (HELO ptb-spamcore01.plus.net) (192.168.71.1) by ptb-mailstore03.plus.net with SMTP; 10 Mar 2005 19:49:21 -0000 Received: from mailnull by ptb-spamcore01.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1D9Thg-000B42-Ah for dave@picks.force9.co.uk; Thu, 10 Mar 2005 19:52:20 +0000 Received: from [192.168.67.3] (helo=ptb-mxcore03.plus.net) by ptb-spamcore01.plus.net with esmtp (Exim 4.32; FreeBSD) id 1D9Thg-000B3y-7N for dave@picks.force9.co.uk; Thu, 10 Mar 2005 19:52:16 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore03.plus.net with esmtp (Exim) id 1D9Tgs-0001jz-1P for dave@picks.force9.co.uk; Thu, 10 Mar 2005 19:51:26 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1D9Te5-0000kN-Pm for rs_out_1@blacksheep.org; Thu, 10 Mar 2005 19:48:33 +0000 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1D9Te5-0000kE-Ch for rsgb_lf_group@blacksheep.org; Thu, 10 Mar 2005 19:48:33 +0000 Received: from web25704.mail.ukl.yahoo.com ([217.12.10.176]) by relay.thorcom.net with smtp (Exim 4.43) id 1D9Te3-0007aN-UL for rsgb_lf_group@blacksheep.org; Thu, 10 Mar 2005 19:48:33 +0000 Received: (qmail 99077 invoked by uid 60001); 10 Mar 2005 19:48:26 -0000 Message-ID: <20050310194826.99075.qmail@web25704.mail.ukl.yahoo.com> Received: from [213.78.182.231] by web25704.mail.ukl.yahoo.com via HTTP; Thu, 10 Mar 2005 19:48:26 GMT Date: Thu, 10 Mar 2005 19:48:26 +0000 (GMT) From: brian hodgson To: rsgb_lf_group@blacksheep.org In-Reply-To: 6667 MIME-Version: 1.0 X-SPF-Result: relay.thorcom.net: 217.12.10.176 is neither permitted nor denied by domain of yahoo.co.uk X-Spam-Score: 0.3 (/) X-Spam-Report: autolearn=no,HTML_10_20=0.295,HTML_MESSAGE=0.001 Subject: Re: LF: Off topic Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: 8bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Status: No, hits=0.0 required=5.0 tests=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)
Hi Dick
 
Looking in my trusty "Reference Data for Radio Engineers" (won in a rally raffle at least 40 years ago !) the spark gap voltages chart indicates about 30 kV per inch for "needles" and between 55 and 80 kV for spheres spaced and inch apart (depending on the size of the spheres). Hope that helps.
 
Brian 

Dick Rollema <dickrollema@casema.nl> wrote:
TYo All from PA0SE

I am presently writing an article for our VERON magazine Electron  on the early radio experiments by Marconi. In these experiments spark gaps played an important role. Because I would like to perform some simple calculations on the peak power radiated by a spark transmitter I am looking for data on the break down voltage of spark gaps, consisting of two spheres.
In literature, found on the Internet, 75kV/inch is quoted but it is not stated whether this is between points or spheres and that makes a lot of difference.
Temperature and air pressure also influence break down voltage but I will forget about that, reckoning with "normal" conditions  of,
say , 20 degrees centigrade and  1000 hectopascal or whatever as reckoned as standard  barometric pressure.
Your help will be very much appreciated.

73, Dick, PA0SE
JN22GD

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