On Sat, 16 Jul 2005, Jim wrote:

Date: Sat, 16 Jul 2005 13:08:18 -0500
From: Jim
Newsgroups: rec.radio.amateur.homebrew
Subject: build a variable capacitor

i need a variable for a receiving loop antenna. does anyone know how to
determine the area of plates for a given value of cap? for example i
need 365 pf. two half circle plates would be handy, separated by a piece
of plastic or card stock. what surface area for each plate would
approximate that value? does two stator plates with one rotor between
them increase the value if compared to one plate each?



Do you really need to build this? I know they (365 mfd variables) are hard
to find (I'd love to find a cheap source, expensive sources on the
internet want $10-15 each [google on "365 mfd" to find them]), but if you
go to a thrift store (Salvation Army, etc.), you may find old transistor
clock radios for $1-2 each that have miniature 365 mfd variables that will
do just fine if you take a few minutes to de-solder them from the circuit
board.


Art, W4PON