TB 9-6625-2171-35
(3)
Press VOR 30VAR and 30REF pushbuttons and measure distortion. Adjust
square wave on oscilloscope (R).
(4)
Disconnect equipment setup and reconnect audio analyzer to measuring
receiver modulation output. Measure distortion. If distortion is still high, adjust A5L5 and
A5L6 (fig. 4) for minimum distortion (R).
NOTE
If A5L5 and A5L6 (fig. 4) were adjusted, recheck paragraph
15a(4) above VOR RF level.
a. Performance Check
(1)
Connect oscilloscope CH1 to TI A6J12 (fig. 3).
(2)
Adjust oscilloscope controls for an 8 division sinewave display presentation at
vertical setting of 200 mV/div, uncal, and horizontal setting of 100 s/div.
(3)
Center sinewave on oscilloscope crt and adjust trigger level control to start
sinewave at horizontal graticule centerline.
Utilizing a delay time of 10 s/div, expand the fifth cycle portion of the TI
(4)
signal as indicated in figure 5. Measure and verify the width of the jitter. Verify the
deviation of the expanded jitter display, as shown in figure 6, is equal to 48.5 s +3 s.
NOTE
The width of the jitter is proportional to the 9960 Hz FM
signal. A 9960 Hz signal deviating 480 Hz varies between
9480 and 10,440 Hz. The period of 10,440 Hz is 95.785 s and
the time for five cycles is 478.925 s. The period of 9480 Hz is
105.485 s and the time for five cycles is 527.425 s. The
difference between them (527.425 s minus 478.925 s) is 48.5
s. For a tolerance of 480 30 Hz deviation, the width of the
jitter must be 48.5 3 s.
