Installation Guide

Cable Loss and Transmit Power Settings
LIG0002AC Rev G
When setting up the network, consider the power gain that an antenna may add, and the power loss through
cabling. Adjust the Transmit Power on the transceiver to ensure that you do not exceed the maximum EIRP
for the regulating body where the installation exists. Use the tables below to determine the correct Transmit
Power parameter setting for each transceiver in the network.
Important: The information in this section discusses FCC and ETSI maximum EIRP
regulations. Ensure your installation meets the maximum EIRP requirements for the
country in which you are installing transceivers. It remains the installer's responsibility
to ensure that an installation is within EIRP emission limits.
The FCC permits 27 dBm (0.5 Watt) output power at the transceiver and 36 dBm (4 Watts) at the antenna.
ETSI permits a total of 20 dBm (100 mW) total, which includes the output power at the transceiver and the
antenna gain.When calculating the power gain, use the following equation to determine the total output power
at the antenna.Loss calculations should include cable, connectors, surge protectors, and so on.
Transceiver Output – Losses + Antenna Gain = Output Antenna Power
For example, 30 dBm – 2 dB + 6 dB = 34 dBm (or 2.5 Watts). 34 dBm is within the FCC limits. However,
30dBm – 2dB + 10dB = 38 dBm (or 6.3 Watts) exceeds the FCC limits. Neither is permitted under ETSI
regulations.
The following table shows the RF loss at various cable lengths:
Cable Type
Length in Feet LMR240 LMR400
10 1.3 dB 0.7 dB
20 2.6 dB 1.4 dB
25 3.2 dB 1.7 dB
30 3.9 dB 2.1 dB
50 6.5 dB 3.4 dB
100 12.9 dB 6.8 dB
In GX family transceivers, the Transmit Power parameter settings range from 0 dBm to 27 dBM (1 mW to
500 mW). The maximum transmit power is capped at 20 dBm at the factory to comply with ETSI regulations
for countries that require it, or capped at other values to comply with country-specific requirements.
The output power can vary slightly between transceivers; however, the output power never exceeds 27dBm
(500 mW).
The following table provides the maximum Transmit Power parameter setting for FreeWave transceivers at a
given antenna gain and cable loss combination. 5 dBi antennas are used in this example.
Cable Loss
Antenna Gain
1 dB 2 dB 3 dB 4 dB
5 dBi Point-to-Point 27 27 27 27
5 dBi Point-to-MultiPoint 27 27 27 27
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