Figure 4-8. +12-V Series Regulator, Simplified Schematic Diagram

TO 31R2-2GRC171-2

TM 11-5820-815-14

NAVELEX 0967-LP-544-5010

4-224. The rf filter is a tunable bandpass filter that

Resistor R30 is test selected to set the output voltage to

provides a high degree of selectivity between the

approximately +22 V dc. The output current from the 22-

antenna and power amplifier or antenna and receiver.

V series regulator is not current limited.

The rf filter module includes the rf filter, mechanical drive

train, and servo motor with position feedback

4-221. RF FILTER MODULE A7.

potentiometer, whereas d/a servo amplifier module A1

provides control to the servo motor to position the rf filter

4-222. Refer to the block diagram of figure FO-9 and

to the desired frequency.

schematic diagram of figure FO-24 while reading the

following circuit descriptions.

Unless otherwise

4-225. The directional coupler senses forward and

specified, reference designators apply to components of

reflected power into the antenna during transmit mode.

rf filter module A7.

Outputs from the directional coupler are amplified and

fed back to the power amplifier module A8 for automatic

4-223. GENERAL. Refer to figure FO-9. Rf filter

load control and to the meter circuit on the front panel of

module A7 contains a transmit/receive switch, rf filter,

chassis A10. Percent modulation, derived from the

and directional coupler. The transmit/receive switch

forward power output, is fed to the meter circuit.

consists of three pin diodes (transmit series diode,

receive series diode, and receive shunt diode) that

4-226. TRANSMIT/RECEIVE SWITCH AND CONTROL

together function as a transfer switch and receive signal

CIRCUIT. Refer to figure FO-24. Transmit series diode

attenuator. In transmit mode, the transmit series diode

CR1, receive series diode CR2, and receive shunt diode

provides minimum attenuation to the transmit rf signal

CR3 are pin-type diodes that exhibit the characteristic of

while the receive series and receive shunt diodes provide

providing an increasing rf resistance as the dc current

about 36 dB of isolation between the antenna and

through the diodes decreases. Maximum resistance is

receiver. In receive mode, the receive series and

attained when the diodes are reverse biased. Minimum

receive shunt diodes provide from 0- up to about 36-dB

resistance is attained when CR1 is forward biased at

attenuation for AGC control and receiver overload

about

100

protection. The transmit series diode provides about 20

dB of isolation between the antenna and power amplifier.

4-40