im currently building an fm radio, and it calls for a variable capacitor. is that not just like a guitars tone control?
or do i miss the point(yet again)?

cheers :mrgreen:

Quote from: lightningfingersim currently building an fm radio, and it calls for a variable capacitor. is that not just like a guitars tone control?
or do i miss the point(yet again)?

cheers:mrgreen:

Afraid so
The guitar control (and others like it) varies the amount of a fixed capacitor value that the circuit "sees". The variable capacitor actually varies the capacitance. Hope that's somewhat clear.

-Eric

well, theoretically you could make a tone control with a variable capacitor.  most variable caps on the market today are 365 pF, which is not terribly large.  the cap in many guitars is .01 uF, which compares with 365 pF= .000365 uF.  so you can see the value is off by a factor of around 30... you'd have to build an active circuit of some kind to take advantage of that varying capacitance.

It's basically two conducting parts, made up of a couple of half-disks, with a thin non-conducting layer inbetween. You rotate one of your half-disks to vary the capacitance.