Uhf Test Generator Module 1A5 - TM-11-6625-564-450017

C2,TM 11-6625-564-45

that might be present. The plate supply of

1-16. Uhf Test Generator Module 1A5

+225 volts dc at 15 milliamperes is applied

(MK-731/ARC-51X Only)

to the automatic directjon finder (adf) equip-

ment in the aircraft (if so equipped) from

terminal El of power converter module 1A3

(fig. 4-8)

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

The

grounded-grid

amplifier

stages.

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.

This condi-

plier stage.

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.

The difference

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

being supplied.

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.

Resistor

coupled through capacitor C8 to multiplier

R12 forms a voltage-dividing network with

(tripler) tube V1B.

When TEST SELECT switch

resistor R13.

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.

The auxiliary

a plate tank circuit. Negative grid bias is de-

(aux) audio test voltage is applied to the adf

veloped across grid-return resistor R3.

The

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

coupled

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