that might be present. The plate supply of
1-16. Uhf Test Generator Module 1A5
+225 volts dc at 15 milliamperes is applied
to the automatic directjon finder (adf) equip-
ment in the aircraft (if so equipped) from
terminal El of power converter module 1A3
through terminals 12 and 10 of relay K1 and
The uhf test generator module consists of a
pin H of connector 52. In MK-731/ARC-51X
crystal-controlled oscillator, a tripler, and two
only, a plate supply of +175 volts dc at 80
milliamperes is applied to terminal E2, E6
grounded-grid amplifiers provide a constant
of uhf test generator module 1A5 from ter-
input impedance with excellent signal-plus-
minal E2 of power converter module 1A3
noise-to-noise ratio. The oscillator produces a
through terminals 8 and 9 of relay K1.
100-mc cw (continuous-wave) signal which is
These two voltages (+225 and +175 volts dc)
multiplied to a 300-mc cw signal by the multi-
are actually supplied from the same point in
power converter module 1A3.
tion can be accomplished because the two
a. The first stage is a grounded-grid, tuned-
voltages cannot be simultaneously supplied
plate, tuned-cathode, crystal-controlled oscil-
because of the wiring of relay K1. When
lator. Plus 175 volts dc is applied to the plate
relay K1 is energized by depressing the PTT
of tube V1A through the plate tank circuit,
switch, only +175 volts dc can pass through
relay K1 to uhf test generator module 1A5.
and the plate tank circuit begins to resonate.
When relay K1 is deenergized, only +225
The signal voltage developed in the plate
volts dc can pass through relay K1 to the adf
tank circuit is applied to voltage divider ca-
equipment in the aircraft.
pacitors C6 and C7. The voltage across C7 is
in voltage is due to the difference in loads
applied to the cathode tank circuit through
The +225-volt dc adf plate
crystal Y1 and thereby provides a very selec-
supply from power converter module 1A3 is
tive feedback signal to the cathode of V1A.
also applied to terminal 4 of TEST SELECT
This signal is amplified by tube V1A and
switch S1 through resistor R13.
coupled through capacitor C8 to multiplier
R12 forms a voltage-dividing network with
(tripler) tube V1B.
When TEST SELECT switch
S1 is set to +225V, meter Ml is connected to
b. The second stage, tube V1B, multiplies
the +225-volt dc line for testing purposes.
(triples) the output of tube V1A. The + 175
volts dc is applied to the plate of V1B through
c. AC Supply, 9.65-Volt.
a plate tank circuit. Negative grid bias is de-
(aux) audio test voltage is applied to the adf
veloped across grid-return resistor R3.
equipment in the aircraft (if installed) from
amplified 100-mc output of V1A is applied to
terminal 6 of transformer T2 through terminal
the grid of V1B. This 100-mc signal is tripled
E4 of power converter module 1A3 and volt-
to 300 mc, developed across the plate load tank
age-dropping resistors R8 and R17. Resistor
circuit that is tuned to 300 mc, and coupled
R17 is a variable resistor, so the output can
through capacitor C12 to the cathode tank
be maintained at 9.65 volts ac. The aux audio
circuit of tube V2.
voltage is also applied to FUNCTION SE-
LECT switch S1 as a dc voltage. This dc sup-
c. The third and fourth stages, V2 and V3,
ply also comes from terminal E4 of power con-
are amplifiers. The 300-mc signal from V1B
verter module 1A3, but it is filtered and rec-
is applied to the cathode of first amplifier V2.
tified in the network including diode CR2, re-
The amplified output from V2 is developed
sistor R15, and capacitors C1 and C2. When
across the plate tank circuit and
TEST SELECT switch S1 is in the AUX
through capacitor C16 to the cathode of second
AUDIO position, this voltage is applied to me-
amplifier V3. The amplified output from V3
ter Ml for monitoring.
is developed across its plate tank circuit and