[Commotion-discuss] antenna dbi

Tue Apr 21 15:25:57 EDT 2015

The Bullet M5-HP has max 25dBm (aka ~300mW) output power while the M2-HP
has max 28dBm (aka ~600mW), at least according to UBNT datasheet.

If the OP is referring to an M2, my advice would be to not use such a high
power radio in 2.4GHz if you're wanting wifi clients to connect directly to
it.  Setting very high TX power can saturate the receiver and drown out
lower-power and/or distant clients.  Similarly, using a high-gain (aka
highly directional) antenna greatly limits the beam width over which
clients could connect.  Something like a Nanostation M2 or Picostation M2
would be better suited for direct 2.4GHz client access.

Also, long-distance 2.4GHz links, especially in urban areas, are barely
viable these days.  A bullet M5 would likely work much better for any
high-power/long-distance use.

Either way, OpenWRT should include some tx power limits per the country
code you set.  For example, a Bullet M5 running AA r42647 with country code
US will give this in response to "iw phy0 info":

        Frequencies:
            * 5180 MHz [36] (17.0 dBm)
            * 5200 MHz [40] (17.0 dBm)
            * 5220 MHz [44] (17.0 dBm)
            * 5240 MHz [48] (17.0 dBm)
            * 5260 MHz [52] (23.0 dBm) (no IR, radar detection)
              DFS state: usable (for 291882 sec)
            * 5280 MHz [56] (23.0 dBm) (no IR, radar detection)
              DFS state: usable (for 291882 sec)
            * 5300 MHz [60] (23.0 dBm) (no IR, radar detection)
              DFS state: usable (for 291882 sec)
            * 5320 MHz [64] (23.0 dBm) (no IR, radar detection)
              DFS state: usable (for 291882 sec)
...
            * 5745 MHz [149] (30.0 dBm)
            * 5765 MHz [153] (30.0 dBm)
            * 5785 MHz [157] (30.0 dBm)
            * 5805 MHz [161] (30.0 dBm)
            * 5825 MHz [165] (30.0 dBm)

Also, this page provides some handy antenna gain limits w/r/t to max
permitted EIRP in the ISM bands.  For example, a 2.4GHz radio with 28dBm
output could only use an antenna with max 12dBi gain.

http://www.wisp-router.com/page.php?11

On Thu, Apr 16, 2015 at 5:41 AM, Adam Steele <adamrobertsteele at gmail.com>
wrote:

> What frequency is your Bullet made for? EIRP limits vary between bands.
>
> Adam
> On Apr 16, 2015 2:49 AM, "Marina Brown" <catskillmarina at gmail.com> wrote:
>
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>>
>> 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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>> -----END PGP SIGNATURE-----
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-- 
Ben West
http://gowasabi.net
ben at gowasabi.net
314-246-9434
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