Fig. 6- 45. Alternate equipment setup that will check dial accuracy, mixer and oscillator operation, and LO phase lock effectiveness.
38B. Alternate Procedure to Check Dial Accur-
acy, Oscillator Mixer Operation and Ef-
fectiveness of Local Oscillator Phase Lock
a. Equipment setup is shown in Fig. 6-45.
b. Apply 100 MHz (10 ns) markers from the marker output
of the time-mark generator through the harmonic generator,
the 200 MHz trap, and the 20 dB attenuator to the band B
RF INPUT connector.
c. Switch the band selector to B. Set the DISPERSION to
2 MHz/div and switch the VERTICAL DISPLAY selector to
LOG.
d. Check the dial accuracy as follows:
1) Tune the RF CENTER FREQUENCY through the band.
Observe the 100 MHz harmonics and their image spurii as
they travel across the screen towards the center and merge
with the IF feedthrough response, as the dial crosses a fre-
quency check paint. The harmonics then separate and move
off the screen. See Fig. 6-46. Maximum error between the
dial readings and frequency check points must not exceed
± (2 MHz + 1% of the dial reading).
2) Adjust the MIXER PEAKING control to optimize signal
amplitude. Note the spectral display of the harmonic genera-
tor signals. Tune the RF CENTER FREQUENCY through the
band, checking for dead spots which could be caused by
either local oscillator failure or mixer malfunction. The MIXER
PEAKING must be peaked at all check points.
e. Check-Local oscillator phase lock operation as follows:
1) Turn the INT REF FREQ control on. Decrease the DIS-
PERSION to 500 kHz/div.
2) Depress the LOCK CHECK button and adjust the FINE
RF CENTER FREQ control to position the display to the center
of the graticule area. Release the LOCK CHECK button.
3) Shift the IF feedthrough rsponse approximately 2 divi-
sions off center with the IF CENTER FREQ control, then tune
the RF CENTER FREQ to any harmonic signal. Depress the
LOCK CHECK button and adjust the FINE RF CENTER FREQ
control to establish a lock mode on the harmonic signal. See
Operating instructions.
4) Decrease the DISPERSION to 50 kHz/div, keeping the
signal centered an screen with the IF CENTER FREQ control.
5) Slowly adjust the FINE RF CENTER FREQ control until
the LO loses its lock. The signal may shift screen when the
LO loses phase lock. Re-establish phase lock by adjusting the
FINE RF CENTER FREQ control to return the signal an screen.
6-44
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