Agilent Technologies 8360 L Series, Service Manual

Page: 261 / 603

1. 10 MHz Standard
Description and Procedure
This pro cedure adjusts the frequency accuracy of the in ternal 10 MHz time base. This
adjustmen t should b e done on a regular basis if absolute frequency accuracy is imp ortant (see
Figure 3-3.)
F or b est accuracy , readjust the 10 MHz timebase oscillator after the syn thesizer has b een
on or in standb y for 24 hours. See \Accuracy V ersus Adjustmen t In terv al," following this
adjustmen t, for information on ho w to determine a p erio dic adjustmen t sc hedule.
After the timebase is adjusted, the timebase frequency should stay within the aging rate if the
follo wing things happ en:
The time base o v en do es not co ol do wn.
The instrumen t k eeps the same orientation with resp ect to the earth's magnetic eld.
The instrumen t stays at the same altitude.
The instrumen t do es not receiv e an y mec hanical sho c k.
If the time base o v en co ols (the instrumen t is disconnected from A C p o w er), y ou may ha v e to
readjust the time base frequency after a new w arm-up cycle. T ypically , ho w ev er, the time base
frequency returns to within 61 Hz of the original frequency .
Note
Y ou can adjust the in ternal timebase after reconnecting A C p o w er for 10
min utes, but for b est accuracy , test again after the instrumen t has b een on or
in standb y for 24 hours.
F requency c hanges, due either to a c hange in orientation with resp ect to the earth's magnetic
eld or to a c hange in altitude, are usually eliminated when the instrumen t is returned to its
original p osition. A frequency c hange due to mec hanical sho c k usually app ears as a xed
frequency error.
3-4 Adjustments
10 MHz Standard
Agilent 8360