Figure 4-5. Frequency Synthesizer Transmit-Receive Switch, Simplified Schematic Diagram

TO 31R2-2GRC171-2

TM 11-5820-815-14

NAVELEX 0967-LP-544-5010

4-72. POWER SPLITTER. Capacitor A2A4C11 (figure

proximately 29 milliamperes. For the other two stages,

FO-19, sheet 3) couples the output of the selected vco to

resistor R8 sets the collector current of Q4 at

the power splitter which separates the vco signal into two

approximately 29 milliamperes, and resistor R12 sets the

signal paths. One signal path feeds output amplifier

collector current of Q6 at approximately 51 milliamperes.

circuit A2A6 through -12-dB pad A2A4R12-R13-R14.

In the rf path, variable capacitor C1, variable capacitor

The other signal path feeds the regenerative divider

C5 in series with inductor L3, and variable capacitor C8

circuit of the variable divider through -15-dB pad

in parallel with inductor L4 allow adjustment of the 3-

A2A4R11-A2A7R21-R22-R23. Besides separating the

stage rf amplifier for maximum flatness over the

vco signal, the power splitter provides isolation between

frequency range of the synthesizer. In the base circuit of

the half frequency of the regenerative divider and vco

Q2. capacitor C23 compensates for lead inductance of

signal being fed to power amplifier circuit A2A6.

Q2. In the t12-V dc circuit, inductors L10, L5, andL2and

capacitors C11, C7, and C4 form a decoupling network

4-73. OUTPUT AMPLIFIER A2A6. Reference desig-

to decouple the rf amplifier from the +12-V dc line. At the

nators apply to output amplifier A2A6, Output amplifier

output of rf amplifier Q6, the signal is coupled through

A2A6 (figure FO-19) consists of a 3-stage rf amplifier (rf

C10 to the transmit/receive switch and is loosely coupled

amplifiers Q2, Q4, andQ6 and associated bias amplifiers

through capacitor C12 to detector diode CR1. The dc

Q1, Q3, and Q5) followed by a diode type (CR2 and

voltage developed across CR1 is brought out to the pll

CR3) transmit/receive switch. In the 3-stage rf amplifier,

output (testpoint 4 on chassis A10) to give an indication

bias amplifiers Q1, Q3, and Q5 set the collector currents

as to the level of rf at the input to the transmit/receive

of Q2, Q4, and Q6 respectively. Since all bias amplifiers

switch.

function the same, only bias amplifier Q1 will be

discussed. The voltage divider R2-R3 sets the base

4-74. TRANSMIT/RECEIVE SWITCH.

Reference

voltage of Q1 at about 9.4 V dc which fixes the emitter

designators apply to A2A6. The transmit/receive switch

voltage at about 10.0 V dc. The resulting voltage drop

(figures FO-19 and 4-5) enables either the transmit rf

(about 2 V dc) across R4 sets the collector current of Q1

output of the synthesizer or the receive injection output.

at ap-

In transmit mode, a logic 0 key 2

Figure 4-5. Frequency Synthesizer Transmit-Receive Switch, Simplified Schematic Diagram

4-17