radio power for using unlicensed RF bands towards municipal wifi

[Mark Rosenblitt-Janssen]

Here's some new data for the radio jockeys making muni wifi and mesh networking a reality.  This data will give you some figures to use for minimzing trouble with the FCC.  They are public bands and power limits have been made extremely defendible.

In short, for municipal-range radio:

1. 2 mile transmission range limit from unlicensed operators (as measured by single-axis, passive antennae (without gain)) one-way transmission. "Range" here means you shouldn't be able to tune a signal on an passive antenna at said distance.
2. Any single transmitter can't be over 500W regardless of distance.
3. Frequency recommendations: CB CH1 can be set aside for datacomm. UPDATE: CH2 may be better, leaving odd numbers for voice and even for future data(?). Old UHF bands are also a good bet (channels 32-34, (477.2000-477.2500MHz) are supposedly set aside. Try those first. Stay away from 2-way radio bands and any emergency bands.
4. 50W²/1mile-diameter-circle total radiation (within specified wavelengths), and less if you don't need it. This means, if you're using 5 radios, then 10W per device, two radios 25W, etc.  This is not a suggested power: you must attenuate your transmitter until you get under the range requirement. Different ambient radio environments make different challenges, but the first requirement nails down your limit. 
5. Stay polite: Attenuate radio power from maximum if ambient radio space and device distances allow it. Two people in a coffee shop shouldn't need to be at 25W a piece. Mesh networkers: To this end, also limit continuous broadcast (any beacon node) to a maximum of 1 hour at a time. and no more than 50% duty-cycle for any beacon nodes (15 min beaming your sentinal datapacket, 3/4-hour of radio silence is probably best). (This shouldn't be a problem as you'll be so popular that they'll be plenty of nodes offering service, right?)
6. Some experimentation may be allowed if you're licensed operator outside the bands given above. Stay off licensed spectra and any bands used for emergencies (medic alert, CB CH9, etc.), and it's always polite to check a band before transmitting (a hand-held HAM radio should suffice). For the sake of the community, consider any unknown transmission as possibly licensed and legit, until deduced or traced otherwise.
7. If you are a licensed operator, as a courtesy and a possible benefit to yourself, you should place your call-sign in all datalink (and maybe the transport layer to keep your work associated after the datalink layer is stripped off) packets somewhere (it's only 6 bytes).
8. Probably don't use on commercial aircraft.

If you want to eliminate the range limitation, you can move power down to 1/2 the given limit (25W/mile-radon, 12.5W for two devices), and limit yourself to CB CH1 and UHF 32-34. If you have an antennae solution that allows you to receive at 1000 miles at 25W, you must have some very fine tuners.

This  info taken from wiki.hackerspaces.org  This is a rough excerpt.  Check it out.

[\0xDynamite]

I forgot to say: please check with original site before using this
data. It's been hidden by some wiki boneheads, so search under
"Everything" if necessary.

> This info taken from wiki.hackerspaces.org This is a rough excerpt.
> Check it out.

\0xD