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