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ACCEPTANCE TESTING
7-23
Phase modulation flatness
Test procedure
For this test, the phase modulation figures are calculated from readings taken with the modulation
meter set to FM. No allowances need to be made for the modulation source frequency accuracy
since it is derived from the reference oscillator in the UUT.
(1) Connect the test equipment as shown in
Fig. 7-8
.
(2)
On the UUT set source A to:
[Carr
Freq]
15
[MHz]
[RF
Level]
0
[dB]
[
Φ
M] [
Φ
M Devn]
10
[rad]
[
Φ
M
ON/OFF]
(3)
On the modulation meter, select CAL, FM, 50 Hz
Þ
15 kHz LF filter.
(4)
Measure the deviation on the modulation meter and calculate the phase modulation using the
formula:
Φ
M = FM dev (Hz)
mod
freq
(Hz)
(5) On the UUT set
[
Φ
Mod Freq]
to each of the frequencies shown in
Table 7-35
, measure the
deviation on the modulation meter and calculate the phase modulation for each step using
the formula in (4).
(6)
Using the figure recorded in (4) as a reference, calculate the change in response at each
modulation frequency using the formula:
20log
10
Figure recorded in (5)
Figure recorded in (4)
Check that the results are within the specifications shown in
Table 7-35.
(7)
Repeat (2) to (6) for source B.