Variable Caps -Reply

[Martin Czech]

> Many many years ago (like in the 80's man), my dad
> was helping me make a little radio tuner. We
> simply went to the local electronics store and
> picked up a variable cap designed for the purpose.
> It already had a dial attached to it. It was about
> an inch square, and half an inch high.
> 
> I'd be surprised if they don't make these any
> more, but if not, you can probably get one out of
> a Radio Shack crystal radio kit.
> 
Well, modern tuners have PLLs and VCOs and the like.  They use variable
capacitance diodes instead of costly mechanics.  These mechanical
things need quite exact manufacturing, the cap plates must fit very
good, otherwise you'll get a short, on the other hand the distance
between plates is reduced to minimum...  Most of these things have a
gear, one knob revolution is turned into 1/5 of the plate package or
so. Maybe you can try to find old radios to slay them...

m.c.