[time-nuts] Question concerning ADEV measurements

[Robert Darby]

Thanks John and Magnus.

The reason I asked was that when I check the noise floor of my one and 
only 5370, the result is noticably superior using the external clock.  
Since the signal is coming from a single source fed through a MC ZFSC-2 
splitter and unequal lengths of co-ax, variability in the signal source 
should have no effect.  When I measure the 5370 with an external clock I 
see 2.24E-11 at t0=1s with a straight -1 slope; with the internal clock 
I see 4.43e-11 with periodic noise at about 11, 22, .... seconds.  This 
suggests to me that the internal oscillator is not so hot.

Having only one 5065 I want to use it to both clock the 5370 and serve 
as the reference; hence the question.  It seems to me by applying the 
DUT to the start channel one avoids the issue of hitting the same range 
of start values, assuming some phase change relative to the DUT.

Bob Darby


On 10/11/2013 5:36 PM, Magnus Danielson wrote:
> It can be a benefit or a cause of problem. In one end, it could lower
> your noise. The DG535 actually has that as a recommendation, that the
> signal source and the DG535 operate on the same clock.
>
> Another aspect is that you keep banging the same little range of values,
> and that may for that time-base to stop delay be systematically off in
> an unfavourable fashion. The noise of a counter is not always linear
> with that delay, so an asynchronous clock would sweep over the range.
> Then again, if the delay is just right you can utilize the minimum.
>
> Cheers,
> Magnus
>
> On 10/09/2013 11:42 PM, John Miles wrote:
>> Not sure if there's anything to worry about, but I don't think there are any
>> good reasons to do it.  The OCXO in the 5370 is an order of magnitude more
>> stable from one second to the next than the counter's resolution would allow
>> you to measure at t0=1s.
>>
>> -- john, KE5FX
>> Miles Design LLC
>>
>>> -----Original Message-----
>>> From: time-nuts-bounces at febo.com [mailto:time-nuts-
>>> bounces at febo.com] On Behalf Of Robert Darby
>>> Sent: Wednesday, October 09, 2013 12:30 PM
>>> To: time-nuts at febo.com
>>> Subject: [time-nuts] Question concerning ADEV measurements
>>>
>>> Is there a methodological difficulty using the reference clock to also
>>> clock a TIC?
>>>
>>> Specifically, I have a 5370B with the DUT on the start input and a 5065A
>>> on both the stop input and the external clock input.
>>>
>>> Thanks,
>>> Bob Darby
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