I built two versions of a Colpitts VCO using red LEDs as varicaps.
Version one had too much load capacitance and the center frequency was
a few kHz below nominal. However, it had a fairly wide tuning range as
the LED was varied about 10p it would tune around 1kHz. A second version
had exactly the right base load capacitance (it oscillated within a few
Hz of 25MHz on powerup), but the tuning range using almost an identical
setup is much narrower.

Is this strong attraction to the natural Crystal frequency normal?

--
Ben Jackson AD7GD

http://www.ben.com/