MDS iNET 900 - Antenna System SWR and Transmitter Power Output; Introduction; Procedure

92 MDS iNET 900 User’s Guide MDS 05-2806A01, Rev. A
These procedures may interrupt traffic through an established network
and should only be performed by a skilled radio-technician in coopera-
tion with the network manager.
4.2.1 Antenna System SWR and Transmitter Power
Output
Introduction
A proper impedance match between the iNET 900 and the antenna
system is important. It ensures the maximum signal transfer between the
radio and antenna. The impedance match can be checked indirectly by
measuring the SWR (standing-wave ratio) of the antenna system. If the
results are normal, record them for comparison for use during future
routine preventive maintenance. Abnormal readings indicate a possible
trouble with the antenna or the transmission line that will need to be cor-
rected.
The SWR of the antenna system should be checked before the radio is
put into regular service. For accurate readings, a wattmeter suited to
1000 MHz measurements is required. One unit meeting this criteria is
the Bird Model 43
™
directional wattmeter with a 5J element installed.
The reflected power should be less than 10% of the forward power
(≈2:1 SWR). Higher readings usually indicate problems with the
antenna, feedline or coaxial connectors.
If the reflected power is more than 10%, check the feedline, antenna and
its connectors for damage.
Record the current transmitter power output level, and then set it to
30 dBm for the duration of the test to provide an adequate signal level
for the directional wattmeter.
Procedure
1. Place a directional wattmeter between the
ANTENNA connector and
the antenna system.
2. Place the iNET unit into the Radio Test Mode.
(Main Menu>Diagnostic Tools>Radio Test>Test Mode>Y>ON)
NOTE: The Test Mode has a 10-minute timer, after which it will
return the iNET unit to normal operation. The Radio Test Mode can
be terminated manually.
3. Set the transmitter power to 30 dBm.
(Main Menu>Diagnostic Tools>Radio Test>Test Mode>
Tx Power Output)
NOTE: The Radio Test Mode RF power setting will not affect the
output level during normal operation.