Frequency Offset And Calibration - HP 5065A Operating And Service Manual

Model 5065A
Circuit Diagrams, Theory, and Maintenance
Figure 3-1. RVFR Pumping
HEWLETT^ M
POWER SUPPLY
1A, «.2Vdc
BLACK WIRE
A12P17
SEE NOTE
+ 1 —
1A
RED WIRE
NOTE: Instruments serial number 1732A00791 and above do not have the P17/J17 connector
but have the cable soldered. In this case, disconnect the wires and connect directly to
the power supply. Mating Connector for P17 is HP Part No. 1251-1113 (Winchester
Part No. JF1P-1-SA).
g. Turn on Power Supply and adjust voltage high
enough so output current can be set with current-limit
control. Read current on power supply meter.
h.
is 1A.
Set current-limit control so supply output current
i. Reduce voltage control setting so that it is just
above the point where further reduction would reduce the
power supply output current.
j. Recheck polarity of power supply connection to
A12P17. This must be properly connected.
k. Remove short from power supply output to allow
current to flow into the RVFR. Adjust power supply voltage
and/or current limit to bring current to 1A.
I. Reconnect 5065A to AC line. Set front panel
MODE switch to LOOP OPEN, meter switch to 2nd HAR­
MONIC. Allow power supply and 5065A to operate
continuously.
m. Within 12 to 48 hours signal should begin to
appear on 2ND HARMONIC meter. NOTE: the quartz
oscillator on the 5065A must be within about 1 X 10-7
of 5 MHz for the signal to appear. If possible, set the
5065A oscillator against a reference standard before
proceeding.
n. Check 2ND HARMONIC meter readings twice
per day until reading is greater than 10 or reaches a maxi­
mum. If this does not occur within 15 days then cell flood­
ing is not the problem.
o. When checking 2ND HARMONIC meter reading
also record meter reading in PHOTO I position.
p. When 2ND HARMONIC reading is maximum or
greater than 10, remove power from 5065A. Remove power
supply connection, and reconnect red wiretoXA4(1) and
the black wire to XA8(1).
q. Replace bottom cover and reconnect AC power
to 5065A. The 5065A internal circuit will now optimize
the rubidium in the RVFR. Operate the 5065A contin­
uously for about 1 week. The 2ND HARMONIC reading
should stabilize. If the meter stabilizes at greater than 25
the instrument can be returned to service. If the reading
is less than 25 perform adjustments described in para­
graphs 5-24 thru 5-31 in the 5065A Operating and Service
Manual.
3-10. FREQUENCY OFFSET AND CALIBRATION
3-11. The Rubidium Vapor Frequency Standard is a
secondary frequency standard with a specified long term
stability drift less than 1 part in 10
1
1 per month.
3-12. Over a period of time, it may be necessary to
check the offset that has accrued since last calibration
and recalibrate the instrument to a primary frequency
standard.
3-13. Frequency adjustment can be made after deter­
mining the frequency error with respect to a reference.
Front panel MAGNETIC FIELD control is then adjusted
tod correct any frequency offset.
3-2