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c.
Set
the
3-digit
BCD
rotary
DIP
switch (Figure 3.3.2)
to
10-0-0
(100
MHz).
Set
the
DISTANT/LOCAL switch
to
DISTANT.
d.
If the receiver is configured for
hot
standby, remove the
top
cover
and
place
the
AUTO
SWITCH
in
the
OFF
position. Return
it
to the
ON
position after completing this test.
e. Connect
an
oscilloscope
and
distortion analyzer in parallel
to
the
FM
Receiver's BALANCED
AUDIO
OUTP
UT
terminal block connector on the rear panel.
f.
Note
the
reading
on
the
meter
, then set
the
distortion analyzer
to
O
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.
g.
Tum
on
the
modulation. Observe the oscilloscope.
The
waveform
should
still
be
present on
the scope.
h.
Set
the signal generator output level
to
1 µ V.
i. Connect a multimeter to
TPl
(RSSI)
on
the front panel.
j.
Slowly increase the
RF
level
of
the signal generator
to
approximately
100
µ V.
The
voltage on
the multimeter
at
RSSI should indicate a change from 1
to
3
VDC.
6.3.2
FM Receiver AGC Range Check
To
check the
Receiver
AGC
range, proceed
as
follows:
a.
Ensure that a signal generator is connected to the
RF
INPUT connector
on
the
FM
Receiver
board
rear panel.
b.
Using
the
3-digit
BCD
rotary
DIP
switch
on
the front panel, set
the
FM
Receiver
to
100MHz.
c.
Set
the
signal generator output frequency to 100
MHz
,
and
the frequency deviation
to
±75
kHz
at
a 1
kHz
modulating frequency.
Set
the
output level
to
20
µV.
d.
Connect
an
oscilloscope
to
the
FM
Receiver's BALANCED
AUD
IO OUTPUT terminal block
connector
on
the
rear
panel.
e.
Set
the DISTANT/LOCAL switch
to
the LOCAL position, then increase
the
signal generator
level
to
10
mV.
The
1
kHz
sine
wave
on
the
oscilloscope
should
remain undistorted.
6.
3.
3 FM Receiver Audio Output Adjustment
To
adjust the
FM
Receiver
audio
output, proceed as follows:
a.
Connect
a
600Q
load
and
the balanced output
of
a distortion analyzer
to
the BALANCED
AUDIO OUTPUT
terminal
block
connector
on
the rear panel.
b.
Connect a signal generator with an 88
MHz
carrier, modulated
at
1
kHz
with
±75
kHz
deviation,
to
the
RF INPUT connector
on
the rear panel.
Set
the signal level
to
100 µ V.
c.
While
observing
the
meter
on
the
distortion analyzer, adjust
R4
on
the
rear panel for O dBm.
6-3
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