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Re: charged parallel plate capacitor



I've never heard of a vacuum capacitor for a receiver; they're not
inexpensive.

bc Who built his first "crystal set" in ca. 1946.

P.s. Still not that uncommon (square law variable caps.), but mostly replaced
by varactor diodes, if not by digitally synthesized local oscillators.

Bob Sciamanda wrote:

Is there such a thing as a capacitor
with a vacuum between the plates?

Not just in transmitters!
I'm sure we are not all so young that no one remembers the variable air
capacitor which was commonly used to tune consumer radios in ancient days
(perhaps even as late as the fifties? :) One can still find them in some
crystal radio kits for children.

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor