RECEIVER AUDIO RESPONSE TEST (NORMAL MODE)

TM 11-5820-401-34-3/0967-LP-.432-3060

5-7.

RECEIVER AUDIO DISTORTION TEST. (CONT)

NOTE

To produce a display on the AN/USM-207, the AN/URM-103 rf level must be increased

by turning the LO RF UV control clockwise. When the display appears, readjust the

AN/URM-103 RF TUNING control until the AN/USM-207 indicates 64.00 MHz, and reset

the LO RF UV control to 20v.

Disconnect T-connector from AN/USM-207.

Adjust R-442/VRC VOLUME control for 17-volt indication on TS-723(*)/U meter.

Disconnect TS-723(*)/U METER leads from Test Cable No. 1 terminals.

Connect TS-723(*)/U AF INPUT lead B to Test Cable No. 1 terminal F; connect lead A to

terminal A. (See test setup diagram

Turn TS-723(')KI FUNCTION switch to SET LEVEL.

Set TS-723(*)/U METER RANGE to 100 percent.

Adjust TS-723(*)/U signal INPUT control for full scale meter deflection.

10.

Turn TS-723(*)/U FUNCTION switch to DISTORTION.

11.

Adjust TS-723(*)/U FREQUENCY and BALANCE controls for minimum meter indication,

STANDARD. TS-723(*)/U meter should indicate less than 8 percent.

12. If TS-723(*)/U meter indicates 8 percent or greater, see troubleshooting chart 5-4.

5-8.

RECEIVER AUDIO RESPONSE TEST (NORMAL MODE)

PURPOSE. This test checks the R-442/VRC A5000 tray circuits for a flat response to modulating

frequencies at and below 3 kHz. Receiver circuits are said to have a flat response if their gain remains

nearly constant over a specified bandwidth. Frequencies not falling within this limited range receive

little or no gain. The ability of the R-442/VRC to detect and respond flatly to the desired voice

frequencies is verified by injecting 1 kHz, 500 Hz, and 3 kHz into its ANTENNA port and ensuring that

the power measured at the MUTED audio output (pin F) of Test Cable No. 1 falls within the required

range.

TEST EQUIPMENT AND MATERIALS

Power Supply PP-1104(*)/G

Adapters (two) UG-274 B/U

(T-Connector) and UG-514

Frequency Counter AN/USM-207

Signal Generator AN/URM-127

Matching Unit CN-901/U

Signal Generator AN/URM-103

Rf Cables (two) RG-58/U

Ac Voltmeter ME-30(*)/U

Resistor, 600-ohm 5%, 2-watt

Test Cable No. 1

NOTE

The 600-ohm resistor provides an impedance matching load for the audio transformer.

The resistor is used in place of Loudspeaker LS-454/U, which would issue a loud,

distracting tone when the R-442/VRC VOLUME control is adjusted during the test. If no

600-ohm resistor is available, however, the loudspeaker must be connected. (See test

setup diagram

, page 5-22.)

5-21