Phase Modulation Check - Racal Instruments 9081 Maintenance Manual

5.32
(2)
Connect:
-
(a)
Audio generator
to
FM/^ZSM
EXT
600^
socket
(b)
Modulation meter
to
UUT 500
output
(c)
Millivoltmeter
and frequency counter
to
monitor
the output
of the
audio generator.
(d)
The
distortion
analyser
to
the
AF
output of the
modulation meter.
(3)
Tune
the
UUT
to
520
MHz.
(4)
Apply
the external
audio modulating frequencies as
in
Table
12.
Monitor
the
audio
frequencies with the counter
and
maintain the
audio
level at
1.00V
r.m.s.
on the millivoltmeter.
Check
deviation
on the modulation
meter and
distortion (not
exceeding 4%) on
the
analyser.
TABLE
12
Phase
Modulation
Check
Audio
freq.
Deviation Distortion
400 Hz
4kHz
±5%
-o
VI
1000Hz 10kHz
±
5%
^ 4%
5000Hz
i
50kHz
±5%
1
4%
(5)
Retain the
test
equipment
for
the
next check.
AM
DEPTH
and
DISTORTION
CHECK
5
.
33 Test
Equipment Required
As
in
para.
5.31, except frequency counter.
Modulation
Meter
Item 13 of
Table 5 (9082 only).
5
.
34
Procedure
(1)
Connect
the
test
equipment
as
in
5.32
(2)
but with the audio
generator connected
to
the
AM
EXT 600Q
socket.
9081
&
9082 Vol.2.
5-24