TB 9-6625-1914-24
Figure 10. Local oscillator stability.
(4) Multiply horizontal displacement noted in (3) above by the setting of the SCAN
WIDTH PER DIVISION switch to convert horizontal displacement into Hz.
Example:
(0.2 kHz) x (0.2 div) = 40 Hz
0.2 kHz = setting of SCAN WIDTH PER DIVISION switch
Where:
0.2 div = horizontal displacement from (3) above
(5) Calculate demodulation sensitivity by dividing vertical displacement in divisions
into horizontal displacement in Hz calculated in (4) above.
Example:
40 Hz
= 13.3 Hz/div
3 div
(6) Set SCAN WIDTH (red) switch to ZERO and adjust FREQUENCY FINE
TUNE control for a response level within the calibrated 3-division range (1 division
from top to center horizontal graticule line).
(7) Measure p-p deviation and multiply demodulation sensitivity obtained in (5)
above. The stabilized residual FM calculated must be less than 20 Hz p-p.
Example:
0.5 div p-p signal deviation x 13.3 Hz/div = p-p residual FM
(8) Set BANDWIDTH switch to 1 kHz and SCAN WIDTH (red) switch to PER DIVISION.
(9) Repeat (3) through (5) above to calculate demodulation sensitivity. (A typical
value for demodulation sensitivity with control settings given is 135 Hz/div.)
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