GE GFK-2489 - Manual (Page 144)

GFK-2489 Chapter 6 Installation 6-11
6
For convenience, the table below 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 (1 Watt).
Antenna System Gain Maximum Power
(Antenna Gain in dBi* Setting EIRP minus
Feedline Loss in dB†) (in dBm) (in dBm)
6 (or less) 30 36
8 28 36
10 26 36
12 24 36
14 22 36
16 20 36
* 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, as shown previously.
How Much Output Power Can Be Used? (U.S.A. and Canada, 2400 MHz
systems)
Non-ETSI 2400 MHz transceivers are normally supplied from the factory set for +27 dBm (0.5
Watt) 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 0 dBi. The allowable level depends on the antenna gain, feed-line loss, and the
transmitter output power setting. In regions where ETSI requirements 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.
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 27 dBm (the maximum allowable EIRP). The
result indicates the maximum transmitter power (in dBm) allowed under the rules. In
the example above, this is 19 dBm.
3. If the maximum transmitter power allowed is less than 27 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 27 dBi.