GE MDS entraNET 900, Техническое руководство

Страница: 166 / 220

156 MDS entraNET Technical Manual 05-4055A01, Rev. E
6.2 HOW MUCH OUTPUT POWER CAN
BE USED?
(U.S.A. and Canada, 900 MHz systems)
900 MHz transceivers are normally configured from the factory for
+30 dBm (1 W) RF power output. This is the maximum transmitter
output power allowed under FCC and Industry Canada 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.
NOTE:
In regions where ETSI standards apply, the maximum
allowable RF output is generally limited to 100 mW
(+20 dBm) on 2400 MHz. License-free operation on 900 MHz
is not permitted. For more information, see
HOW MUCH
OUTPUT POWER CAN BE USED? (ETSI 2400 MHz systems)
on Page 158.
6.2.1 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 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,
reduce the transmit power accordingly using the radio menu system
(
Main Menu>Radio Configuration>RF Output Power Setpoint
), or introduce
additional feedline loss. The EIRP of the antenna system should
never exceed 36 dBi.
For convenience, Table 6-4 on Page 157 lists several antenna system
gains and shows the maximum allowable power setting of the radio.