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Message-ID: <5.0.2.1.2.20010115104331.00a06ec0@mail.pncl.co.uk>
Date: Mon, 15 Jan 2001 11:02:03 +0000
To: rsgb_lf_group@blacksheep.org
From: "Walter Blanchard" <blanch@pncl.co.uk>
Subject: LF: Coil Huts etc.
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My now-retired Decca engineer pal who had a lot to do with setting up coil 
huts and tuning coils, Nigel Fenner, tells me that he occasionally ran 
Decca transmitters without the copper lining in wooden coil huts but only 
in very dry climates. In the UK the prevailing dampness made it impossible 
to maintain tuning or coil "Q" and you would get corona all over the place. 
He warns against using ordinary soda-lime window glass for insulation - it 
is very lossy and will shatter,  the only glass that will stand up is 
Pyrex-type.  He says an excellent insulator he used many times was the 
largest Pyrex baking dish he could find with a hole bored in the bottom for 
the feeder. Also, ordinary plastic ropes (terylene, nylon, polypropylene 
etc) will melt. Either use steel wires broken up by many insulators or 
(expensively) sleeved Kevlar rope. And if you're going to run real power 
you MUST put in voltage limiters !   He thinks the fire in Dave's hut was 
probably caused by the plastic walls breaking down, getting hot and 
catching fire.
I could probably persuade him to come along to Beaumont for the next 
conference and give us a talk if you like.
Walter G3JKV.