User's Manual

68P81093C75-A 9-43
Step 4. Using the torque driver and deep-well socket, loosen
the three tension nuts on the adjustment screws.
Step 5. De-tune the preselector as follows:
Turn tuning screws 3 and 4 clockwise until they bottom
out. Be careful not to apply more than 3 in. – lb. of
torque to prevent warping the preselector cover and
housing.
Step 6. Connect the test equipment as shown in Figure 15.
Tuning Procedure Step 1. Turn the station power supply ON (to provide the
active 50 Ω termination).
Step 2. Adjust the signal generator to the frequency calculated
on page 9-41. Set the level to +5 dBm.
Step 3. Insert the tuning probe into the cavity “U2” and adjust
tuning screw 2 for a PEAK.
Step 4. Tighten tension nut on tuning screw 2 to at least
12 in. – lb. and fine tune tuning screw 2 for a PEAK.
Figure 15. Test Equipment Setup for Preselector Field Tuning
From
Signal
Generator
RX
TX
Tension Nut
Tuning Screw
To Dip/Peak
Monitor
(RF Millivoltmeter
or Power Meter)
Tuning
Probe
To
Receiver
Board
To RX
Connector
on Top Panel
Preselector
Assembly
MAEPF-27040-O