[time-nuts] Reference oscillator accuracy

[Brian Kirby]

You will need a receiver to compare your references to.  It appears that 
LORAN will be shut off, so that leaves two services available, either 
WWV 60 Khz or GPS.  I do not use WWV any more, I can tell you about GPS.

To compare against GPS you will need a timing receiver, there are 
several available.  A lot of us got Motorola Oncore VPs, UTs, or M12+, 
The Rockwell Jupiter is one and there are several more.  They provide a 
1 PPS signal that is locked to the on board standards on the GPS 
satellite.  You put this signal in one input of a time interval 
counter.  You use a 1 PPS divider on your local reference and put its 
signal in the other input of the time interval counter.   You can record 
continuous or take daily 24 hour readings and derive your drift rates.

GPS corrections are published at NIST; 
http://tf.nist.gov/service/gpstrace.htm

You can also compare against a GPS disciplined oscillator.  In the long 
term it should be dead on, you will have to have it characterized for 
the short term.  The HP Z3801A was on the surplus market several years 
back, its probably one of the best.  The Trimble Thunderbolts were 
available to the group a while back. 

Brian KD4FM

Glenn Little WB4UIV wrote:
> While I was in the US Navy we had two Cesium standards for the 
> navigation center on SSBN submarines.
> While in port, we would track LORAN C and compute the drift rate of 
> the two cesium standards.
> Is there a service, that has drift rates published, that I can compare 
> my standards to, so that I can determine the standard drift rate.
> I do not remember the drift rates that we determined on the submarine, 
> that was a few years ago, but, I seem to remember that the rate was in 
> the low nanoseconds.
> If a rubidium standard drifts in one direction (does it?) a drift rate 
> could be calculated and, after a comparison to a known standard, with 
> known drift rate, a very accurate standard could be had for the lab.
>
> What would I expect the drift rate, or jitter, to be in a FRK class 
> rubidium oscillator?
>
> Is the drift rate constant enough that a drift rate could be applied 
> to a rubidium oscillator to determine it's real frequency at any given 
> time.
>
> We calibrated the submarine Cesium standards every three months.
> We had to know the drift rate of our standard as well as the drift 
> rate of the standard in each of the LORAN stations to be able to do 
> the type of LORAN navigation that we did.
>
> I would like to be able to verify that my PTB-100 rubidium oscillator 
> is on frequency.
>
> If I compare two rubidium oscillators, what would I expect the 
> relative drift rate to be?
>
> Thanks
> 73
> Glenn
> WB4UIV
>
>
>
>
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