37.
a.
b.
Fig. 6-41. Typical equipment setup to check response flatness, sensitivity, frequency calibration and phase lock operation.
Adjust Band A Mixer Balance—Check
Amplitude of Spurious Signals from Internal
Sources
Equipment setup is shown in Fig. 6-40.
Connect a 50
Ω termination to band A RF INPUT con-
nector. Switch the band selector to A.
c. Adjust the GAIN control so noise amplitude is about
1 division.
d. Tune the RF CENTER FREQUENCY to the low end of
the dial against the stop. At this center frequency setting
with a dispersion of 2 MHz/div, a local oscillator feedthrough
spur should be visible on the display.
e. Tune the RF CENTER FREQUENCY to center the feed-
through spur, then decrease the dispersion to 1 MHz/div.
f. Adjust C14, C16 and R13 (band A mixer, see Fig. 6-39)
to minimize the amplitude of this feedthrough spur over the
5 MHz dispersion window.
g. Check through band A frequency range for spurious
signals. Amplitude of any spur with the exception of the local
oscillator feedthrough signal must not exceed
2× noise
amplitude. If a spur appears at approximately 37.5 MHz,
readjust the mixer balance.
h. Move the 50
Ω termination to band B RF INPUT con-
nector, switch the band selector to B and set the DISPER-
SION to 10 MHz/div.
i. Adjust the GAIN control for 1 division of noise, then
tune through the band B frequency range checking for spuri-
ous signals whose amplitude exceeds
2× noise level.
j. Move the 50
Ω termination to band C RF INPUT con-
nector. Set the band selector to C.
k. Check through the frequency range of band C for
spurious signals with amplitudes that should exceed
2×
noise level.
38A. Check Dial Accuracy, Analyzer Sensitivity
and Local Oscillator Phase Lock Operation
NOTE
Since signal generators with calibrated attenuators
are required to check sensitivity, dial accuracy
can be checked by the same instruments, provided
the signal source has an accuracy within 0.1%
at the dial check points. The signal generatars
listed in Table 6-9 may be used if their accuracy is
checked near each dial check point, by a frequency
counter or by the beat frequency indicator against
some accurate reference frequency.
6-40
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