[time-nuts] Newbie question - what use is a Ruby?

Magnus Danielson magnus at rubidium.dyndns.org
Mon Oct 5 19:12:12 UTC 2009


Scott Burris wrote:
> Murray Greenman wrote:
>> 4. They are a handy adjunct to the GPSDO. Use the latter to calibrate
>> the former, and then you've a reference even if GPS is unavailable. The
>> Rb units also have very good short-term stability.
>>   
> So, how would you go about calibrating your Rubidium against your GPSDO?
> 
> Presumably you would wait until your GPSDO has not gone into holdover 
> for some
> "good" amount of time, whatever that would be.
> 
> Then my way would be to use the GPSDO as the external frequency 
> reference to
> either my Racal-Dana 1998 or HP5328A, apply the rubidium as input, and 
> adjust
> the C field for 10.00000* Mhz.
> But I'm sure that's not the time-nuts way of doing this. :-)  So what's 
> the right way?

Use the time-interval mode of the counters, log the time-interval over 
time and adjust the C field until the long-term drift in time interval 
between the reference and the oscillator cancels out.

Requires some divide-down thing, like the TADD-2 divide-box. Use the 100 
kHz output when comparing to the PPS signal of say a Thunderbolt or 
whatever is available.

Cheers,
Magnus



More information about the time-nuts mailing list