"Clifton T. Sharp Jr." ) writes:
Warren wrote:
What's the capacitance of variable capacitors found in clock-radios ?
I want to make a pizza-box antena and can't find 10-365pF.

Some are 10-365. Some (mostly in small transistor radios) are 10-140. Ya
picks yer radio and ya takes yer chances.

But a lot of times, the "10-365pf variable capacitor" is just a generic
term, meaning take one out of an existing radio. They are specified because
they are available. Now, in this particular case the full capacitance
may be desired because of the resulting runing range of the loop,
but plenty of times you'd see this type of variable listed because it
was available and it worked. Whenever I see one specified, I immediately
know that it's not being used for anything precision. They tend to
be built cheaply, and I wouldn't use it in a VFO that I wanted best
performance from. So I would start using what I had at hand, or
even suggest someone pay a dollar at a garage sale (or rummage sale,
or even something like the Salvation Army) for an old radio to take
the variable capacitor out of, rather than spending the ten dollars people
are suggesting for just a capacitor. Plus, the capacitor gained this
way is available locally, rather than having to send away for it.

Michael