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Thorn · 06-03-2002

Q: I want to have a high powered AP (or Mobile.) What are the legal limits to adding a Radio Frequency amplifier?

A: The unlicensed use, legal limits for 802.11b are 30dB (1 Watt) effective radiated power for a Point-to-MultiPoint (PtMP) transmission, and 36dB (4 Watts) for a Point-to-Point (PtP). Effective radiated power is the output seen at the antenna.

To calculated the power output, take the final output from the devices, such as the AP or AP and amp, subtract any line losses from the coax and connectors, and add the gain of the antenna. To illustrate: Assuming for argument's sake a 1 Watt (30dB) amp, a 2dB line loss and a 5dB omni. (30 - 2) + 5 = 33 dB (2 Watts) output. Clearly illegal for anything but a PtP setup. To be legal with this antenna combination, you would need to have no more that a 27 dB (.5 Watt) amp. (27 - 2) + 5 = 30.

BTW, these power limits are for general public unlicensed use for 802.11b. Amatuer (ham) also use the 2.4Ghz area, and the hams have different power output limitations. However, hams can't use this for any business purposes.

Attached to the next message is a small text chart which shows the releationship of MilliWatts and Watts, to decibels.

06-03-2002	#25 (permalink)
Thorn Did you do the math? Join Date: Apr 2002 Location: Villa Straylight Posts: 10,360	RF Power Q: I want to have a high powered AP (or Mobile.) What are the legal limits to adding a Radio Frequency amplifier? A: The unlicensed use, legal limits for 802.11b are 30dB (1 Watt) effective radiated power for a Point-to-MultiPoint (PtMP) transmission, and 36dB (4 Watts) for a Point-to-Point (PtP). Effective radiated power is the output seen at the antenna. To calculated the power output, take the final output from the devices, such as the AP or AP and amp, subtract any line losses from the coax and connectors, and add the gain of the antenna. To illustrate: Assuming for argument's sake a 1 Watt (30dB) amp, a 2dB line loss and a 5dB omni. (30 - 2) + 5 = 33 dB (2 Watts) output. Clearly illegal for anything but a PtP setup. To be legal with this antenna combination, you would need to have no more that a 27 dB (.5 Watt) amp. (27 - 2) + 5 = 30. BTW, these power limits are for general public unlicensed use for 802.11b. Amatuer (ham) also use the 2.4Ghz area, and the hams have different power output limitations. However, hams can't use this for any business purposes. Attached to the next message is a small text chart which shows the releationship of MilliWatts and Watts, to decibels. __________________ Thorn "Read Altas Shrugged. Compare it to today. Repeat as necessary"