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

Nate Duehr nate at natetech.com
Mon Oct 9 10:11:23 PDT 2006

joseph Murray wrote:
> Maybe I should put a couple of pence into this for what ever it's worth
> For  the last four years I have had my ISP hook up via 2.4 gHz 
> A Cisco 350 system over a 15 mile connect at 100 mw.
> Weather has not been a factor.
> I use a 36 inch vertically polarized dish .
> 50 feet of LMR 400 coax to the Cisco transceiver.
> This is possible because the dish looks down a water shed where the fall
> off 
> is equal to at least 3 feet per mile.
> That makes trees disappear so to speak.
> All of this might be a bit unusual , but it is possible.

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.

(I seem to recall seeing that there was a higher limit for 
point-to-point, but a 36" dish is going to be enough gain it's going to 
blow that limit out of the water too.)

But since there's plenty of very public documentation of lots of people 
doing this, it's obvious the FCC simply doesn't give a damn, or they'd 
be hunting the web and mailing lists for all the people bragging about 
their link distances and mailing out Enforcement Action letters.


Consider your own setup there just more proof positive that (here in the 
U.S. at least) the 2.4 ISM band is just a free-for-all that the 
regulators really don't care about.

By the way, your ISP probably *could* have done that shot legally up at 
5.8 GHz with Motorola Canopy or Trango Wireless gear.  They get a limit 
of a full watt EIRP up there.  Might have even gotten away with it at 
5.3 GHz where they get a 200 mW EIRP limit.

Nate WY0X

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