Am Frequency Response Check - Racal Instruments 9081 Maintenance Manual

AM
FREQUENCY
RESPONSE
CHECK
5.37
Test
Equipment
Required
Page 5-2
Table 5
As
in
the
preceding
test,
plus:-
Digital
Multimeter Item
1
Power Meter
Item 11
5.38 Procedure
(1)
Transfer the
audio generator and monitor
millivoltmeter
to
the
AM
EXT
600Q
socket.
The modulation meter remains
connected
to
the
UUT 50D
output
.
(2)
On
the
UUT
set
the
F/V\/QM switch
to
OFF
and
the
AM
switch
to
EXT
.
Adjust
OUTPUT
LEVEL
controls for
3dBm
level
.
(3)
With
the
UUT
tuned
to
520MHz,
refer to
Table 15.
Apply
the
external
audio
frequencies,
monitored
at
800mV, and
verify the
specified
modulation depth on
the
modulation meter.
TABLE
15
AM
Frequency
Response
Check
Audio
freq.
Millivoltmeter
reading
Modulation
meter reading
20
Hz
800
mV 80%
±
3%
100
kHz 800
mV
80%
±
3%
1
kHz
800
mV
80%
±
3%
10
kHz 800
mV
80%
±
3%
30
kHz 800
mV
80%
±
3%
(
20
kHz
for
9082)
(4)
Set the external
audio generator frequency
to
1
kHz
and
adjust
the
audio
level
until
the
modulation meter
reads
50%AM.
Note
the reading
on
the
monitor millivoltmeter
at the
AM
EXT
input socket.
(5)
Disconnect
the
modulation meter and connect
the
Power Meter
in
its
place.
(6)
Monitor
the
d.c. output voltage of
the
power
meter
using the digital
multimeter
(d.v.m.)
(7)
Adjust the
UUT OUTPUT
LEVEL
controls
to
give a reading of
1
.000V
on
the
d.v.m.
9081
&
9082 Vol.2.
5-27