TM 11-6625-586-45
serving the electronic counter when an audible
f. Turn the RF OUTPUT switch to 250 KUV
beat note is heard.
and repeat step c. At each frequency, the RF
f. Disconnect the speaker and connect the out-
voltmeter should indicate between 187.5 and 312.5
put power meter and electronic counter in its
kuv.
place.
g. Turn the RF OUTPUT switch to 500 KUV
g. Set the output power meter for 12 ohms
and repeat step c. At each frequency, the RF
impedance.
voltmeter should indicate between 375 and 625
h. At the following frequencies: 22, 24, 28, 34,
kuv.
42, 51 and 77 MHz, vary the RF TUNING con-
6-12. Internal Modulation
trol to vary the beat note frequency from 500
Hz to 2000 Hz as indicated on the electronic coun-
a. Connect unit under test and test equipment
ter. The power output at the 500 Hz and 2000
as shown in figure
Hz points should be greater than 3 milliwatts.
b. Turn RF OUTPUT switch to 250 KUV.
i. Reconnect the speaker removed in step f.
c. Turn FUNCTION switch to 1000 Hz.
d. Adjust LO-HI RF SET TO LINE control
Table 61. Oscillator Beat Note Power and Spurious Beat
for red line indication on IF UV RF SET TO
Notes.
LINE meter.
Specified limits for hearing
Band
e. Turn FUNCTION switch successively to
beat note (Hz)
150 Hz, 400 Hz and 1000 Hz. The electronic
A
18
675
19
713
counter should indicate within the specified lim-
25
938
its given in table 6-2 for each modulating fre-
25
957
quency.
B
26
975
27
1013
Table 6-2. Modulating Frequency Accuracy.
37
1388
Frequency counter reading (Hz)
FUNCTION switch
38
1425
Maximum
Minimum
C
37
1388
151
149
150 Hz
38
1425
405
4 0 0 Hz
395
53
1988
1050
1000 Hz
950
54
2025
D
54
2025
2063
55
and with the specified switch settings, check that
2963
79
the deviation and distortion readings are within
3000
80
limits.
6-11. High RF Output Voltage Range and
Accuracy
6-13. External Modulation
a. Connect the unit under test and the test
a. Turn FUNCTION switch to EXT MOD and
equipment as shown in figure 6-2.
RF OUTPUT switch to 250 KUV.
b. Turn RF OUTPUT switch to 62.5 KUV.
b. Adjust LO-HI RF SET TO LINE control
for red line indication on IF UV RF SET TO
c. Observe the RF voltmeter reading at the
LINE meter.
following frequencies: band A 18 and 26 MHz,
band B 26 and 37 MHz, band C 38 and 54 MHz,
MOD terminals of the unit under test.
and band D 54 and 80 MHz.
d. At each frequency, the RF voltmeter should
terminals. It should be between 510 and 690
indicate between 47 and 78 kuv.
ohms.
e. Turn RF OUTPUT switch to 125 KUV and
e. Connect the unit under test and the test
repeat step c. At each frequency, the RF volt-
equipment as shown in figure 6-3.
meter should indicate between 94 and 156 kuv.
Figiure 6.Oscillator beat not power and spurious beat note, test connections.
6-2
