Transmitter Power Amplifier V106

capacitor C132 sets the minimum capacity

supply through terminal V of plug P101

resistor R121, rf choke L119, and parallel-

point of Z108. Coupling loop L111 couples

the rf energy from Z108 and low-pass fil-

tuned circuit Z107.

b. The amplified output of V105 is de-

ter FL1101 to the antenna through contacts

veloped across tuned circuit Z107. Tuned

1 and 2 of antenna relay K101 and the direc-

circuit Z107, in parallel with capacitor

tional coupler (para 10). The screen grid

C145 and trimmer capacitor C141, is tuned

voltage of V106 is reduced by resistor R6.

to present a high impedance to rf signals

Rf decoupling is provided by C138 and

in the 225.0- to 399.9-mc range. Choke

L121. Low pass filter FL1101 attenuates

L119 and capacitor C142 form a plate de-

all frequencies above 400 mc to reduce

coupling network for V105. Resistor R121

harmonic output.

is a meter shunt for M701 (fig. 22) when

S704 is placed in the DVR Ib position.

58. Audio Input Circuits

(fig. 20)

56. Transmitter Power Amplifier V106

(fig. 19)

Figure 20 shows the interunit audio input

circuits for both Radio Set AN/VRC-24 and

a. The output of transmitter driver V105

AN/TRC-68. For normal transmission

is developed across Z107 and is coupled by

(NOR BB switch set to NOR), microphone

C128 to the grid of V106. Rf choke L114

audio signals from AUDIO jacks J702-C

provides a high impedance for the rf driv-

and J703-C are coupled through rf filter

ing signal. Resistor R108 and capacitor

FL702 to the audio amplifier and modula-

C146 provide grid-leak bias for V106. Re-

tor subunit through terminal F of P801.

sistor R109 is a meter shunt for M701

Audio signals from Radio Set Control C-

(fig. 22) when switch S704 is placed in the

1439/U or from the retransmit equipment

PA Ig position. Fixed-protective bias is

are coupled through rf filter FL19 to the

supplied through terminal T of P101. Jack

same input terminal. Microphone current

J111 is a test point for measuring the fixed

for the carbon microphone is supplied from

and grid-leak bias.

the -30-volt supply through terminal M of

b. The screen grid of V106 receives

plug P801 and the filter network that con-

modulated dc voltage through terminal N of

sists of capacitors C816 and C819 and re-

plug P101. Capacitor C138 and inductor

sistor R817.

L121 are a screen grid rf decoupling net-

work. Power amp1ifier V106 receives

modulated plate voltage through an insul-

59. Audio Preamplifier V803

(fig. 20)

ated conductor passing through the inner

conductor of coaxial cavity Z108, through

a. Audio input signals are amplified by

feedthrough capacitor C133, and terminal

audio preamplifier V803 and applied to

M of plug P101. Capacitor C133 bypasses

modulation driver stage V804. Microphone

rf signals from the +300-volt supply.

signals from terminal F of P801 are cou-

pled through switch contacts 7 and 9 of

57. Power Amplifier Output Circuit

S801A, coupling capacitor C809, resistor

(fig. 19)

R818, and R850 to the control grid of V803.

Resistors R820 and R819 are the grid-

The power amplifier output is developed

return bias circuit for V803. Bypass ca-

across plate tank Z108. The tuned circuit

is a coaxial cavity and an integral tuning

pacitor C817 limits the high-frequency

response of the preamplifier stage. Re-

capacitor that is ganged with the rf ampli-

fier tank circuits and is tuned by the 1,750-

sistor R821 and capacitor C811 provide

position shaft of the frequency selector.

cathode bias for V803. Screen grid voltage

Blocking capacitor C131 prevents the dc

for V803 is supplied from the +125-volt dc

plate voltage on V106 from being grounded

supply through voltage dropping resistor

through Z108 and couples the rf energy

R823. Capacitor C812 provides a low-im-

from the plate of V106 to Z108. Trimmer

pedance path to ground for audio signals on