Variable Capacitor Antenna

[Ampersand]

I need help guys.

I understand than an antenna, used with a capacitor, can act as another capacitor, changing the frequency of a signal (albeit only picofarads).

How would I go about making this into a circuit? And could someone possibly explain how it works?

 

[robm]

If you can't explain how it works, then for what ungodly reason would you want to do it for?

Capacitance simply refers to an object's (doesn't need to actually be a capacitor) ability to store electricity. I can't really think of why you would want to store electricity in an antenna, or why that would change the frequency (assuming you're talking about radio frequency.) But radio electronics aren't my thing.

 

[XCVG]

A variable capacitor is used for tuning in radios- the capacity is very low and they are useless for storing electricity. Not sure how it works, but I think they only let certain frequencies through or something. That said, adding a variable capacitor will not change the usable frequency range of an antenna. You have to make it longer, shorter, or base-load it with a coil.

 

[Ampersand]

I wasn't looking to use it in the way you guys are talking about. That is how the antenna of a Theremin works, it's a variable capacitor, and it changes the frequency of the circuit slightly to change the pitch.