Here are the pertinent bits as far as I can tell:

• Radios(Transmitters) are limited to 30dBm (or 1 watt) of output (NO exceptions)

• For a multipoint antenna you are limited to 36dBm EIRP (total output)
• For a antenna that will only ever talk to one other antenna there is no maximum limit but you have to follow a formula. Your transmitter's power is determined by 30dBm-((antenna gain-6)/3). i.e. If you are using a 15dB antenna it would be 30dBm-((15-6)/3) so your transmitter can put out 27dBm (or 500mw) into a 15dB antenna making your EIRP 42dBm (or 64 watts)

There is a little dBm <-> Watt conversion utility here: http://www.kirkeby.it/html/playground/swr.html

(NOTE: some people view the FCC rules as only allowing an omnidirectional antenna a total of 30dBM EIRP, but the general consensus is that they are really directional (they do limit the vertical beamwidth) and follow the same rules as every other type of antenna)

-MichaelCodanti

SeattleWireless has some information on this too: http://www.seattlewireless.net/index.cgi/FccRegulations

Its pretty dense though, so whoever's got the ability to read that or already knows it please summarize!

-ColinDabritz

Here's a good summary from TimPozar at BaWug

• http://www.lns.com/papers/FCCPart15_and_the_ISM_2.4G_Band.index

and another more recent paper by Tim here (PDF or Postscript):

• http://www.lns.com/papers/part15/

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