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12. Time Base Adjustment (SN 2848A to 3217A05567)
INT/EXT switch (rear panel) . . . . . . . . . . . . . . . . . . . . . EXT
7. On the Frequency Counter, select a 10 second gate time by
pressing,
(GATETIME_)
10
(GATE].
8. Offset the displayed frequency by -10.0 MHz by pressing,
MATH (SELECT/ENTER]
Cm)
10
I-1
6
[SELECT/E~&ER]
(SELECT/ENTER). The Frequency Counter should now display the
difference between the frequency of the INPUT A signal
(A27
10 MHz Frequency Standard) and 10.0 MHz with a displayed
resolution of 1 mHz (0.001 Hz).
9. Wait at least two gate periods for the Frequency Counter to settle,
and record the frequency of the
A27
10 MHz Frequency Standard
as reading
#l.
Reading 1:
mHz
Note
The
A27A2
Quartz Crystal Oscillator has a typical adjustment range of
10 MHz
*lO
Hz. The oscillator frequency should be within this range
after 48 hours of continuous operation.
10. Allow the spectrum analyzer to remain powered (not in
STANDBY) and undisturbed for an additional 24 hours.
11. Repeat steps 3 through 7 and record the frequency of the
A27
10
MHz Frequency Standard as reading
#2.
Reading 2:
mHz
12. If the difference between reading
#2
and reading
#l
is greater
than 1
mHz,
the
A27
10 MHz Frequency Standard has not
achieved its specified aging rate; the spectrum analyzer should
remain powered (not in STANDBY) and undisturbed for an
additional 24-hour interval. Then, repeat steps 3 through 7,
recording the frequency of the 10 MHz Frequency Standard at the
end of each 24-hour interval, until the specified aging rate of 1
mHz/day
(lxlOE9/day)
is achieved.
Reading 3:
mHz
Reading 4:
mHz
Reading 5:
mHz
Reading 6:
mHz
Reading 7:
mHz
13. Position the spectrum analyzer on its right side as shown
in Figure 3-54 and remove the bottom cover. Typically, the
frequency of the
A27
10 MHz Frequency Standard will shift
slightly when the spectrum analyzer is reoriented. Record this
shifted frequency of the
A27
10 MHz Frequency Standard.
Reading 8:
mHz
14. Subtract the shifted frequency reading in step 8 from the last
recorded frequency in step 7. This gives the frequency correction
factor needed to adjust the
A27
10 MHz Frequency Standard.
Frequency Correction Factor:
mHz
Adjustments
3-101