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 on 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 on screen,
6) Slowly adjust the INT REF FREQ VARIABLE control.
Note the signal shift across the dispersion window as the
reference oscillator frequency is changed. Range of the
control is approximately 0.1% of the dial frequency. See
step 27.
f. Remove the signal and harmonic source from band B
RF INPUT connector and apply the signals to band C Co-
axial Mixer. Switch the band selector to C and set the DIS-
PERSION to 2 MHz/div.
g. Check dial accuracy over scale 4, band C. Check oscil-
lator and mixer operation and local oscillator phase lock
as the dial accuracy is checked. Check these parameters by
repeating the procedure described in step d for band B.
NOTE
There is no need to check dial calibration for the
upper scales of band C because they are multiples
of scale 4.
h. Apply 10 MHz (.1 s) marker signals and harmonics to
the band A RF INPUT. Switch the band selector to A. Set the
DISPERSION to 1 MHz/div.
i. Check the dial accuracy, oscillator and mixer perform-
ance, and LO phase lock operation through band A. Check
by using the same procedure that was used to check bands
B and C.
j. Check phase lock operation with an external reference
frequency. Use the procedure described in step 38A (k).
RF AND LOCAL OSCILLATOR CALIBRATION
NOTE
The following procedures are NOT part of the
routine calibration. They only provide a means
of calibrating the RF section after minor repair,
such as oscillator tube replacement. If possible we
recommend the complete RF assembly or the com-
plete unit be returned to Tektronix for repair,
See your local Tektranix Field Office or representa-
tive.
Dial Tracking
1. Apply power to the oscillator and allow 20 minutes
warmup time for the oscillator to stabilize.
2. Push the LOCK CHECK button and adjust the RF FINE
FREQ control for a centered (vertical) trace. This should
provide a varactor bias reading of +7.0 volts. See Fig. 6-48.
3. Use an accurate frequency meter or counter to tune
the A band oscillator to exactly 375.5 MHz (200 MHz above
a dial reading of 175.5).
6-45
