w5kcm wrote:
I am building a crystal tester and the circuit calls for two 220pf
caps in the oscillator. I didnt have any of these caps in the junque
box so I thought about making a couple gimmick caps. I understand this
is done by twisting some insulated wires together. Is there some guide
to use that will give you an approximate value? In other words, if I
have twisted some #26 enameled wire together does 1" equal some pf
value? Any info you may have on this will be appreciated.
w5kcm
"Gimmick" capacitors are only good for a few pf, and are
used to do light coupling or introduce
feedback/self-oscillation. even if you could build one, it
would be pretty unstable for test use. 220 pf is
substantial (an air capacitor would have many plates). In
the day, we'd use silver-mica type capacitors for stability.
If other friends' junque boxes are available, I'd try
those. Thank goodness for modern meters--at my age, reading
the color codes is hard!
--W9NPI