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.
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