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
A D
RF I N
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
6
7
8
11
10
9
FUNCTION
12
RF OUTPUT from
CX300 to RF IN on Rx
J3
on CX300
To RF INPUT
RF Preselector
output
