TB 9-6625-2137-24
CALIBRATION PROCESS
6. Preliminary Instructions
a. The instructions outlined in paragraphs 6 and 7 are preparatory to the calibration
process. Personnel should become familiar with the entire bulletin before beginning the
calibration.
b. Items of equipment used in this procedure are referenced within the text by common
name as listed in table 2.
c. Unless otherwise specified, verify the result of each test, and whenever the test
requirement is not met, take corrective action before continuing with the calibration.
Adjustments required to calibrate the TI are included in this procedure. Additional
maintenance information is contained in the manufacturer's manual for this TI.
d. Unless otherwise specified, all controls and control settings refer to the TI.
7. Equipment Setup
HIGH VOLTAGE is used or exposed DEATH ON CONTACT
during the performance of this calibration may result if
personnel fail to observe safety precautions.
REDUCE
OUTPUT(S) to minimum after each step within the
performance check where applicable.
NOTE
The oxidation of the battery mounted on circuit board A80 is
causing the traces to corrode; in some cases the corrosion
extends down into the connector. Before calibrating the
AN/USM-490, the circuit board A80 should be removed and
thoroughly cleaned. It may be necessary to replace the battery.
a. Remove protective cover only as required for access to adjustments or test points.
Replace cover after completing the adjustments.
b. Connect TI to a 115 V ac source.
c. Energize TI and allow at least 20 minutes for warm-up and stabilization.
d. After warm-up, verify indicators listed in (1) through (5) below are on:
(1) [AUTO CAL].
(2) MEASUREMENT/ENTRY RANGE [10 dB]; FULL SCALE [AUTO]; and
UNIT [dBm].
(3) FREQUENCY/ENTRY ENTRY FREQUENCY SSB CHANNEL [CARRIER];
CHANNEL [ ], and CNTR FREQ 1000.0000 kHz.
1150 pF].
(4) MEASUREMENT MODE [LO DIST] and TERMINATION [10 k
(5) BANDWIDTH [3100 Hz].
