Newsgroups: sci.engr.electrical.compliance
Subject: Re: Wireless networks & regs...
References: 
Matt Wilson  writes:

> People appear to be getting keen to extend wireless networking to cover 
> larger areas or to set up point to point links between buildings say.  
> 
> All well and good but presumably although the 2.4Ghz band is unlicensed you 
> can't go upping the power or building Yagis etc to add gain.  Or can you?  
> (An Amateur licence might cover it I suppose).
> 
> Any thoughts on this welcome so I can pass the advice on.

The usage of 2.4 GHz is unlicensed with certain limitations. 
This means the limitations of allowed transmitting power 
and/or antenna field strength. 

This means that that in most countries you can't 
just add power to the system. You need to stay within
the prefefined power limits set by the radio authorities. 
The power of typical WLAN card in Europe is in below 100 mW.

What kind of antennas and how you are added coudl vary between 
countries as well. For example in Finland the situation is 
the following:

The signal strength form antenna is defined to be allowed the same 
as the maximum allowed power level (100 mW) applies to 
omni-directional antenna. 
So if you use more directional antenna with more gain 
to certain direction than omnidirectional has, you 
are allowed to put in less power than the normal maximum power. 
How much power is allowed depends on the antenna gain. 
So if you attach more antenna here, you need to have some 
technical information available (WLAN card power output level, 
antenna gain figure and antenna cable attanuation) and do 
some calculations to see if your system is operating within the 
limits set by authorities (it is a good idea to keep the 
technical data and calculations stored, in case you need to 
prove the authorities your system meets the regulations).
If I remeber right, those limitations were only for transmitting, 
so you can use whatever antenna you want, if you use it only 
for reception of the signal. 


I don't knwo the actual rules in other countries. 





-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/