The FCC regulations for PtMP allows only 36 dBm (4 watts) EIRP when omni antennas are used. This is 30 dBm (1 watt) into a 6 dBi antenna.  If you use a 10 dBi omni antenna, you must limit your transmitter (or amplifier) to 26 dBm (10 + 26 = 36 dBm). For a PtP panel antenna, more power is allowed (see separate FAQ on this). Power is measured at the antenna connector, so subtract any cable loss between the amplifier and the antenna. Refer to the following table:

Yes, up to the highest gain antenna specified in the FCC certification information or the product literature that accompanies the device. (See FCC 04-165 adopted July 8, 2004, 15.204(c)) Those people in countries other than the US will need to consult their own regulations. If you are not sure if the antenna that you plan to use is certified or authorized with the radio system, ask the radio or antenna manufacturer/vendor. If you have the radio FCC ID, you can check on the FCC web site for certification information.

According to FCC regulations, 2.4 GHz Part 15.247 point-to-point transmitters may use a 30 dBm transmitter with a 6 dBi antenna. For a 3 dB increase in antenna gain, the transmitter power output must be reduced by 1 dB. Power is measured at the antenna connector, so subtract any cable loss between the amplifier and the antenna. Refer to the following table. (also see Canadian Rules)

If the CPE system (or Subscriber Unit - SU) only talks with the POP/AP and is at a fixed location, then it is considered to be PtP and can use power and antenna gain associated with PtP systems, as shown below. (This has been verified by FCC Certified systems using a 26 dBm radio and a 17 dBi antenna) If a CPE system is part of a mesh network, then it is considered PtMP.

Currently, most systems use either IEEE 802.11 or 802.11b operating between 2.4 and 2.4835 GHz.  As these frequencies become more congested, the U-NII Band 3 at 5.725 - 5.825 GHz (IEEE 802.11a) will be used more.  5.8 GHz also offers data transmission rates greater than 11 MB/s.  However, more antenna gain will be necessary at 5.8 GHz for the same distance on 2.4 GHz.  5.8 GHz will have a smaller Fresnel zone, so there may be certain advantages when shooting a signal through a tight space between trees or buildings. The WCS and MMDS frequencies between 2.1 and 2.7 GHz are also available to FCC-licensed users. (See IEEE 802.16a)