Fig. 6-49. Local oscillator assembly showing drive shaft coupling
and tuning adjustments.
10. Set the frequency meter to 475 MHz. Tune the dial
tape to 275 and adjust the A band capacitance adjustment
See Fig. 6-48.
to tune the oscillator frequency
to 475 MHz.
4. Use an accurate frequency meter to check the oscillator
11. Repeat steps 9 and 10 until both frequency check
frequency and tune the band B local oscillator to 835 MHz.
points match the dial tape reading.
(Oscillator frequency can be checked by disconnecting the
Sealectro Connector J69 at the mixer output and connecting
12. Set the frequency meter to indicate 375.5 MHz. Tune
the oscillator output through an adapter cable to the fre-
the oscillator to 375.5 MHz. The frequency dial tape must
read between 174 and 177. If the tape does not read within
5. Check the dial reading for 635 MHz on scale 2. If
this range, both oscillators require special equipment to
calibrate and should be returned to Tektronix for repair and
dial is incorrect, loosen the set screws holding the coupling
between the drive shaft and the tuning shaft (see Fig. 6-48).
Tune the dial to read 635. This sets the dial tape to a known
frequency point on the tuning curve for both oscillators.
BAND B LOCAL OSCILLATOR
6. Check the dial tape tracking of the B band at several
points, including each end of the band. The oscillator fre-
quency must be within (1% of the dial tape frequency
This procedure requires that the band A local oscil-
plus 200 MHz).
lator be operating and tracking correctly. Both
band A and B covers must be in place and all
7. Switch the band selector to A.
screws must be tight.
8. Push the LOCK CHECK button and adjust the FINE
1. Set the band selector to band B. Push the LOCK CHECK
RF CENTER FREQ control for a centered trace or +7.0 V at
button and adjust the RF FINE FREQ control for a centered
the varactor bias terminal on band A local oscillator. See
display, or a varactor bias reading of 7.0 volts for band B
2. By means of a frequency meter or frequency counter,
9. Set the frequency meter to 210 MHz. Tune the dial to
set band B oscillator to 470 MHz. Note which side of 270
10 MHz and adjust the A band inductance adjustment (Fig.
on scale 2 the dial indicates.
to tune the oscillator freuency
to 210 MHz.