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6.
4 NOAA Weather Radio Receiver Performance Checks
The NOAA Weather Radio Receiver
's
sensitivity and AGC range should be checked periodically. The
following paragraphs discuss the procedures for making these checks using the equipment listed in
Paragraph 5.1.
6.4.1
NOAA Weather Radio Receiver Sensitivity Check
To check the
NOAA
Radio Receiver sensitivity, proceed
as
foUows:
a. Connect a signal generator
to
the receiver's
RF
INPUT connector
on
the rear panel.
b.
Set
the
signal generator output to 162.5 MHz,
and
the frequency deviation for ±5 kHz at a
1
kHz
modulation frequency.
Set
the output level
to
2
µV
.
c.
Set the I-digit rotary switch (Figure 3-3) to channel 6 (162.5 MHz).
Set
th
e
LOCAUDISTANT
switch
to
Distant
(DX).
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
NOAA
Radio Receiver
's
BALANCED AUDIO OUTPUT terminal block connector at 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.
Turn
on
the modulation. Observe the oscilloscope.
The
waveform should still
be
present
on
the
sco
pe.
h.
Set
the
signal generator output level to 1 µV.
1.
Connect a multimeter to
TP
1 (RSSI)
on
the front panel.
J. Slowly increase the
RF
level
of
the signal generator
to
approximately l
00
µV.
The
voltage on
the multimeter at
TPl
should indicate a change from
6.0
to 6.5 VDC.
6.4.2
NOAA Weather Radio Receiver
AGC
Range Check
To check
th
e
NOAA
Weather Radio Receiver AGC range, proceed
as
follows:
6-4
a. Ensure that a signal generator is connected
to
the
RF
INPUT
connector
on
the receiver
module at the rear panel.
b.
Using
the
I-digit rotary switch at the front panel, set the receiver
to
the channel 6
(162.5 MHz).
c.
Set
the signal ge
nera
tor
output frequency to 162.5
MHz
and
the frequency deviation for ±5
kHz at a 1 kHz modulation frequency. Set the output level
to
10 µV.
d. Connect an oscilloscope
to
the BALANCED AUDIO
OUTPUT
terminal block
co
nnector at the
rear panel.
e.
Set the LOCAL/DIST
ANT
switch to the LOCAL position, then increase the signal generator
level to I mV.
The
l kHz sine
wave
displayed on the oscilloscope should remain
undistorted.
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