[time-nuts] Sensitivity to g in atomic clocks

Bob Camp lists at rtty.us
Tue Jan 11 12:22:54 EST 2011


Hi

There are three things people refer to as G sensitivity on a crystal
oscillator:

1) 2 g tip sensitivity (flip it 180 degrees on the bench).
2) Vibration sensitivity (vibration translates into phase noise)
3) Relativistic effects (take the oscillator to the moon and it's frequency
changes).

The first does not apply to an atomic clock. Since (unlike quartz) they are
sensitive to magnetic field, they will change when you flip them around, but
for other reasons. That would make actually proving a "no sensitivity" spec
difficult. 

The second will not impact the atomic transition in an atomic clock
directly. Since they have narrow loops in them, it will impact the quartz
oscillators in the atomic clock. You will indeed see vibration translate
into phase noise at a ~ 2x10^-9/g sort of rate. 

The third does indeed apply to atomic clocks. Change the gravity and time
changes. Change time and there goes frequency. This is a very real part of
the spec process on space flight atomic clocks. I've never seen it worried
about on crystal oscillators for space applications. 

Bob 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of iovane at inwind.it
Sent: Tuesday, January 11, 2011 8:49 AM
To: time-nuts at febo.com
Subject: [time-nuts] Sensitivity to g in atomic clocks

While sensitivity to g is an usually specified parameter for crystal 
oscillators, I've been unable to find any indications for atomic clocks, say

5071A, or more modestly LPRO. Can anybody point me to any source of info on
the 
subject?
Thanks,
Antonio I8IOV

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