[time-nuts] HP-5065A frequency adjustment advise and Common (all in) view GPS comparisons proposal.

[Edgardo Molina]

Dear Group,

Good afternoon. I just realized that my two HP 5065As have been running for about a month and their operation has been closely monitored. Now I assume both clocks are stabilized. I want to start doing some phase and time comparisons between them and with respect of a TrueTime 5 MHz GPS receiver signal. I only have an old Tracor 895A linear phase/time comparator for this purpose. Luckily it has 5 MHz as a frequency input.  At least it will allow me to get close to a decent synchronization as I continue searching for better measurement instruments. Next week I will be receiving my first HP 53132A and Prologix GPIB-USB interface to start characterising my clocks and doing Allan Deviation work.

My question here is how to finely adjust the 5065A frequency to bring it in phase to the 5 MHz GPS derived signal. I read somewhere that it can be fine tuned using the C Field control, but I am afraid of moving it as both controls have been set to each instrument's factory values. My oscillator fine frequency adjustment pots are set to 250 and locked there as per manual recommendation. May I get some advise as which is the best procedure to adjust these clocks to start matching them regularly to GPS reference? I just don't want to mess with the clocks during the process.

Also related to my previous question, is it common to use phase shifters with the 5065A not to touch the frequency standard adjustments? I saw NMIs using them to adjust Cs clock time scales without touching the Cs adjustments.

I would like to explore some interesting possibilities as a byproduct of this enterprise. Is anybody interested in common (all in) view GPS clock comparisons with me? I just learned the pro way of doing it at CENAM over the last couple of days during the symposia of time and frequency that I had the luck to attend. With some coordination there has to be a way to reproduce those experiences here, not only as isolated comparisons, but continuous periodic measurements. Probably automated in the future. I am afraid we will not be able to achieve legal traceability to UTC, as we are not doing this directly with an NMI or following a legal traceability chain to it. Or am I wrong? Does anybody has direct legal traceability using common view GPS with an NMI? Despite this, we could still build a network of inter comparisons using GPS as a way to continuously monitor our labs performance, just as the SIM network headed by NIST, NRC and CENAM do across the american continent NMIs. 

If the idea is welcome, please answer to the thread. I am more than enthusiastic. If there are currently efforts to achieve this, please accept my apologies for the lack of knowledge in the group's work. Still I would like to cooperate if possible. Other comments regarding feasibility and technical implications are surely welcome.

By the way, while attending the symposia, I noticed with pride that the Time-Nuts community is highly regarded among the crème de la crème Time and Frequency circles. Thank you all for allowing me to participate with the group.

Thank you!


Best regards, 



Edgardo Molina