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Chapter 6 - Maintenance
6
.1
General Information
The
Model
EAS
930A
Multi-Module Receiver as shipped from
the
factory is ready for immediate use.
No
calibration is required;
however
, periodic performance checks should
be
made
. This section
discusses those checks and the adjustments
that may be required
to
maintain optimum system
performance.
Performance checks and adjustments described in this section require specific test equipment. The
following is a s
ugge
s
ted
list
of
t
es
t equipment. ·
Test Equipment Required:
1 . Digital multimeter, accurate
to
within ± 1 %
2.
Distortion analyzer
3.
Frequency counter,
up
to 1
GHz
4.
O
sc
illoscope with I
00
MHz
or
better bandwidth
5.
RF
signal generator,
50Q
impedance with 88-108
MHz
FM
, 162 - 165
MH
z
FM
, and
500-1700
kHz
AM
output
6.
2 AM Receiver Performance Checks
The Model
930A
AM
receiver
's
sensitivity and
AGC
range should be checked periodically.
Th
e
following paragraphs discuss the procedures for making these
check
s using the equipme
nt
listed in
Paragraph 5.1 above.
6.
2
.1
AM Receiver Sensitivity Check
To
check the
AM
Receiver sensitivity, proceed as follows:
a.
Connect
an
RF
signal generator to
the
AM
receiv
er
's
RF IN connector (part
of
Figure 3.3-5,
Item
3)
on
the
EAS
930A
rear panel.
b.
Set
the signal generator output frequency
to
540
kHz,
AM
modulation
to
30%. Set the
generator output level to
20
µ V.
c.
Set
the
3-digit
BCD
rotary
DIP
switch (Figure 3.3-3)
to
0.540
MHz, and the
LOCAUDISTANT switch
to
DISTANT.
d.
If
the receiver is configured for hot standby, remove
th
e top cover and place
the
AUTO
SWITCH
in
the
OFF
position. Return it
to
the
ON
po
sition after completing this
te
st.
e.
Connect
an
oscilloscope and distortion analyzer in parallel to
the
AM Receiver's BALANCED
AUDIO OUTPUT terminal block connector at the rear panel.
f.
Tum
on
the modulation.
Ob
se
rve the oscillosco
pe
.
The
audio
wa
veform should still be
pr
es
ent
on
th
e scope.
6-1
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General