[time-nuts] HP 10811 Response I Replies

[WarrenS]

Does your Mode B 10811 use a different xtral or same xtral, different 
frequency?
What does Mode B do better, ... and worse?
Why was it not used in the 10811?


When trouble shooting a freq stability problem, usually the more data the 
better.
What can really help to narrow down the cause or see the cause/effect,
is to study a High Speed (100+ sps), High Resolution (>1e-12) plot of the 
frequency change with time.
That way one can see if the freq change is instantaneous or happens in 
steps, is the change monotonic, if there is a time constant to the freq 
change what is the TC's value and shape, is the freq change in fixed values 
or random noisy steps and now and if the freq returns to the original value.
With a good freq plot, the source of the problem can often be narrow down to 
a single possible source.
And the best tool that I know of for making that kind of plot is a TPLL-2.0 
tester.

Here is a freq plot that has nothing to do with the existing problem,
It is just an example where a TPLL-1.0  freq plot is useful in identifying 
the source of some "noise".
<http://www.febo.com/pipermail/time-nuts/attachments/20100615/e4c25279/attachment-0001.gif>

and another example showing a plot of purposely induced "Noise" that only a 
few instruments could even measure:
<http://www.thegleam.com/ke5fx/tpll/disturb_zoom.gif>

ws

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> WarrenS wrote:
>>
>> I have to wonder if the unit being tested had its high impedance oven
>> control points lifted off the PCB board and on Teflon standoffs like the
>> production units?
>>
>> ws
>>
> It was a production unit, no modifications whatsoever.
> The oven change is an interesting theory; I never thought of that.
> I have a mode B 10811 on hand that I could use to test that theory.
>
> Rick Karlquist N6RK
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