TB 9-6625-2089-24
18. Modulator and Demodulator Accuracy
a. Performance Check
(2) Position controls as listed in paragraph 7 e above.
(3) Observe that two pulses are present and adjust oscilloscope to position
intensified trace over second pulse.
NOTE
If necessary, the 0.1 μs markers on CH2 of oscilloscope may be
used to make the measurements in (4) through (7) below.
(4) Adjust MEASUREMENT DEMOD VID LEVEL control for a pulse amplitude
of 2.0 V as, indicated on oscilloscope CH1 input. Measure pulse width. Pulse width will be
between 0.75 and 0.85 μsec.
(5) Measure risetime at the 1 and 81 percent amplitude points. If risetime is not
between 0.05 to 0.10 μs, perform b (1) below.
(6) Measure falltime using technique of (5) above. If falltime is not between 0.05 to
0.20 μs, perform b (2) below.
(7) Disconnect cable from MAIN RF IN/OUT jack and connect to AUX RF IN/OUT
jack and repeat (3) through (6) above. Pulse rise and falltime will be between 0.05 and 0.20
μs, if not perform b (3) below.
b.
Adjustments
(1) Adjust A16A1R40 (fig. 1) for 0.08 μs (R).
(2) Adjust A16A1R40 (fig. 1) for 0.12 μs (R).
(3) Adjust A16A1R39 (fig. 1) for 0.12 μs (R).
a. Performance Check
(1) Connect power meter to MAIN RF IN/OUT connector.
(2) Position controls as listed in (a) through (d) below:
CHAL MODE SELECT switch to CW.
(a)
SIG GEN FUNCTION switch to FIXED FREQ.
(b)
MAIN ATTEN control to -10 dB.
(c)
AUX ATTEN control to -10 dB.
(d)
(3) Power meter will indicate -10.0 1.0 dBm, if not perform b below. Record power
meter indication.
(4) Set SIG GEN FUNCTION switch to SWP 5 MHz. Power meter will indicate
within 1.0 dBm of value recorded in (3) above.