[time-nuts] FMT on October 13

John Ackermann N8UR jra at febo.com
Tue Sep 25 08:04:23 EDT 2007

Didier Juges said the following on 09/24/2007 09:40 PM:
> ); SAEximRunCond expanded to false
> Errors-To: time-nuts-bounces+jra=fluffles.febo.com at febo.com RETRY
> I guess it depends on signal to noise ratio. With reciprocal counters, you
> only need one period to measure as acurately as you need, but to have good
> acuracy, you need very good S/N, as there is no filtering possible. 
> For example, the HP 5370 can measure a single period of a signal with a
> resolution of 20pS (excluding noise and trigger imperfections), so excluding
> these errors, the HP 5370 could measure a single period of a ~3.5 MHz signal
> with 7 x10-5 precision (if I have not goofed the calculations....) More
> periods improve the resolution proportionately to the quare root. Accuracy
> is another matter.

I did some measurements on the frequency counter capability of my 5370B
some time ago, and found that the performance wasn't as good as in time
interval mode.

But it's still not bad -- the internal noise floor was 4x10e-11 for 1
second (using the 1 second gate time).  See


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