[time-nuts] GPSDO time constant
John Ackermann N8UR
jra at febo.com
Thu Jan 8 13:32:30 EST 2009
I mentioned in another post that I picked up a couple of militarized
FTS-4100 "fly-away" Cs units. These have an option installed that adds
an accelerometer to the OCXO; it's supposed to reduce G sensitivity by
at least an order of magnitude.
SAIDJACK at aol.com wrote:
> Hi Magnus,
> all depends - in an aircraft you have 6g+ turn-overs :)
> We make a version of our FireFly-II GPSDO with ultra-low-g sensitivity and
> ruggedization, that one you can run in a back-pack while doing skating-tricks
> on a ramp and you won't see much change in frequency. A bit more pricey on
> that OCXO of course.
> Most "standard" oscillators will have about 1-2ppb change after a turn-over.
> I have seen some that actually change the Crystal temperature when turned
> over, so you can see the initial frequency change due to gravity, then you see
> the operating current change, and the frequency slowly drift away as the
> temperature of the crystal is changed. Bad. Very bad.
> In a message dated 1/8/2009 09:29:41 Pacific Standard Time,
> brooke at pacific.net writes:
> Magnus Danielson wrote:
> . . .
>> Most labs would have issues with a 2g turnover. :)
>> Flipping oscillators that runs is evil and should be avoided at all
>> times. Should be in the rulebook for time-nuts.
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