[time-nuts] 10MHz Rubidium reference source for frequency counter

Charles Steinmetz csteinmetz at yandex.com
Fri Oct 31 23:40:04 EDT 2014


John wrote:

>It seems to me that it's just a case of expecting too much from a counter.

Possibly, but a well-tuned 5370B can get to the low e-12's at 1-10 
seconds.  It has better one-shot resolution than the Pendulum, but 
not by a factor of 10.  So, I'd have thought the Pendulum would at 
least get to the mid e-11's if the time base was up to it.

>To get the best performance from a counter, you need to set up the 
>trigger thresholds well away from ground as Charles says.  Also 
>consider taking TI readings rather than frequency 
>readings.  Frequency readings are OK for initial setup and basic 
>ADEV comparisons but they won't generally yield the best ADEV 
>fidelity or the lowest possible measurement floor.

Yes, using TI mode is essential for getting down to the counter's 
limits.  Was Karen using frequency mode?  I wasn't paying attention 
to that end of things.

Best regards,

Charles






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