MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
Chapter 6: Additional Radio System Tests
Page 62
Spurious Signals over the Air
A spurious signal test can be performed by keying up the transmitter over the air and observing the
spectrum using a Spectrum Analyzer with an antenna on the input port as shown in Figure 6-5.
On the Spectrum Analyzer, attenuate the incoming RF signal so that the RF carrier does not extend
beyond the range of the display on the Spectrum Analyzer (this will overdrive the receiver of the analyzer
causing erroneous spurs to be shown in the spectrum).
Look at the spectrum and ensure there are no large spurs being generated by the radio system.
Figure 6-5: Spurious Signals over the Air Test
TRANSMITTER
CNTL
BUS
MIC
RF OUT
A D
ANALOG
DIGITAL
NORM
OFF
KEY TX
MIC MODE
REF
IN
USB
FREQUENCY (MHz)
MADE IN CANADA
MODEL # CODE
RECEIVER
NORM
SQ. DISABLE
OFF
CNTL
BUS
A D
RF N
I
REF
IN
USB
FREQUENCY (MHz)
MADE IN CANADA
MODEL # CODE
VOL
SYSTEM REGULATOR
METER
+
-
MADE IN CANADA
ON
OFF
SPKR
INT
EXT
EXT
SPKR
OFF
POWER
ON
2
1
5
4
3
6
7
8
11
10
9
FUNCTION
12
REPEATER
CONTROL
RX B
TX B
RX A
TX A
PULL DOWN
TO REMOVE
9
5
3
7
11
15
9
13
3
7
11
15
SWITCH A
SWITCH B
Radio System Transmitting Over the Air
Spectrum Analyzer
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