Sec. 15.407 General technical requirements.

(a) Power limits:

(1) For the band 5.15-5.25 GHz, the peak transmit power over the frequency band of operation shall not exceed the lesser of 50 mW or 4 dBm + 10logB, where B is the 26-dB emission bandwidth in MHz. In addition, the peak power spectral density shall not exceed 4 dBm in any 1-MHz band. If transmitting antennas of directional gain greater than 6 dBi are used, both the peak transmit power and the peak power spectral density shall be reduced by the amount in dB that the directional gain
of the antenna exceeds 6 dBi.

(2) For the band 5.25-5.35 GHz, the peak transmit power over the frequency band of operation shall not exceed the lesser of 250 mW or 11 dBm + 10logB, where B is the 26-dB emission bandwidth in MHz. In addition, the peak power spectral density shall not exceed 11 dBm in any 1-MHz band. If transmitting antennas of directional gain greater than 6 dBi are used, both the peak transmit power and the peak power spectral density shall be reduced by the amount in dB that the directional gain of the antenna exceeds 6 dBi.

(3) For the band 5.725-5.825 GHz, the peak transmit power over the frequency band of operation shall not exceed the lesser of 1 W or 17 dBm + 10logB, where B is the 26-dB emission bandwidth in MHz. In addition, the peak power spectral density shall not exceed 17 dBm in any 1-MHz band. If transmitting antennas of directional gain greater than 6 dBi are used, both the peak transmit power and the peak power spectral density shall be reduced by the amount in dB that the directional gain of the antenna exceeds 6 dBi. However, fixed point-to-point U-NII devices operating in this band may employ transmitting antennas with directional gain up to 23 dBi without any corresponding reduction in the transmitter peak output power or peak power spectral density. For fixed, point-to-point U-NII transmitters that employ a directional antenna gain greater than 23 dBi, a 1 dB reduction in peak transmitter power and peak power spectral density for each 1 dB of antenna gain in excess of 23 dBi would be required. Fixed, point-to-point operations exclude the use of point-to-multipoint systems, omni directional applications, and multiple collocated transmitters transmitting the same information. The operator of the U-NII device, or if the equipment is professionally installed, the installer, is responsible for ensuring that systems employing high gain directional antennas are used exclusively for fixed, point-to-point operations.

In the 802.11a frequency range there are three distinct 100MHz bands
UNII-1: 5.15GHz to 5.25GHz/Max output of 40mW and only used indoors
UNII-2: 5.25GHz to 5.35GHz/Max output of 200mW and used in and outdoors
UNII-3: 5.725 to 5.825GHz/Max output of 800mW and used outdoors

POINT to MULTI-POINT link:
The same intentional radiator power limit applies for all three bands. when using a maximum antenna gain of 6dBi. If the antenna gain is greater then the 1:1 rule applies, for each 1dB of gain above the 6dBi then 1dB of power from the intentional radiator must be reduced by 1dB

Max in UNII-1: 40mW=16dBm, so 16dBm+6dBi=22dBm or 160mW
Max in UNII-2: 200mW=23dBm, so 23dBm+6dBi=29dBm or 800mW
Max in UNII-3: 800mW=29dBm, so 29dBm+6dBi=35dBm or 3200mW

POINT to POINT link:
FCC uses the POINT to MULTIPOINT EIRP power ratings for UNII-1 and UNII-2 in POINT to POINT links. UNII-3 can use 800mW at the intentional radiator with an maximum antenna gain of 23dBi before the 1:1 rule applies. Which means 29dBm+23dBi=52dBm or 200Watts EIRP.