ZETRON Viavi CX300 Operating manual

i
Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
Appendix H:
Viavi CX300 Tests
MAINTENANCE GUIDE
www.zetron.com
™

Contents
ii
Appendix H: Viavi CX300 Tests | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
Appendix H: Viavi CX300 Tests
MT-4E TESTING WITH THE CX300 BY VIAVI � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �01
GENERAL SET-UP AND CONNECTIONS � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �02
Uploading Zetron Configurations to the CX300 � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 02
Radio Service Software (RSS) � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 03
Control Cards � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 03
Adapters, Cables and Extender Cards � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 03
Zetron MT-4E Radio System Test Sheet � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 03
Turning OFF the MT-4E Receiver and Transmitter Modules � � � � � � � � � � � � � � � � � � � � � � 04
Audio Connections � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 05
SYSTEM REGULATOR TESTING � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �06
System Voltage Testing � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 06
RECEIVER TESTING � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �07
Receiver Analog Testing � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 07
Receiver Digital / BER Testing � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 11
Receiver RF Preselector Alignment and Tuning � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 13
Receiver Reference Oscillator Adjustment � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 15
TRANSMITTER TESTING � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �18
Transmitter Analog Testing � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 18
Transmitter CTCSS Testing � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 24
Transmitter Digital Testing � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 27
SYSTEM TESTING � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �30
Duplex Analog Testing � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 30
Duplex Digital Testing � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 33

01
Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
Appendix H: Viavi CX300 Tests
MT-4E TESTING WITH THE CX300 BY VIAVI
This Chapter contains instructions for Tuning, Testing, Maintaining and Servicing MT-4E Analog and P25 Digital
Radio Systems with the CX300 ComXpert by Viavi.
This Chapter is intended as an aid to configuring and testing Zetron MT-4E radios using the CX300. Neither Zetron
or Viavi Solutions assume responsibility for damage caused to either unit as a result of misinterpretation or misuse
of this procedure. Zetron manufactured products are warranted against defective materials and workmanship.
This warranty does not extend to damage due to misuse, neglect, accident, improper configuration or
installation. Zetron and Viavi shall be released from all obligations under its respective warranty in the event the
Products are subject to misuse, neglect, alteration, accident, improper installation or testing, or if unauthorized
repairs are performed by the customer or others.
These procedures can be modified, changed and altered at any time to better suit your specific needs and
requirements. Refer to Zetron Instruction Manuals for complete radio system specifi cations.

02
Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
GENERAL SET-UP AND CONNECTIONS
Uploading Zetron Configurations to the CX300
The CX300 allows for configuration files to be saved and recalled on the test set. These configuration files are
uploaded to the test set from a USB flash drive.
The CX300 configuration files are available from the Zetron website at www.zetron.com. The file can be
downloaded, then unzipped and copied onto a USB flash drive.
To upload a file from a USB flash drive, insert the USB flash drive into one of the USB ports and select the Home
button, then Files. Copy the Zetron folder from the USB flash drive to the /Disk/CX300/Internal folder. To recall
setups while in the CX300 ComXpert test screen, go to the right hand side of the screen and select the file icon,
then navigate to the /Internal/Zetron folder, select the recall file then select LOAD.
Please note that some of the setups that are recalled are generic and may need to be changed for your
specific receiver and transmitter settings.
The generic saved setups are as follows:
Audio = 1000 Hz @ 1.5 KHz deviation (for wideband set this to 3.0 KHz deviation)
CTCSS = 100.0 Hz @ 0.35 KHz deviation (for wideband set this to 0.5 KHz deviation)
NAC = 293
TGID = 1

03
Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
Radio Service Software (RSS)
Start the RSS program on the computer and ensure you are connected to the receiver or transmitter via the
type A to 5 pin mini-type B USB cable. Read the transmitter or receiver programming and familiarize yourself
with the settings (RF frequency, wide / narrowband, digital / analog, CTCSS / NAC, etc.).
Control Cards
Some Zetron MT-4E radio systems may have an AC-3E Audio Control Card or CI-BC-4E Base Control Card for use
in the radio system. The Control Cards connect to the receiver and transmitter balanced audio lines with an
unbalanced load, which could cause some measurements to be in error. If the radio system includes an AC-
3E Audio Control Card or CI-BC-4E Base Control Card, remove the control card from the rack for the individual
receiver and transmitter tests unless otherwise noted.
Adapters, Cables and Extender Cards
Various adapters, cables and extender cards are required for the different radio tests. Extender cards and
adapters are available from Zetron Communications. The receiver reference oscillator and RF preselector filter
tests require an SMB - BNC adapter and a small SMB - SMB cable is required for the reference oscillator test as
well. The SMB adapters and cables are included in the A-TK-04 Tool Kit.
Zetron MT-4E Radio System Test Sheet
A Zetron MT-4E Radio System Test Sheet is included in Chapter 7 of the Maintenance Guide. It is recommended
that this test sheet be filled out each time the radio system is tested. If two or more pairs of transceivers are
tested, use a second test sheet to record the results. The test sheet will record settings for a single Tx and Rx
frequency, however other frequencies can be tested and recorded if desired.

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Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
Turning OFF the MT-4E Receiver and Transmitter Modules
Turning the switch on the front panel of the MT-4E receiver or transmitter modules to the OFF position can cause
unwanted effects on other MT-4E receiver and transmitter modules.
When the MT-4E receiver and transmitter are connected directly together with the LVDS serial data RJ45 cable,
turning the MT-4E transmitter front panel switch to the OFF position will cause the MT-4E receiver module to turn
off. The MT-4E receiver modules A and D LEDs on the front panel will blink on and off when this occurs. Turning
the MT-4E receiver modules front panel switch to the OFF position will not cause any adverse effects on the
MT-4E transmitter. When turning the MT-4E receiver modules front panel switch from the OFF to NORM position
(or vice versa), it will cause the MT-4E transmitter to reboot. Remove the RJ45 cable to stop this interaction from
occurring. When connecting the LVDS serial data RJ45 cables to the CI-RC-4L repeater control card or CI-RC-
4M-G2 multiple link controller, the MT-4E receiver and transmitter modules are isolated from each other and the
modules can be turned on or off independently of each other.
When the MT-4E receiver and transmitter channel and bank select lines are connected together in parallel,
turning the MT-4E receiver or transmitter front panel switch to the OFF position will cause the channel and bank
select lines to be grounded. This will cause the other MT-4E module to operate on Bank B, Channel 1 regardless
of how the channel and bank select lines are set. If the bank select lines are not connected in parallel, only the
channel will be affected. The channel select lines are independent of the LVDS serial data RJ45 cables (the
cables will have no impact on the channel select).
When the MT-4E receiver and transmitter are connected to the antenna relay in the System Regulator module,
turning the MT-4E transmitter front panel switch to the OFF position will cause the MT-4E transmitter PTT OUT
line to be grounded, activating the antenna relay and causing it to be switched so that the transmitter is
connected to the antenna. This makes it impossible to test the MT-4E receiver through the antenna relay when
the MT-4E transmitter is turned off.
When performing maintenance on the Zetron MT-4E radio system it is best to simply remove the MT-4E receiver
or transmitter, that is not being tested, from the subrack and disconnect all RJ45 cables, rather than turning the
front panel switch to the OFF position. All Zetron modules are hot swappable. There is no need to disconnect
the power supply when inserting or removing the modules from the subrack.

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Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
Audio Connections
The Receiver, Transmitter and Auxiliary Balanced audio lines are available for connection on Zetron extender
cards or by connecting to the optional back panel A-PNL-AUX96-3 screw-type terminal connector. The
extender cards have solder points available on each signal line that can have a small test point (5059-
TP110300) that is supplied with the extender card, soldered to them for easy connection with clip-on type clips.
Recommended Test Points are:
Audio Control Card and Base Control Card Extender Card pins (EC-96D1 and EC-96K-1.22):
Auxiliary 1 Audio Output = B11 and A11
Auxiliary 2 Audio Output = C1 and C3 (Audio Control Card); C2 and C4 (Base Control Card) Auxiliary 1 Audio
Input = C19 and C20
Auxiliary 2 Audio Input = B14 and A14
Receiver and Transmitter Extender Card pins (EC-48RD and EC-48RK-1.22):
Rx Balanced Audio Output = B26 and Z26
Tx Balanced Audio Input = B18 and Z18
Tx Subtone Input = B22 and Ground (B32)
The test points can be soldered into the extender cards as shown in Figure H-1.
Figure H-1: EC-96D1 and EC-48RD Direct Connect Extender Cards with Test Points Added
test points soldered
onto extender card

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Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
SYSTEM REGULATOR TESTING
System Voltage Testing
The first stage of testing a Zetron MT-4E radio system is to perform a basic system check on the supply and
regulated voltages. The System Regulator module is designed with a convenient and easy test point built into
the front panel. This test point allows a technician access to the DC supply and regulated voltages. Simply
connect a standard Digital Volt Meter (DVM) to the METER jacks on the front panel of the System Regulator as
shown in Figure H-2.
Figure H-2: System Regulator Voltage Testing
The FUNCTION rotary switch on the front panel of the System Regulator will allow you to test various points in the
radio system. Following is a list of System Regulator rotary switch positions, the functions they measure and the
parameters measured:
1Supply Voltage +10 Vdc to +17 Vdc (+13�8 Vdc nominal)
2+9.5 Volts Regulated +9.5 Vdc (± 0.1 Vdc)
3Rx A Audio Receiver A Audio (NOT Rx Balanced Output)
4Rx A Carrier Strength 0 Vdc to +5.0 Vdc based on received signal strength
(0 Vdc is a low RF signal level, +5.0 Vdc is high)
5Rx B Audio Receiver B Audio (NOT Rx Balanced Output)
6Rx B Carrier Strength 0 Vdc to +5.0 Vdc based on received signal strength
(0 Vdc is a low RF signal level, +5.0 Vdc is high)
CANCEL
ms
AA
mA
XAM NIMXAM NIMDLOHDLOH LERLER
RANGE
RANGE
Hz
Hz %
%
ms
BdBd
BdBd
cd+cacd+ca
cd+cacd+ca
cd+cacd+ca
cd+cacd+ca
FF
mA
SnSn
AA
mAmA
mVmV
VV
mVmV
VV
OFFOFF
CC
AA
AA
AA MOCMOC VV
TEMPERATURETEMPERATURE
AmAm
AA
AutoHOLD LOGGING
SAVE
FAST MN MX
SETUP
YES
NO
DIGITAL MULTIMETER
CLEAR MEM
VIEW
DC
TRANSMITTER
CNTL
BUS
MIC
AD
RF OUT
ANALOG
NORM
DIGITAL
OFF
KEY TX
MICMODE
REF
IN
USB
FREQUENCY (MHz)
MADE IN CANADA
MODEL # CODE
RECEIVER
NORM
SQ. DISABLE
OFF
CNTL
BUS
AD
RF IN
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
67
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
Enter the Supply Voltage and +9.5 Volts Regulated values on the MT-4E Test Sheet. Inject a -100 dBm carrier
signal into the Receiver and record the RSSI Voltage on the MT-4E Test Sheet. Enter the Date, Firmware Versions
and Serial numbers of the Receivers and Transmitters on the MT-4E Test Sheet. The Firmware Version and Serial
Number can be found by connecting the RSS and clicking on Rx ID or Tx ID. The Serial Numbers can also be
found on the side of the modules.
The standby current draw of the radio system should be measured for battery / solar powered systems.
Connect an ammeter to the power input line and measure the standby current draw and transmit current draw
of the system. Enter the Standby Current Draw and Transmit Current Draw readings on the MT-4E Test Sheet. The
maximum standby and transmit current draw is dependent on the radio system (number and class of receivers,
transmitter output power, amplifiers, auxiliary equipment, etc.).

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Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
RECEIVER TESTING
Receiver Analog Testing
Connect the CX300 and Zetron Radio as shown in Figure H-3:
Figure H-3: Receiver Analog Testing
On the CX300, load Zetron preset 01 Rx Analog from your internal drive. Enter the correct RF frequency and
ensure that the deviation level of the 1.0 KHz tone is set correctly for your receiver (wide / narrow) in M1. Enter
the correct CTCSS tone (if used) and deviation level for the tone in M2. On the Zetron Radio system, ensure
the receiver is turned on and turn the System Regulator Speaker switch to ON and INT. Set the FUNCTION
rotary switch to position 3 for Rx A or position 5 for Rx B (depending on the receiver being tested), then turn the
volume up until the 1 KHz tone is audible.
Computer running RSS
USB from
Rx Balanced Audio Output
(from pins B26 and Z26)
Computer to Rx
RF OUTPUT from
CX300 to RF IN on Rx
AF INPUT 1
RECEIVER
SQ. DISABLE
OFF
NORM
BUS
CNTL
AD
RF IN
IN
REF
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
67
8
11
10
9
FUNCTION
12

08
Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
Figure H-4: Receiver Distortion Measurement
Audio Distortion:
To check receiver distortion, inject -70 dBm RF carrier level into the receiver and measure the distortion on the
meter as shown in Figure H-4. The high limit is set to 2.0 %.
Enter the Audio Distortion reading on the MT-4E Test Sheet.

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Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
Figure H-5: Receiver Reference Sensitivity Measurement
Reference Sensitivity:
To check receiver sensitivity, select DISTORTION on the screen to open the NOISE panel. Under TYPE, select
SINAD. Monitor the SINAD meter while slowly reducing the RF carrier level as shown in Figure H-5. The 12 dB
SINAD point should be at an RF carrier level less than the specified Analog Sensitivity point of the receiver. The
high and low limits are set at 11.5 dB and 12.5 dB SINAD.
Enter the Reference Sensitivity (12 dB SINAD) reading on the MT-4E Test Sheet.
If the distortion or reference sensitivity measurements are not within Zetron published specifi cations, the RF
Preselector may need re-alignment. Refer to the Receiver RF Preselector Alignment and Tuning section.
Squelch:
Adjust the RF carrier level up and down until the receiver squelches and unsquelches. There should be
approximately 6.0 dBm of hysteresis between the squelch and unsquelch points. The squelch point can be
adjusted in the Squelch Levels area of the Service section on the RSS.
The Receiver operates on a Noise based squelch (default) or a Received Signal Strength based squelch
(optional). The squelch can be set globally for all channels, or on a per channel basis. To set the squelch Open
and Close points, inject an RF signal at the desired Open or Close level and click the Set button.
Enter the Squelch and Unsquelch readings on the MT-4E Test Sheet.

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Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
Audio Level:
The audio level adjustment is not required when connecting the receiver in a repeater configuration using LVDS
Serial Data. The audio level adjustment can be done on both the Rx Balanced Audio Output and the Auxiliary
Balanced Output (1 and 2). The Auxiliary Balanced Output is only available on the AC-3E Control Card or CI-
BC-4E Base Control Card�
To adjust the receiver balanced audio output, ensure that the AC-3E Control Card or CI-BC-4E Base Control
Card is NOT plugged into the subrack, and inject -70 dBm RF carrier level into the receiver (no external load is
required as the internal 600 ohm load of the CX300 is used).
In the Audio Levels area of the Service section on the RSS, adjust the Rx Balanced Audio Output level
adjustment as shown in Figure H-6 until -8.0 dBm audio level (0.308 Vrms @ 600 ohms) is measured on the AF
Level meter of the CX300 as shown in Figure H-4.
Figure H-6: RSS Receiver Audio Level Adjustment
To adjust the auxiliary balanced audio output, plug the AC-3E Control Card or CI-BC-4E Base Control Card into
the subrack using an extender card and connect the Auxiliary Balanced audio output to the AF INPUT 1 on the
CX300 (no external load is required as the internal 600 ohm load of the CX300 is used). Auxiliary 1 audio output
is available on pins B11 and A11, and Auxiliary 2 audio output is available on pins C1 and C3 for the AC-3E
Control Card and pins C2 and C4 for the CI-BC-4E Base Control Card. Ensure that NO external devices (eg.
tone remote adapter or IP router) are connected to the auxiliary audio output. Adjust the Auxiliary Balanced
Audio Output level adjustment (R13 for Aux Out 1, R56 for Aux Out 2) for 0.0 dBm audio level (0.775 Vrms @ 600
ohms).
Enter the Balanced Audio Output Level and Auxiliary Audio Output Level (if used) readings on the MT-4E Test
Sheet.
There are no specific measurements to check Receive CTCSS, just verify that the receiver CTCSS is operating.

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Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
Receiver Digital / BER Testing
Connect the CX300 and Zetron Radio as shown in Figure H-7.
Figure H-7: Receiver Digital Testing
On the CX300, load Zetron preset 02 Rx Digital from your internal drive. Enter the correct RF frequency, and
ensure that the Mod Pattern is set for the Stored Speech test pattern (or optionally the 1011 test pattern).
Inject the correct NAC as shown in Figure H-8 and ensure that the receiver is operating. There are no specific
measurements to make on this test, just verify that the receiver is operating.
Figure H-8: Receiver Digital Check
Computer running RSS
USB from
Rx Balanced Audio Output
(from pins B26 and Z26)
Computer to Rx
RF OUTPUT from
CX300 to RF IN on Rx
AF INPUT 1
RECEIVER
SQ. DISABLE
OFF
NORM
BUS
CNTL
AD
RF IN
IN
REF
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
67
8
11
10
9
FUNCTION
12

12
Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
Receiver Bit Error Rate Testing
On the CX300, select the STD 1011 test pattern in the Pattern window under P25 Mod.
In the receiver RSS, enter the Service section and click on “Bit Error Rate”. The receiver frequency should
automatically be shown in the frequency box. Select the Test Type to “Continuous” and Avg. Superframes to
“8”. Click on the “Start Test” button to start the BER test. You should get 0% BER at the -70 dBm default RF carrier
level�
Monitor the BER reading while slowly reducing the RF carrier level as shown in Figure H-9. The 5% BER point
should be at an RF carrier level less than the specified Digital Sensitivity point of the receiver
Figure H-9: RSS Receiver Bit Error Rate Test
Enter the Reference Sensitivity (5% BER) reading on the MT-4E Test Sheet.
If the BER measurements are not within Zetron published specifi cations, the RF Preselector may need re-
alignment. Refer to the Receiver RF Preselector Alignment and Tuning section.

13
Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
Receiver RF Preselector Alignment and Tuning
Tuning of the RF Preselector filter is typically only required when the Analog or Digital Sensitivity or Analog
Distortion do not meet published specifications, or when the receiver RF frequency is changed beyond the
band pass of the filter (typically 5 - 7 MHz in a VHF or UHF 400 MHz receiver). The UHF 700 / 800 / 900 MHz
receiver RF Preselector is Full Band and does not require any tuning.
Connect the CX300 and Zetron Radio as shown in Figure H-10.
Figure H-10: Receiver RF Preselector Tuning
The RF Preselector output is a small RF cable internal in the receiver that terminates in an SMB connector.
The SMB plugs into J3 on the Receiver Mainboard. Disconnect the SMB cable from J3 and use the SMB-BNC
adapter to connect this point to the RF INPUTon the CX300 as shown in Figure H-11.
Figure H-11: Receiver RF Preselector Connection
RF Preselector output
from Receiver to
RF INPUT on CX300
RECEIVER
SQ. DISABLE
OFF
NORM
BUS
CNTL
AD
RF IN
IN
REF
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
67
8
11
10
9
FUNCTION
12
RF OUTPUT from
CX300 to RF IN on Rx
J3
on CX300
To RF INPUT
RF Preselector
output

14
Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
On the CX300, load Zetron preset 03 Rx Preselector Tune from your internal drive. Enter the correct RF frequency
as the Center Freq and ensure the receiver is turned on. The filter waveform should appear as shown in Figure
H-12�
Figure H-12: Receiver RF Preselector
To tune the RF Preselector filter, remove the dust caps on the variable capacitors and, starting from the
capacitor closest to the front panel of the receiver and moving back, tune the filter to its new frequency.

15
Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
Receiver Reference Oscillator Adjustment
Connect the CX300 and Zetron Radio as shown in Figure H-13.
Figure H-13: Receiver Reference Oscillator Testing
The reference oscillator test on the receiver requires a connection directly into the Synthesizer, which uses an
SMB connector. Disconnect the SMB cable from the LO output of the synthesizer and connect the small SMB-
SMB cable to the SMB jack that is mounted on the Synthesizer (beneath the RF Preselector). The SMB-BNC
adapter is required to connect this point to the RF INPUT on the CX300 as shown in Figures H-14 (VHF and UHF
400 MHz Receiver) and H-15 (UHF 700 / 800 / 900 MHz Receiver).
Figure H-14: VHF and UHF 400 MHz Receiver Reference Oscillator Connection
Synthesizer L.O. output
from Receiver to
RF INPUT on CX300
Computer running RSS
USB from
Computer to Rx
RECEIVER
OFF
NORM
SQ. DISABLE
BUS
CNTL
AD
RF IN
IN
REF
USB
FREQUENCY (MHz)
MADE IN CANADA
MODEL # CODE
VOL
SYSTEM REGULATOR
METER
+
-
MADE IN CANADA
ON
OFF
EXT
SPKR
INT
EXT
SPKR
OFF
POWER
ON
2
1
5
4
3
67
8
11
10
9
FUNCTION
12
on CX300
SMB-SMB To RF INPUT
cable
LO output of
synthesizer

16
Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
Figure H-15: UHF 700 / 800 / 900 MHz Receiver Reference Oscillator Connection
On the CX300, load Zetron preset 04 Rx Reference from your internal drive as shown in Figure H-16.
Figure H-16: Receiver Reference Oscillator Measurement
on CX300
SMB-SMB
cable To RF INPUT
LO output of
synthesizer

17
Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
Figure H-17: RSS Receiver Reference Oscillator
Alignment
In the receiver RSS, enter the Service section and click on “Ref Oscillator”. The reference oscillator frequency is
shown as the “Target Synthesizer RF OUT”. Enter this RF frequency into the frequency on the CX300. The receiver
generates this frequency out of the Synthesizer into the CX300.
Monitor the RF Error on the CX300. To change the reference frequency, adjust the softpot slider in the RSS as
shown in Figure H-17. Adjust until the RF Error is as close to 0 Hz as possible. Click on the “Program” button to
program in the new Reference Oscillator softpot value.
Enter the L.O. Reference Oscillator Offset reading on the MT-4E Test Sheet.

18
Appendix H: Viavi CX300 Tests
MAINTENANCE GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
TRANSMITTER TESTING
Transmitter Analog Testing
Connect the CX300 and Zetron Radio as shown in Figure H-18.
Figure H-18: Transmitter Analog Testing
On the CX300 load Zetron preset 05 Tx Analog from your internal drive. Enter the correct RF frequency on the
CX300, set the MIC MODE switch on the front panel of the transmitter to Analog, and flip the other switch to KEY
TX (or set the switch to NORM and key the transmitter through the RSS).
The AF Generator A1 is configured to inject a 1.0 KHz tone at -8.0 dBm (0.308 Vrms) into the transmitter
balanced input as shown in Figure H-19.
Computer running RSS
Tx Balanced Audio Input
(to pins B18 and Z18)
USB from
Computer to Rx
Tx RF OUT to
RF DUPLEX on CX300
TRANSMITTER
BUS
CNTL
MIC
AD
RF OUT
DIGITAL
OFF
NORM
KEY
ANALOG
TX
MICMODE
IN
REF
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
67
8
11
10
9
FUNCTION
12
AF OUTPUT