OT: 802.11b freq's

EC-7 · Post by **EC-7** » Wed Apr 03, 2002 7:21 am

Sorry this is a little off topic, but concerns to RF.

Does anyone know the freq's for 802.11b wireless. What are the power limits set by the FCC, and what is the average power of a tranciever? I want to set up a small city wide wireless network. Will I get any advantage over a 56k modem, on speed? I can set it up on a hill in the town I live in and I need a 3-5 mile radious, if possible. Thanks for any help.

PRR · Post by **PRR** » Wed Apr 03, 2002 9:43 am

The frequency range is 2.4000 - 2.4835GHz in the FCC domain (2.9GHz in Japan). I believe the absolute maximum RF power at the connector allowed is 100mW. There is however a gain vs. dispersion scale that I believe allows for a maximum of +46dbm ERP at 10 degrees horizontal (for point to point bridges). If you need firm numbers, I can look them up.

I've found that all the sub $700.00 access points are 35 - 65mW, as are all PC cards - except for the Cisco 350 series: The entire line is 100mW.

802.11b is a 10baseT equivalent so it can give you a maximum of 10Mbps. Keep in mind that as signal strength diminishes due to distance, line of sight obstructions (and at 2.4GHz, line of sight becomes a nasty issue) and/or spectrum crowding, that rate can fall back to as little as 1Mbps.

Lastly, 802.11b was not designed for Wide Area Network (WAN): It is Local Area Network (LAN). Not only would it be in violation of FCC regs to have omnidirectional coverage of 3 - 5 miles (point to point using directional antennas would be fine), but you'll no doubt cause some intermittent disturbance to other 2.4GHz ISM and WiLAN systems.

Henry

techie · Post by **techie** » Wed Apr 03, 2002 3:47 pm

There are a couple mailing lists devoted to wireless networking, with an emphasis on 802.11b.. lots of folks doing Wireless ISP's, neighborhood networks, etc..
see http://www.bawug.org

Batman · Post by **Batman** » Wed Apr 03, 2002 7:08 pm

your allowed 1w into the antenna. and allowed an antenna of 6db and the wattage has to be droped by 1db for every 3db over 6 on the antenna.

Robert P. Chrysafis (batman)(kc8gpd)

go to this link

http://www.qsl.net/n9zia/

PRR · Post by **PRR** » Thu Apr 04, 2002 4:00 am

On 2002-04-03 22:08, Batman wrote:
your allowed 1w into the antenna. and allowed an antenna of 6db and the wattage has to be droped by 1db for every 3db over 6 on the antenna.

This power scale is for Frequency Hopping Spread Spectrum (FHSS): 802.11b is Direct Sequence Spread Spectrum (DSSS).

Henry

evanh · Post by **evanh** » Thu Apr 04, 2002 3:59 pm

<div align="center"><center><table border="1" cellspacing="0" bgcolor="#C0C0C0"bordercolor="#000000" bordercolordark="#000000"bordercolorlight="#000000"><tr><td bgcolor="#000000" bordercolor="#FFFFFF"bordercolordark="#000000" bordercolorlight="#FFFFFF"><blockquote>Channel</blockquote></td><td bgcolor="#000000" bordercolor="#FFFFFF"bordercolordark="#000000" bordercolorlight="#FFFFFF"><blockquote>Frequency (GHz)</blockquote></td></tr><tr><td>1</td><td>2.412</td></tr><tr><td>2</td><td>2.417</td></tr><tr><td>3</td><td>2.422</td></tr><tr><td>4</td><td>2.427</td></tr><tr><td>5</td><td>2.432</td></tr><tr><td>6</td><td>2.437</td></tr><tr><td>7</td><td>2.442</td></tr><tr><td>8</td><td>2.447</td></tr><tr><td>9</td><td>2.452</td></tr><tr><td>10</td><td>2.457</td></tr><tr><td>11</td><td>2.462</td></tr></table></center></div>

[ This Message was edited by: evanh on 2002-04-04 19:06 ]