[Laser] stable audio oscillator?

[John Dalton]

I would have thought that for audio frequencies, the best non-oven controlled
crystals should be able to get stability in the range you mentioned.
A glance at Hy-Q (http://www.hy-q.com.au) shows they do crystals down to 3ppm.
(20khz * 3ppm) is less than 100mHz.

ALternatively, Electronics Australia once published a project for
the poor man's rubidium oscillator.  It involves draping a coil over
the back of a TV set to pick up the timing pulses from the TV signal
and using them to lock an oscillator.  For a portable system, I guess
you could even build a small TV receiver with its output being used
to lock an oscillator.  (According to EA, TV stations generally use
rubidium clocks to generate their signals.)

Alternatively, what about doing a similar thing with one of the 'radio
clock' systems out there.  GPS satellites carry very accurate clocks
(presumambly used to generate local oscillators).  What about using
the output of a GPS receiver to lock an oscillator?

Regards
John