Martin . . .
I second what Chris says regards GPS locking. For some time I viewed
it as a 'black art' but it is nowhere near as intimidating as it
sounds. Also, I would have to agree to some extent with Chris's hint
that the quality of crystals these days isn't what they are cut
(pardon the pun) out to be. I have a crystal cut for 40 deg.
operation that is somewhat 'unruly, but my 'cupido' PLL board soon
keeps it in check!! I'd go for GPS locking, you won't regret it!
--- In firstname.lastname@example.org, Chris Bartram <yahoo@...> wrote:
timing/frequency stabilisation applications are starting toapproach the
price of a decent custom crystal. It's now quite usual to find a10MHz output
on 'timing' GPS receivers. There are a number of reliable designsfrom eg.
CT1DMK and G4JNT which can be used to lock an existing crystaloscillator to
a stable source.experience -
which I can't talk about in detail - I've come to the conclusionthat the
performance of custom crystals from most suppliers is getting worseand worse
as the demand for them decreases.temperature
is not necessarily a Good Idea. It can work, but, crystals 'cut'for
operation at room temperature sit on an inflexion of theirrelatively
little with temperature over a few degrees. Trying to operate thecrystal at
an elevated temperature will place it on a slope, and it becomesmuch more
difficult to stabilise the frequency. Crystals cut for operation atelevated
temperatures are available, but even from 'professional' suppliers,they are
_much_ more susceptible to rapid aging effects than a roomtemperature
technique which used to be used very successfully by a number ofpeople, but
which seems to have been forgotten, was to bury crystal oscillatorsa metre
or so below the surface. At that depth the annual change intemperature is a
degree or so, and discounting aging effects, oscillators will driftvery