[amsat-bb] Fw: Re: More Clutter on 2.4 GHz

Tony Stone w4tas at gte.net
Mon Oct 9 13:58:01 PDT 2006

The part 15 rules for 2.4 GHz operation state that a maximum transmitter
output of 1 watt with a 6 dbi omni antenna is legal. This is 4 watts eirp.
With a directional antenna you must decrease your transmitter power
1 db below 1 watt for every 3 db antenna gain over 6 dbi.

Confusing as this may seem, it means that you can have 250 milliwatts
of transmitter output with a 24 dbi gain antenna. That is 18 db over
the original 6 dbi which is 6 units of 3 db each. This means that the
transmitter power must be reduced from 1 watt to 250 milliwatts (6db).

This is an effective isotropic radiated power of 64 watts and is perfictly

Check the gain of a 36 inch dish at 2.4 GHz and do the calculations to
see if it is legal or not.



----- Original Message ----- 
From: "Tony Langdon" <vk3jed at gmail.com>
To: "Nate Duehr" <nate at natetech.com>; "joseph Murray" <k0vty at juno.com>
Cc: <amsat-bb at amsat.org>
Sent: Monday, October 09, 2006 4:22 PM
Subject: [amsat-bb] Re: More Clutter on 2.4 GHz

> At 03:11 AM 10/10/2006, Nate Duehr wrote:
>>Also illegal.  Check the FCC's ERP limits for point-to-point 802.11 and
>>I believe you'll find that what your ISP did for you is breaking the law.
>>36" dish + 100 mW looks to me like it's way above the ISM band EIRP
>>limits for unlicensed use, since the limit is 100mW EIRP.
> Hmm, I thought your base EIRP was 4W (same as it is here) for 2.4 GHz
> wifi (and probably other SS/high speed data networking), and that
> under US rules, you could increase that further on point to point
> links on a sliding scale (we can't, it's 4W for all antenna
> configurations here).
> 73 de VK3JED
> http://vkradio.com
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