Section III. ANTENNA COUPLER CU-2229/URC-92 FUNCTIONAL OPERATION

TM 11-5820-873-34

1A5A4L2 and 1A5A4C6) make up the ACC detector.

each of the four filter module boards. Wafer switch

Variable capacitor 1A5A4C13 tunes the circuit for heat

1A5A4S1 rotates until the open position reaches the

operation. The detector output at this point has a fast

hand position supplying the + 12 V. At that point + 12 V

rise/fall time. To maintain a constant carrier level the

is removed from switch 1A5A4-8 and relay 1A5A4K1

detector output is fed to an averaging network on the

deenergizes. The 1A5A4B1 motor input switches from +

receiver/exciter sideband generator board.

12 V to ground through normally closed contacts, 1 and

f. Level Detector. A forward power level and a

9, of 1A5A4K1. This quickly stops the motor and

prevents excessive overshoot.

Diode 1A5A4CR1

reflected power level (VSWR) are the two level detector

prevents motor back emf from keeping 1A5A4K1

outputs.

The forward power level is obtained by

energized. With the motor stopped, all wafer switches

sampling the signal at the antenna connector of the filter

are set to provide the correct filtering for the selected

module. The signal level is dropped by a voltage

band. A filter, capacitors 1A5A4C1, 1A5A4C2 and

divider 1A5A4R1 and 1A5A4R2), and developed by

inductor 1A5A4L1, prevents noise on the motor input

detector 1A5A4CR5.

A filter network (1A5A4C3,

line.

1A5A4R3 and 1A5A4C4) then smoothes the signal for

c. Receiver Protector. Diodes 1A5A4CR18 and

use by the front panel power monitor. The reflected

power level is used to protect the RF power amplifier.

1A5A4CR19 form a shunt power limiter to protect the

The level of reflected power (VSWR) is derived

receiver front end from excessive power input.

inductively (1A5A4T1 and 1A5A4R20) from the signal to

d. Voltage ALC Detector. The ALC (Automatic

the antenna connector on the filter module. The VSWR

Level Control) detector is the sensing circuit for the ALC

is developed by diode 1A5A4CR16 and filter network

circuitry that limits the peak power output to 100 watts.

1A5A4C22, 1A5A4L4 and 1A5A4C23. If the VSWR is

It provides an output reference voltage to the

less than 1.7 to 1 no output (VSWR ALC) is generated.

receiver/exciter for use in the IF stages for output level

g. Keyline. The filter module also contains some of

control. The voltage ALC detector consists of a voltage

the components necessary for transmit keying. Refer to

divider (1A5A4R25 and 1A5A4R26) and RF detector

paragraph 4-1.

(1A5A4CR17), and emitter followers 1A5A4Q2 and

1A5A4Q3. Capacitor 1A5A4C28 filters out any audio

2-11. Antenna Coupler Control Unit 1A2 Detailed

modulation and variable capacitor 1A5A4C24 tunes the

Functional Operation (Fig. 2-4).

circuit for best performance over the transceiver

This unit contains the controls and indicators necessary

frequency range.

for the operator to check, select and monitor antenna

e. ACC Detector. The ACC (Automatic Carrier

tuning. Meter 1A2M1 indicates either reflected or

Control) detector provides a carrier sampling to the ACC

forward power as selected by REFL FWD POWER

circuitry for control of AM power output. The ACC

MONITOR switch 1A2S1. The TUNE START switch

detector derives its output by sampling the signal at the

initiates a coupler tune cycle when depressed if the

antenna connector of the filter module. A voltage

radio set has been set to CPLR TUNE KW. The

divider (1A5A4R4 and 1A5A4R5), a rectifier (1A5A4CR6

COUPLER STATUS indicators provide Antenna Coupler

and 1A5A4CR12), and a filter network (1A5A4C5,

operating condition indications.

Section III. ANTENNA COUPLER CU-2229/URC-92 FUNCTIONAL OPERATION

2-12. Simplified Overall Operation

NOTE

Any time the red FAULT light

The CU-2229/URC-92 antenna coupler is located near

illuminates, it is an indication that

the antenna base and provides automatic antenna

the antenna coupler should be tuned

tuning. Operation is controlled by the antenna coupler

control mounted in the front panel of the RT1277/URC-

In a tune cycle, a demodulated RF is supplied to phase

92 transceiver. Automatic tuning is accomplished by a

and amplitude detectors. These detectors generate

variable inductor and a variable capacitor. Auxiliary,

error signals proportionate to the impedance and phase

fixed value, capacitive circuits are also switched in and

differences of the RF line. The error signals are

out as necessary by relays. When automatic tuning is

differentiated and amplified to drive the DC motors that

initiated at the control unit, a tuning cycle begins The

control 2C1 and 2L4.

green READY light, on the control, illuminates when the

cycle is complete.

2-15