[evlatests] Master LO frequency references and the 1.7ms discrepancy

[Keith Morris]

As it stands now, the L356 firmware version that is installed at the site
accurately measures the drift, but not the offset, between the GPS and the
synthesized pulse.  We have been testing a new firmware version in the lab
in which we attempt to address the offset problem, but it is not yet ready
to deploy.




> It seems to me that the monitor point design must be changed to
> measure the lag between the L356 and the GPS, so this doesn't happen
> again.
>
>> We located the source of the 1.7 millisecond timing discrepancy.  The
>> GPS
>> 1PPS signal and the 1PPS signal generated in the L356 were
>> mis-synchronized by exactly this amount, with the L356 lagging in
>> time.
>> This is due either to the L356 having been synchronized to the wrong
>> mark,
>> or not having been synchronized at all.  We resynchronized the two
>> pulses
>> this morning at 11am.
>>
>> Then, at 11:40am, we switched the master frequency reference from
>> Hydrogen
>> Maser to Rubidium, as planned.  The PPS that is synthesized from the
>> Rubidium 5MHz is drifting relative to the GPS at a rate of about 9.8
>> microseconds/day.
>>
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>
>