Variable Resonator Crystal

[airman00]

Anybody know if a variable resonator exists? and where I can buy it from?


EDIT: not like a radio which takes power to receive . I want to harness the piezoelectric effect from a variable source - basically get electricity from a variable resonance crystal  , or maybe a different medium

thanks,
eric

[izua]

check out TXCO - temperature controlled crystal oscillator.
variating the core temparuture variates the main frequency

[airman00]

hmmm


im looking for something that is variable crystal without putting in energy , like mechanical turning or something 

[555 timer chip guy]

you could put a variable capacitor in series with a the cristal it dos change the frequency to some extent but the best way to go is just use a 555 or if you need higher frequencies like 100KHz and up you could use a tank circuit witch is just a capacitor and an inductor in parallel you can change the frequency by changing the values of the inductor or capacitor.

[airman00]

I'm looking for a receiver for signals <30 hz

does that exist? thats why I want to be able to variably tune it

would the crystal and variable capacitor work?

[Steel_monkey]

30 Hz is too low. Why not just take MCU and generate required frequency with high resolution and accuracy?

[555 timer chip guy]

generally you should use at least 100kHz or more for RF. what are you using it for? I have many receiver schematics laying around if you like I can post one.