Frequency Reference Error Test - HP 8566B Adjustment Manual

10 MHz Standard Adjustment
Aging Rate: <l X 10mg/day and ~2.5 X 10s7 year; attained after 30
days warm-up from cold start at 25'C.
Temperature Stability: <7 X 1O-gOo to 55°C
Frequency is within 1 X lo-" of final stabilized frequency within 30
minutes.
The frequency of the spectrum analyzer time base oscillator is
measured directly using a frequency counter locked to a frequency
reference which has an aging rate less than one-tenth that of the
time base specification. After a 30-day warm-up period, a frequency
measurement is made. The analyzer is left undisturbed for a 24-hour
period and a second reading is taken. The frequency change over this
24-hour period must be less than one part in log.
This test requires that the spectrum analyzer be turned on (not in
STANDBY) for a period of 30 days to ensure that the frequency
reference attains its specified aging rate. However, after the aging
rate is attained, the frequency reference typically attains its aging
rate again in 72 hours of operation after being off for a period not
exceeding 24 hours.
Because the frequency reference is sensitive to shock and vibration,
care must be taken not to disturb the spectrum analyzer during the 24
hour period in which the frequency measurement is made.
The frequency reference should remain within its attained aging
rate if: the instrument is left on; the instrument orientation with
respect to the earth's magnetic field is maintained; and the instrument
does not sustain any mechanical shock. Frequency changes due to
orientation with respect to the earth's magnetic field and altitude
changes will usually be nullified when the instrument is returned to
its original position. Frequency changes due to mechanical shock will
usually appear as a fixed frequency error.
The frequency reference is also sensitive to temperature changes;
for this reason, the ambient temperature near the instrument at the
first measurement time and the ambient temperature at the second
measurement time should not differ by more than 1°C. Placing the
spectrum analyzer in STANDBY turns the instrument off while
continuing to provide power for the frequency reference oven, which
minimizes warm up time. However, the spectrum analyzer must be ON
to allow the frequency reference to attain its specified aging rate.

22. Frequency Reference Error Test

Performance Tests 2-87