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Originally Posted by fesstech
... I think i read that the transmission power of the phone transceiver is limited to 200mw FCC regulation. I am sure the same or other regulations apply to the bluetooth and wifi. Correct me if i'm wrong.
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Unlicensed usage of the 2.4Ghz band (802.11x, and Bluetooth) Is limited to 200mw omni-directional per FCC reg. the FCC does allow power output upto 1w if proper directional attenas are used. Bluetooth is intended to be a PAN Protocol (Personal Area network) and standards limt the power output to around 25mw, and most devices run in the 10-25mw range. With 802.11x most devices only output around 100mw and is a defacto-standard. Now if you wanna drool, Extra-class Licensed Amature radio opeators are allowed to run 1 kw output power (omni-directional) in the 2.4ghz band and allow more power to be used if a directional attena is used (i cant rember the max).
With most comercial band cellular (800mhz and 1900mhz, i dont know about the others) the FCC limits 500mw omni-directional and again has provisions for directional attena at higher power outputs.
for thoes that dont know, omni-directional refres to the the attena outputing in all directions, think car attena, where directional refres to the signal only being sent in one area, think pringles can attena. The FCC allows for higher output powers over directional orintated links as they preduce less cross band interfearance because the signl only occupys a small percentage of the airwaves, where an omni-directional attena sends out everywhere polluting all of the airwaves around it.
If you want another exmaple consider how much ligh is emited by a lightbulb, if placed in the center of a empty room, it will illuminate the room, this is the same effect an omni-direction attena would have, now, replace the light bulb with a laser pointer, the laser pointer will only illuminate a verry verry small percentage of the room, this is the effect of a (proper)directional attena. and hence why you are only allowed to use a dim lightblub, but a bright laser pointer.
~X