Motorola R-2400 Operator's Manual page 41

t(mlts 25fiI{s 3{III{z
FIGURE
s.9_AUDIO
FREQUENCY RESPONSE
5.1.1
.0
TRANSMITTER AUDIO DISTORTION
1. Before starting this test, adjust the
transmitter's
IDC to
specification.
2.
Connect
the
service
monitor to the transmitter,
as
shown
in
figure 5.8.
Observe
caution on page
5-5.
3. Turn off
the
modulation. Disable PL or DPL.
Set
"Function"
to "Pwr Mon" (or "Pwr Mon/Anlzr
ont').
4.
Key the
transmitter and adjust the
"l
KHzLvL" con-
trol for
6090
of
full-rated transmitter deviation on
the
left
LCD.
5.
Select
"Dist" on
the
left LCD.
Read
transmitter slo
distortion from the display. Unkey the transmitter.
5.1.2.0 TRANSMITTER AUDIO FREQUENCY
RESPONSE
l.
As
shown
in
Figure
5.7
, connect
the
service
moni-
tor's "RF
InlOut" port to the transmitter's RF out-
put
and the "Yert/Sinad/Dist" input jack
to
the
"Mod Out" jack
through a BNC tee connected to
the transmitter's microphone audio input.
Disable
PL
and
DPL.
2.
Select
6(DVM"
in
the
left LCD
and
set
the
source
switch
to "AC".
Set "Function"
to
"Pwr
Mon",
"FM",
attenuator
to
-40
dB
modulation to "Cont"
and "Tone
A".
Enter the transmitter
frequency.
Turn
off
the
"l
KHzLvl"
and
"Ext Lvl".
When
us-
ing an
R-2400,
the
"Function" switch may
be set
to
"Pwr Mon/Anlzr On"
to
observe
the
occupied
bandwidth
of
the modulated carrier. Set
"Disp" to
.01
MHz/Div.
3.
Enter the required Tone
A
frequency.
4.
Set
"Function" to "Pwr Mon" (or "Pwr Mon/ Anlzr
On").
Key the
transmitter and adjust "Code Synth
Lvl" to provide
3090
of rated transmitter deviation.
5. Note both the
transmitter
MIC audio input
level
and the test frequetrcy,
for
later
use.
6.
Repeat the above
procedure, adjusting "Code
Synth
Lvl" to
maintain
30s/o
of
rated deviation,
for
each
modulation frequency to
be tested.
Plot the
data
points obtained
above
in dB relative to
the
I
KHz level and compare with the transmitter's
specifications.
EIA
RS-1528
specifies
that
a trans-
mitter's frequency
response be
within
+
I
dB or -3
dB
of a
+ 6
dB
per octave pre-emphasis from
300
to
3000
Hz (6 dB per
octave
roll-off
allowed between
2500
and
3000
Hz).
Refer
to
figure
5
.9.
FIGURE
5.10-AM
MODULATION TEST SETUP
5.13.0 AM MODULATION
TEST
Connect
the
service
monitor's "RF
InlOut" to
the
output
connector
of
the transmitter under test,
as
shown
in figure
5.10.
Set
"Function" to "Pwr Mon",
('AM".
Observe
caution
in
basic transmitter
tests
section.
Connect the
service
monitor's
"Mod Out" connector
to
"Yert/Sinad/Dist" and
to
the transmitter's mi-
crophone
input
using a
BNC
tee
connector.
Set
left LCD to "DVM" and the
('AC"
voltmeter
function.
4. Adjust the
"l
KHz
Lvl"
control
to
provide
the
proper input
signal level
to
the
transmitter. Refer to
the transmitter's service
manual
to obtain
the value
for
this
level.
5.
Key the transmitter. Read
9o
AM
on the
left LCD
display.
+9.5
G
7.
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2.
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5-7