TM 11-6625-586-45
f. Connect HI-RF terminal of unit under test
7.5 and 12.5 uv. If meter reading is not within
through impedance matching network Z153 to HI
prescribed limits, proceed to step i.
terminal of RX meter.
g. Turn IF MHz switch to 10.00 and repeat
g. Successively, select outputs of 62.5 KUV,
steps d, e, and f.
125 KUV and 250 KUV with RF OUTPUT switch
h. Turn IF MHz switch to 11.5 and repeat
and repeat step d above.
steps d, e, and f.
should be 50 10 ohms +j 0 15 ohms.
work Z107.
5-8. External Modulation Input Impedance
a. S e t O P E R A T E - O F F - S T A N D B Y t o O P -
tions listed below.
ERATE.
Position
Switch
b. Turn FUNCTION switch to EXT MOD.
FUNCTION
IF
c. Connect the EXT MOD terminal of the unit
IF MHZ
4.300
under test to impedance bridge.
IF OUTPUT
1.0 VOLT
d. Measure the impedance at the EXT MOD
k. Adjust IF METER CAL control R69 for
terminals. It should be between 510 and 690 ohms.
1.0 indication on IF UV RF SET TO LINE
meter.
5-9. IF Output Impedance
a. Set OPERATE-OFF-STANDBY switch to
5-11. IF Spurious Outputs
OFF.
a. Connect the unit under test and the test
b. Set FUNCTION switch to MOD OFF and
equipment as shown in figure 5-4.
IF OUTPUT switch to 10UV.
b. S e t O P E R A T E - O F F - S T A N D B Y t o O P -
c. Connect the unit under test and the test
ERATE and turn FUNCTION switch to IF and
equipment as shown in figure 52.
IF OUTPUT switch to 1.0 VOLT.
d. At IF frequencies of 4.300 MHz and 11.50
c. Measure the hamonic distortion for each
MHz, measure the IF output impedance at each
position of the IF MHZ switch: 4.300, 5.600,
position of IF OUTPUT switch except OFF and
5.625, 10.00 and 11.50. The harmonic distortion
1.0 VOLT. The IF output impedance should be:
should be 10 percent for each switch position.
25 5, ohms + j 0 10 ohms.
5-12. Internal Modulation
5-10. IF Output Level
a. Connect electronic counter AN/USM207 to
a. Set OPERATE-OFF-STANDBY switch to
INT MOD OUT jack.
OPERATE.
b. T u r n F U N C T I O N s w i t c h t o I F , I F M H z
b. Set OPERATE-OFF-STANDBY switch to
switch to 4.300 and IF OUTPUT switch to 1.0
OPERATE.
VOLT.
c. Turn RF OUTPUT switch to 250 KUV.
d. Turn FUNCTION switch to 1000 Hz.
output jack through impedance matching
e. Adjust LO-HI RF SET TO LINE control
network Z107.
for red line indication on IF UV RF SET TO
d. With IF UV control, maintain 1.0 indica-
LINE meter.
tion on IF UV RF SET TO LINE meter and
f. Turn FUNCTION switch successively to 150
observe multimeter reading at the 1.0 VOLT,
Hz, 400 Hz and 1000 Hz. The electronic counter
10 KUV and 1 KUV positions of IF OUTPUT
should indicate within the specified limits given
switch.
The meter read-
in table 5-4 for each modulating frequency. If
ing should be within 25 percent of selected
any frequency is off, proceed to step i.
range. If any meter reading is not within pre-
scribed limits, proceed to step i.
Table 5.4 Modulating Frequency Accuracy
e. To measure the IF output when the IF OUT-
PUT switch is in the 100 UV and 0-10UV posi-
Frequency counter reading (Hz)
tions, connect the test setup (fig. 5-3).
FUNCTION switch
setting
Minimum
Maximum
149
151
150 Hz
erence and observe the meter reading on the
405
395
400 Hz
receiver. The meter reading should be between
1050
950
1000 Hz
Change 1 5-7
