05-2806A01, Rev. L
MDS iNET Series Reference Manual
113
Access Points” on Page 9.) Additional isolation can be achieved by using separate directional antennas
with as much vertical or horizontal separation as is practical.
•
If constant interference is present in a particular frequency zone (collection of 8 RF channels), it may be
necessary to “skip” that zone from the radio’s hopping pattern. The radio includes built-in software to
help users identify and remove blocked frequency zones from its hopping pattern. See Page 44 for more
information on Skip Zones.
•
If interference problems persist even after skipping some zones, try reducing the length of data streams.
Groups of short data streams have a better chance of getting through in the presence of interference than
do long streams.
•
The power output of all radios in a system should be set for the lowest level necessary for reliable com-
munications. This lessens the chance of causing unnecessary interference to nearby systems.
If you are not familiar with these interference-control techniques, contact your factory representative for
more information.
Calculating System Gain
To determine the maximum allowable power setting of the radio, perform the following steps:
1. Determine the antenna system gain by subtracting the feedline loss (in dB) from the antenna gain (in
dBi). For example, if the antenna gain is 9.5 dBi, and the feedline loss is 1.5 dB, the antenna system
gain would be 8 dB. (If the antenna system gain is 6 dB or less, no power adjustment is required.)
2. Subtract the antenna system gain from 36 dBm (the maximum allowable EIRP). The result indicates the
maximum transmitter power (in dBm) allowed under the rules. In the example above, this is 28 dBm.
3. If the maximum transmitter power allowed is less than 30 dBm, set the power to the desired level using
the Management System.
(
Main Menu>>Radio Configuration>>RF Output Power Setpoint
)
For convenience, Table 4-3 lists several antenna system gains and shows the maximum allowable power
setting of the radio. Note that a gain of 6 dB or less entitles you to operate the radio at full power output
–30 dBm (28.7 dBm for iNET-II).
* Most antenna manufacturers rate antenna gain in dBd in their literature. To convert to dBi, add 2.15 dB.
† Feedline loss varies by cable type and length. To determine the loss for common lengths of feedline, see
For assistance in the conversion of dBm to Watts, see “dBm-Watts-Volts Conversion Chart” on Page 117.
4.1.9 Notes on Using 28 VDC Power Supplies
Common 28 Vdc supplies are often high-current power supplies designed primarily to charge battery banks.
The radio can be operated from these supplies, providing there are no transients on the leads as power is
applied to the radio. Transients can be created that rise above 30 Vdc to a voltage that exceeds the primary
voltage rating of the radio and can destroy its voltage regulators and other components. It is important to
keep this potential hazard in mind when designing 28 Vdc power supply connections for the radio.
Table 4-3. Antenna System Gain vs. Power Output Setting
Antenna System Gain
(Antenna Gain in dBi*
minus Feedline Loss in dB†)
Maximum Power Setting
(PWR command)
iNET Radio
Maximum Power Setting
(PWR command)
iNET-II Radio
EIRP
(in dBm)
Omni 6 (or less)
30
28
36
Omni 11.14
24
23
36
Summary of Contents for MDS iNET Series
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