GE GFK-2489 - Manual (Page 145)

6-12 TranSphere TS Wireless Extended Range IP Networking Transceivers – January 2008 GFK-2489
6
For convenience, the table below lists several antenna system gains and shows the maximum
allowable power setting. Note that a gain of 0 dB entitles you to operate the radio at full power
output 27 dBm (0.5 Watt).
Antenna System Gain versus Power Output Setting (U.S.A. and Canada only)
Antenna System Gain Maximum Power
(Antenna Gain in dBi* Setting EIRP
minus Feedline Loss in dB†) (in dBm) (in dBm)
0 27 27
5 22 27
7 20 27
9 18 27
12 15 27
15 12 27
* 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.
How Much Output Power Can Be Used? (ETSI 2400 Mhz Systems)
In regions where ETSI requirements apply, 2400 MHz transceivers are supplied from the
factory with a +20 dBm (100 mW) RF power setting; this is the maximum EIRP transmitter
output power allowed under ETSI standards. The power must be decreased from this level if
the antenna system gain exceeds 0 dBi. The allowable level is dependent on the antenna
gain, feedline loss, and the transmitter output power setting.
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.
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