Calculating System Gain - GE MDS entraNET 900 Technical Manual

05-4055A01, Rev. E
NOTE: Some EU countries mandate lower power outputs and
frequency limitations from those referenced here. For
example, in France, the transceiver may only be operated in
band C (2.4528-2.4782 GHz) at a power level of 10 dBm. Be
sure to check the requirements for your region before placing
the transmitter on the air.

6.4.1 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 10 dBi, and the feedline loss is 2 dB, the antenna system gain
is 8 dB.
2. Subtract the antenna system gain from 20 dBm (the maximum
allowable EIRP). The result indicates the maximum transmitter
power (in dBm) allowed under the rules. In the example above, this
is 12 dBm.
3. If the maximum transmitter power allowed is less than 20 dBm,
reduce the transmit power accordingly using the radio menu system
(
Main Menu>Radio Configuration>RF Output Power Setpoint
additional feedline loss. The EIRP of the antenna system should
never exceed 20 dBi.
For convenience, Table 6-6
the maximum allowable power setting of the radio. Note that a gain of
0 dB or less entitles you to operate the radio at the full power output of
+20 dBm (100 mW). To convert dBm to Watts, refer to
Page 193.
Table 6-6. Antenna System Gain versus Power Output Setting
Antenna System Gain
(Antenna Gain in dBi*
minus Feedline Loss in dB†)
0 (or less)
3
6
9
10
* Most antenna manufacturers rate antenna gain in dBd in their litera-
ture. 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
MDS entraNET Technical Manual
lists several antenna system gains and shows
(for ETSI compliance)
Maximum Power
Setting
(in dBm)
20
17
14
11
10
Table 6-2 on Page
), or introduce
Table 8-4 on
EIRP
(in dBi)
20
20
20
20
20
155.
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