[Commotion-discuss] antenna dbi

[Andy Gunn]

Whoops, that second link broke, sorry:
http://www.antennas-amplifiers.com/image/cache/data/Wireless2/OV/13/Dual
OV13-3D-radiation-pattern-1000x1000.jpg


On 04/16/2015 10:22 AM, Andy Gunn wrote:
> For an omnidirectional antenna, the maximum total EIRP (effective
> isotropic radiated power - i.e. how much energy is coming out of the
> antenna) is 36dBm, or 4 watts.
> 
> So, with a 600mW Wi-Fi device (28dBm), you can have an additional 8 dB
> of antenna gain (normally stated as dBi by antenna manufacturers), as
> 28+8=36.
> 
> If you use an antenna with more than 8dBi of gain, you will just have
> to turn down the power in the router to stay within regulatory limits.
> I think the setting in OpenWRT / Commotion is in
> Advanced -> Network -> WiFi
> Then pick the Master interface and edit it, one of the sub-pages there
> will have something about output power. Set it to your dBm output, and
> you should be good to go!
> 
> One thing to keep in mind is that as the gain of an omnidirectional
> antenna goes up, the signal gets "squished" into a flat pancake around
> the antenna - there will be less signal that goes up and down at an
> angle around the antenna.
> Not a lot of gain:
> http://www.rf-kits.com/schematics/radpattern.gif
> A lot of gain:
> http://www.antennas-amplifiers.com/image/cache/data/Wireless2/OV/13/Dual
> OV13-3D-radiation-pattern-1000x1000.jpg
> 
> Do you need an omnidirectional signal? You can use much higher gain
> antennas if they are directional, if you are just trying to go further
> in a single direction, or in an area.
> 
> FYI - this is a good overview for folks in the USA:
> http://www.afar.net/tutorials/fcc-rules/
> 
> 
> 
> On 04/16/2015 02:49 AM, Marina Brown wrote:
>> Hi All:
> 
>> What is the top omni DBI i can use with a 600 MW Ubiquiti bullet 
>> without running into regulatory issues in the US ?
> 
>> --- Marina
> 
> 
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> 
> 
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-- 
Andy Gunn, Field Engineer
Open Technology Institute, New America
andygunn at opentechinstitute.org | 202-596-3484
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