[time-nuts] Need HP 5061A setup help

Skip Withrow skip.withrow at gmail.com
Fri Mar 17 11:37:46 EDT 2017


Hello Time-Nuts,



I have an HP 5061A (relatively new chassis) with a very old Cs tube
installed (working) and I’m trying to wrap my head around the set up and
calibration of this unit, and just hoping for some help.



As a little background, HP changed the Zeeman modulation frequency, C-field
intensity, and A1 synthesizer frequency at serial number prefix 1336A.  This
is detailed in CHANGE 20 (pages 7-9 and 7-10) Model 5061A Manual Changes in
the 5061A Manual, and covered in much more detail in HP Service Note
5061A-9 (document 05061-9061 6/80-02).



                                    OLD                            NEW

Zeeman frequency            42.82kHz                    53.53kHz

C-field                          61 milligauss                      76
milligauss

Synth. Frequency            12,631,771.6 Hz            12,631,772.5 Hz



I can put the tube on frequency at the new synthesizer frequency by
changing the C-field current (closer to the old C-field value, by changing
A15R19).


1. The Zeeman modulation frequency is a complete mystery to me.  Is it
related to the value of the C-field that you are running?



2. If you are comparing the unit to GPS to calibrate it do you really care
what the Zeeman frequency is?  Adjust the C-field to put it on frequency
and call it a day?



I’m not sure if there was a physical change in the Cs tube as well.  But HP
mentions that the new values should have better stability.


3. Would I be better off changing the synthesizer frequency back to the old
value and adjusting the C-field (I would think lower) to put the unit on
frequency? My first thought is to leave well enough alone.



Thanks for any insight.

Skip Withrow


More information about the time-nuts mailing list