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

Bob Camp kb8tq at n1k.org
Sun Nov 2 16:15:17 EST 2014


The fact that the plots are still going down (as 1/tau)  past the 1.0x10^-13 point at 1,000 seconds is also a pretty good indication that it's not really ADEV of an OCXO. 

The 100 ps rated single shot accuracy of the counter would give you 1.0 x10^-10 at 1 second and a 1/tau slope.


> On Nov 2, 2014, at 3:56 PM, Angus <not.again at btinternet.com> wrote:
> On Sun, 2 Nov 2014 12:13:34 +0300, you wrote:
>> Mode has been switch from Frequency to TI - result is much better now. It was the main improvement in my measurement. Thanks a lot!
>> Picture of ADEV OCXO result - https://dl.dropboxusercontent.com/u/21338179/hamradio/OCXO_Adev/OCXO%20ADEV%20TI%20mode%2020141102.jpg
> Hi Karen,
> You appear just to be measuring the ADEV of your counter in single
> shot TI mode here, not the oscillators - how exactly do you have the
> counter and oscillators connected up?
> If I was doing it I'd probably try start by setting the counter to
> measure freq in Smart Freq mode, and set it to ext ref, with one
> morion feeding the external reference and another on the input. If the
> morions are ok you should get towards 1E-11 at 1 sec (if I'm reading
> the specs correctly) If not, try other oscillators and see if anything
> changes.
> As John said, TI is more complex to do anyway, and with quartz that
> has not had days or even weeks to settle it's a total pain.
> Angus
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