I've got a non-parameter-related one:

A design which I'm looking at improving uses a 2.560MHz crystal in an HC6/U can as part of a timebase reference oscillator. Needless to say, this sucker drifts...the rig which incorporates the circuit has always been known for it. Say, 1.6KHz from a cold start.

So...I have a few options:

1) Temperature compensation of the existing crystal
2) Design a separate TCXO operating at 10.240MHz then divide it by 4 to reach the initial frequency
3) Find an HC-18/U version of the 2.560MHz crystal and temp-compensate that
4) Incorporate a circuit which applies +5v to the existing oscillator at all times, thereby keeping it in a stable thermal regime
5) Chuck the crystal oscillator altogether and replace it with an AD9851 or similar DDS, controlled by a PIC
6) ???

Give me your thoughts, Jerry.