[Commotion-discuss] antenna dbi

[Andy Gunn]

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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
> 
> 
> _______________________________________________ Commotion-discuss
> mailing list Commotion-discuss at lists.chambana.net 
> https://lists.chambana.net/mailman/listinfo/commotion-discuss
> 

- -- 
Andy Gunn, Field Engineer
Open Technology Institute, New America
andygunn at opentechinstitute.org | 202-596-3484
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