100 mW, decrease the coupling by pulling the probe as-
calibration. See Maintenance Section.
The probe assemblies
sembly out. Tighten the set screws.
can be oriented within the magnetic
field of the oscillator
chamber by loosening set screws and
positioning the probe
i. Loosen the set screws (1) in Fig. 6-50, and position the
in or out of the chamber or rotating
the probe within the
plate choke for a frequency of 4.2 GHz.
field.
Force the lead screw against the bearing and tighten the
Usually the probes are rotated for maximum power output
set screws.
and inserted in or out of the chamber for the specified power
output. It is important to keep the output power below the
j. Loosen the set screws (2) in Fig. 6-50, and position the
maximum specification listed in steps 1 (m) and 1 (o) of the
cathode choke for maximum power output. Decrease probe
following procedure. All adjustments interact; therefore, as
coupling if power output exceeds 100 mW.
each adjustment is made, its effect on the frequency tracking
Force the lead screws against the bearing and tighten the
and output power over the frequency range of the oscillator
set screws.
must be checked. Adjust to obtain as flat an output as pos-
sible with frequency tracking within 1%.
k. Connect the Varactor terminal to a +1.5 V to +14 V
bias supply. The instrument bias supply is preferred. Set the
ALIGNMENT PROCEDURE FOR BAND C OSCILLATOR
Varactor bias voltage to +7 V and tune the oscillator to its
ASSEMBLY
mid-frequency position.
This procedure should be used only after replacing the
1. Vary the position of the Varactor assembly, until a bias
oscillator tube. Refer to Fig, 6-50 for the locatian of sub-as-
swing from +1.5 V to +14 V provides a frequency shift
semblies and parts. The oscillator assembly must be removed
equal to or greater than 1.5 MHz. Return the bias voltage
for calibration.
to +7 V, by adjusting the FINE RF CENTER FREQ control.
1. Alignment and Installation of the Probe and Varactor
m. Tune the oscillator through its frequency range checking
Assemblies.
the output power. Power output aver the range should not
exceed 100 mW or decrease below 5 mW.
a. Install probe assembly (Part No. 119-0107-01 into the
No. 2 port Fig, 6-50). Position the probe assembly approxi-
n. Remove the RF power meter from the No. 2 port and
mately 1/16 inch out from full penetration with the notch or
connect the meter through a 50 Ω 10 dB attenuator and 9
keyway (DC return of the probe towards the plate end of the
inch lossy cable to the No. 1 port. Connect the 9 inch (not
oscillator assembly, and secure by tightening one of the two
lossy) coaxial cable from the instrument-phase lock circuit to
set screws.
the No, 2 port.
CAUTION
o. Tune the oscillator through its frequency range checking
the output power from the No. 1 part. Power output should
Do not over-tighten set screws. They may warp
not exceed 16 mW or decrease below 2 mW.
the shaft if tightened too much.
Balancing the output of ports No. 1 and No. 2 may be
b. Install probe assembly (Part No. 119-0107-00) into the
necessary to provide the desired output from both ports. This
No. 1 port (Fig. 6-50]. Position the probe assembly approxi
is done by loosening the 2-56 set screw in the probe as-
mately 1/16 inch out from full penetration with the notch or
sembly ond varying the coupling. Each adjustment interacts
keyway towards the plate end of the oscillator assembly,
with the other adjustments, therefore, both outputs must be
and secure by tightening one of the two set screws.
checked after each adjustment.
c. Install the Varactor assembly (Part No. 119-01 05-00) into
2. Tracking the oscillator to the dial assembly.
the control port. Position the assembly approximately 1/16
inch out from full penetration and secure by tightening one
a. Tune the oscillator to 4.2 GHz. Set the indicated dial
of the two set screws.
assembly to 4.0 GHz and lock the dial assembly to the oscil-
lator tuning shaft.
d. Position the cathode and plate chokes to the high fre-
quency end of the band (towards the center of the assembly)
b. Tune the dial to indicate 1.5 GHz. Adjust the trimmer
but not against the stop.
screw (3) in Fig. 6-50, for an oscillator frequency of 1.7 GHz.
e. Connect an RF power meter through a 50 Ω, 10 dB at-
c. Repeat these steps until the oscillator frequency cor-
tenuator and a 9 inch coaxial cable (clear cable covering) to
responds to the dial reading at both ends of the frequency
the No. 2 port.
band.
f. Connect a frequency counter or accurate frequency
d. Check oscillator tracking through the frequency range.
measuring device through a 50 Ω termination and a 9 inch
Must track within (1% of the indicated dial reading
lossy coaxial cable (white cable covering) to the No, 1 port.
+200 MHz). It may be necessary to introduce some error at
the upper or lower frequency limits to bring the tracking
g. Apply power (B+ and filament supply) to the oscillator.
Allow approximately 10 minutes for the oscillator to stabilize.
within the 1% specification.
h. Loosen the set screw to No. 2 port and rotate probe
e. Check the phase lock operation over the frequency
range. Check for the presence of beat frequency signals and
assembly for maximum power input. Do not rotate the probe
stable locking operation.
180 from the preset position. If power output exceed
6-49
