[time-nuts] Brooks Shera's GPS standard or HP Z3801A??

Tom Van Baak tvb at leapsecond.com
Tue Apr 26 10:00:56 EDT 2005

> Why would it be cheaper than building Brook Shera's unit? You still need 
> all the same electronics, but a more expensive oscillator (I assume the 
> PRS10 is going to cost more than an HP 18011A.)

The data sheet for the PRS10 is at:

> How does the short term phase noise of the PRS10's compare with the HP 
> 10811A? I guess in the long term, they will both be the same if you link 
> them to a GPS source, but short term you have said will be dominated by 
> the crystal oscillator.

The ADEV for a PRS10 at 1 to 10 seconds is on the
order of 1e-11 making it 10x worse than the 10811
inside a Z3801A. So the choice depends on what
you want to use the output of your GPSDO for.

> I guess a current unit is likely to be better than a 20-30 year old one.

Not necessarily true. Some of the best oscillators in
the world were made 30 to 40 years ago. On the other
hand, you can't beat a PRS10 for features. Check out
the manual for the list of commands.


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