RECEIVER AUDIO RESPONSE TEST (NORMAL MODE).

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

3-7. 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 20 v.

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 MK-1978/VRC jacks.

Connect TS-723(*)/UAF INPUT lead B to MK-1978/VRC SPKR jack; connect lead A to GND

jack. (See test setup diagram

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

Set TS-723(*)/U METER RANGE switch 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 (distortion),

12. If TS-723(*)/U meter indicates 8 percent or above, see troubleshooting chart 3-4.

3-8. 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 insuring that

the power measured at the SPKR jack of the MK-1978/VRC falls within the required range.

TEST EQUIPMENT AND MATERIALS

Power Supply PP-1104(*)/G

Adapters (two) UG-274 B/U (l-

Frequency Counter AN/USM-207

Connector) and UG-514

Matching Unit CN-901/U

Signal Generator AN/URM-127

Rf Cables (three) RG-58/U

Signal Generator AN/URM-103

Ac Voltmeter ME-30(*)/U

Maintenance Kit MK-1978/VRC

3-21