[time-nuts] Man with too many clocks.

[Bob Camp]

Hi

If your TCXO is off by 1 ppm, it will slip 10 cycles per second at 10 MHz. 
If it is off by 0.1 ppm it will slip a full cycle at 10 MHz. 
If it is off by 0.01 ppm *and* uses some sort of digital compensation, it will hop around.
If the GPS is not sawtooth corrected it will hop by a good fraction of a cycle at 10 MHz
If the GPS is not surveyed in and seeing many satellites, it may hop by more than a cycle at 10 MHz. 

Best bet:

Divide the TCXO down to a much lower frequency (< 100 Hz). Use the 5370 to look at the 
delta between the GPS pulse and the TCXO output.

Bob


> On Nov 3, 2016, at 9:22 AM, Peter Reilley <preilley_454 at comcast.net> wrote:
> 
> I am using the 1 PPS for the trigger.
> 
> Pete.
> 
> 
> On 11/3/2016 8:59 AM, Antonio A. S. Magalhaes wrote:
>> 
>> Pete,
>> 
>> Tell us about your trigger: where is it?
>> 
>> Regards,
>> 
>> Antonio/CT1TE
>> 
>> ---
>> 
>> A 2016-11-03 12:20, Peter Reilley escreveu:
>> 
>>> I am the proverbial man with too many clocks and I don't know what time it is.
>>> To correct this situation I have decided to calibrate everything.
>>> 
>>> I have a HP 5370B, a HP 6370A, and a HP 5328A all with the TCXO option.   I also
>>> have some TCXO modules.   I figured that I would calibrate them against my Trimble
>>> Resolution T GPS receiver.
>>> 
>>> I put the 1 PPS signal in one channel of my scope and one of the 10 MHz TCXO
>>> signals in the other channel and look at the phase relationship. The TCXO's are
>>> already close enough that I should not be out by more than a fraction of a waveform.
>>> I understand that I have to deal with the 1 PPS without sawtooth correction.
>>> 
>>> I expected to see the 10 MHz signal bounce around but not move more than 1/2
>>> of a wave length.   Instead I see the 10 MHz waveform appear steady for a few seconds
>>> then jump a significant portion of the wave.   The jump is too much to be confident
>>> that I have not slipped one cycle.
>>> 
>>> Can I do what I am trying to do or am I missing something?
>>> 
>>> Pete.
>>> 
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