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High voltage switch/relays for antenna?

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July 27th 06, 05:10 PM posted to rec.radio.amateur.antenna

Cecil Moore Cecil Moore is offline

Cecil Moore is offline

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First recorded activity by RadioBanter: Jul 2006

Posts: 1,614

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High voltage switch/relays for antenna?

wrote:
In this case when the relay is open he will have very high voltages
across the contacts even with very modest power. When the relay is
closed he will have a few amps of current at low power up to 5 or 10
amps at kilowatt levels.

I performed this same function in Arizona with a $5 relay.
There is a surplus store beside the freeway in South Phoenix.
They carry surplus relays from the local power company. Some
of those relays are high voltage rated. I choose a SPST relay
that had four contacts. Two contacts were about an inch apart
and, when energized, were shorted by an insulated shorting bar.
When not energized, there was a total of at least one inch of
air gap in the contact path, maybe more. The contacts were
about 1/4" in diameter.

I was running 100 watts. I borrowed a differential high voltage
scope and measured the peak to peak voltage between the ends of
my loop to be somewhat less than ~2500 volts. This was a full
wave 40m loop broken in the middle and tuned to resonance on 80m.
I tested it in increasing increments of 10 watts all the way to
100 watts with no problem. It was before the monsoon season so
the humidity was low. A couple of months later, a severe
thunderstorm broke my upper 2x2 support and brought the whole
thing tumbling down.
--
73, Cecil, http://www.qsl.net/w5dxp

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