Receiver-Transmitter RT-1277/URC-92 Adjustments.

TM 11-5820-873-34

L8. Repeat as necessary to obtain maximum output as

4-18.

Receiver-Transmitter RT-1277/URC-92

indicated by the RF voltmeter.

Adjustments.

(d) Remove resistive pad connected between

The following adjustments are not intended as a means of

L10 and ground. Remove jumpers from 1A4A1U8-2 and

circuit card assembly checkout or troubleshooting. If an

1A4A1L7. VTVM (AC) remains connected to 1A4A1-4.

adjustment cannot- be performed, troubleshoot the

Again adjust L10, L9 and L8, as in step (c) above, until

related circuit card assembly using conventional

maximum output is attained. Minimum acceptable output,

troubleshooting methods for repair Refer to the List of

when adjusted, is 85 mV RMS.

Illustrations for required schematic figure numbers

(4) 17 MHz Adjustment (1A4A1).

a. Spectrum Generator 1A4A1 Adjustment.

(a) Connect VTVM (AC) (unterminated) to

(1) Remove receiver-transmitter top cover

1A4A1-6. Connect signal generator as shown in Figure 4-

Remove Synthesizer protective cover Place Spectrum

8. Jumper junction of 1A4A1C56, C61 and R50 to CCA

Generator CCA 1A4A1 on card extender Connect a 50

ground.

ohm dummy load to receiver-transmitter ANT jack.

(2) 20 MHz Adjustment(1A4A1).

(a) Connect oscilloscope probe to 1A4A1-1.

Connect frequency counter to oscilloscope vertical

amplitude output.

NOTE

The following adjustment involves three

interacting components Due to this

interaction, the adjustment of each

component should be repeated until

maximum output is obtained.

(b) Adjust 1A4A1L2, 1A4A1L3 and 1A4A1L4

for maximum output Minimum acceptable output is 300

mV peak-to-peak at a frequency of 20 MHz 20 Hz.

(3) 21 Mhz Adjustment.

(a) Connect VTVM (AC) (unterminated) to

Figure 4-8. 17MHz Adjustment Setup (1A4A1)

1A4A1-4. Connect signal generator as shown in Figure 4-

NOTE

The following adjustment involves two

(b) Jumper 1A4A1U8-2 to CCA ground.

interacting components.

Due to this

Jumper across 1A4A1L7 Set signal generator for 250 mV

interaction, the adjustment of each

RMS.

component should be repeated until

NOTE

maximum output is obtained.

The following adjustment involves three

(b) Adjust 1A4A1L16 and 1A4A1L17 for

interacting components.

Due to this

maximum output.

interaction, the adjustment of each

component should be repeated until

junction.

Remove resistive pad connected between

maximum output is obtained.

1A4A1Q6 and ground VTVM remains connected to

1A4A1-6.

(d) Adjust 1A4A1L14 for maximum output

Again adjust L16 and L17 for maximum output. Minimum

acceptable output, when adjusted, is 90 mV RMS.

(5) Remove card extender and reinstall Spectrum

Generator CCA 1A4A1 Reinstall Synthesizer protective

cover Reinstall receiver-transmitter top cover. Remove

dummy load.

b. Low Digit Generator 1A4A2 Adjustment.

(1) Remove receiver-transmitter top cover.

Remove Synthesizer protective cover. Place Low Digit

Generator CCA 1A4A2 on card extender. Connect a 50

ohm dummy load to receiver-transmitter ANT jack.

(2) VCO Adjustment (1A4A2)

Figure 4-7. 21 MHz Adjustment Setup (1A4A1)

for maximum output First adjust L10, then L9, and then

4-39