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g.
Note
the
reading
on
the
meter
, then set
the
distortion analyzer to 0
dB
,
and
turn
off
the
modulation.
Read
the
meter.
The
difference in
the
readings with modulation on and with
it
off
should
be
greater
than
20
dB.
h .
Set
the signal
ge
nerator
output
to
540
kHz
and
AM
modulation
to
50%
at
a modulation
frequency
of
1 kHz.
Set
the
output
level
to
10 µ V.
1.
Connect a multimeter to RSSI (Received Signal Strength Indication)
on
the
AM
Receiver
Module
(part
of
Figure
3.3-3).
J.
Slowly increase
the
RF level
of
the
signal generator
to
approximately
30
mV.
The
voltage on
the
multimeter
at
the
RSSI should indicate a
change
from 3 V
to
6 VDC.
6.2.2
AM Receiver AGC Range Check
To
check
the
AM
receiver
AGC
range,
proceed
as follows:
a.
Ensure
the
signal generator is connected to the RF INPUT connector
of
the
AM
Receiver
Module
at
the
930A
rear
panel
,
and
its output frequency is
set
to
540
kHz
with AM
modulation
to
66%
at
a 1
kHz
modulating frequency.
Set
the
output
level to
20
µ V.
b. Connect an oscilloscope to the BALANCED AUDIO OUTPUT tenninal block connector
at
the
rear panel.
c.
Set
the
DISTANT/LOCAL
swi
tch
to
the
LOCAL position, then increase
the
signal
gene
r
ator
level
to
30
mV.
The
1
kHz
sine
wave
on
the
oscilloscope
should
remain
un
distorted.
d.
Repeat
steps
a
and
b
above
for
1000
kHz
and
1600
kHz
input signals.
6.
2.
3
AM
Receiver Audio Output Adjust
To
adjust
the
AM
Receiver
audio
output,
pr
oceed
as
follows:
a.
Connect a
600Q
load
and
the
balanced input terminals
of
a distortion analyzer
to
the
AM
receiver module BALANCED AUDIO OUTPUT terminals block connector
at
the
rear
panel.
b.
Connect
a signal gene
rator
with
an
540
kHz
carrier, modulated
90%
at
1 kHz,
to
the
RF
INPUT
connector
at
the
rear panel.
Set
the
signal
le
vel
to
100
µV
.
c.
While
observing
the
meter on
the
distortion analyzer, adjust
the
AUDIO
OUT
ADJUST
at
the
rear
panel
for
O
dBm.
6.
3 FM Receiver Performance Checks
The
FM receiver's sensitivity
and
AGC
range
shou
ld
be
checked
periodically.
The
following
paragraphs discuss
the
procedures
for
making
these c
he
cks
using
the
equipment listed in
Par
agraph
6.1.
6 . 3
.1
FM Receiver Sensitivity Check
To
check
the
FM receiver sensitivity,
proceed
as
follows:
6-2
a. Connect a signal generator to
the
FM Receiver Module
RF
INPUT connector
at
the
rear panel.
b .
Set
the
signal generator output frequency to
100
MHz,
and
the
frequency deviation for
±25
kHz
at
a 1
kHz
modulating frequency.
Set
the
output
l
eve
l
to
2 µV.
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