stevez said:
The simpler form of 'adjustable' crystal oscillator is probably VXO - just small variable capacitor that's adjusted by hand to get a little bit of range. I agree that replacing the variable capacitor with a varactor (or other) diode and a pot is still pretty simple.
Yes, VXO (Variable Xtal Oscillator) is the correct name, I've never seen VCXO used - and it obviously wouldn't apply to your original mention of a variable capacitor across a crystal!.
BTW, this technique is called 'pulling' a crystal, and as you say it only works over a very small range - and it also reduces the crystals accuracy somewhat.