In some places, like the U.S., there are different EIRP limits for
point-to-point and point-to-multipoint links. Also, as you mention,
a high-gain antenna will reject noise from the sides and behind.

Dave

On Mon, Jan 06, 2003 at 11:48:23AM -0800, Henry B. Hotz wrote:
> At 8:17 AM +0100 1/2/03, Pavel Cahyna wrote:
> >In our country we have a regulation dictating that a wireless device
> >like this shall look from any direction like an isotropic source of
> >radiation with total power not exceeding ... (some value that I don't
> >remember; 100 mW maybe?) so if we focus the output by means of a
> >parabollic antenna, we must lower the power accordingly.
> 
> I'm not up on regulations, but if the restriction is on EIRP (as it 
> sounds) then  once you get to an antenna that requires you to reduce 
> your output you have nothing to gain by using a better antenna.
> 
> In other words I think this only makes sense if 1) you don't have 
> enough power though your standard antenna to reach the regulatory 
> limit, or 2) you don't actually intend to adhere strictly to the 
> regulation, or 3) you have some nearby interference which the 
> regulations don't prevent (like bluetooth, or a cordless phone).
> 
> I'm not an expert, but I hope you're not barking up the wrong tree here.
> -- 
> The opinions expressed in this message are mine,
> not those of Caltech, JPL, NASA, or the US Government.
> Henry.B.Hotz@jpl.nasa.gov, or hbhotz@oxy.edu

-- 
David Young             OJC Technologies
dyoung@ojctech.com      Engineering from the Right Brain
                        Urbana, IL * (217) 278-3933