How Much Output Power Can Be Used; Output Power); Antenna System Gain Vs. Power Output - Microwave Data Systems MDS TransNET 900 Installation & Operation Manual

3.5 How Much Output Power Can be Used?

The transceiver is normally supplied from the factory set for a nominal
+30 dBm (1 Watt) RF power output setting; this is the maximum transmitter
output power allowed under FCC rules. The power must be decreased from
this level if the antenna system gain exceeds 6 dBi. The allowable level is
dependent on the antenna gain, feedline loss, and the transmitter output power
setting. Power considerations for the MDS TransNET 900 are discussed
below.
In some countries, the maximum allowable RF output may be
NOTE:
limited to less than 1 watt (e.g., 100 mW / +20 dBm). Be sure to
check for and comply with the requirements for your area.
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 in your region is less than 30
dBm, use the
accordingly.
For convenience,
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 (1 watt).
Table 3. Antenna system gain vs. power output setting (USA)
Antenna System Gain
(Antenna Gain in dBi*
minus Feedline Loss in dB†)
6 (or less)
* 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
12 MDS TransNET 900 I&O Guide
command (described on
PWR
Table 3 lists several antenna system gains and shows the
8
10
12
14
16
Page 34) to set the power
Maximum Power
Setting
(in dBm)
30
28
26
24
22
20
Table 2 on Page
MDS 05-2708A01, Rev. B
EIRP
(in dBm)
36
36
36
36
36
36
11.