[MLB-WIRELESS] RF noise reduction

John Dalton john.dalton at bigfoot.com
Wed Feb 19 18:22:42 EST 2003

> Instead of trying to get around this by getting a higher gain antenna 
> (which then creates noise further away for someone else)

Directional antennas don't necessarily create noise for others
further away.  The correct thing to do is increase the gain (directionality)
of your antenna AND wind the transmitted power back so the EIRP is the same as it
was before you added the directional antenna.

> if I can get a 
> link up with an 8db omni, the link is say East of me, am I going to screw 
> up my reception if I surround the north/south/west sides of the antenna 
> with something RF absorbing (I'm thinking a plastic of some sort).

What you have just described will have a similar radiation pattern to a
directional antenna with the power reduced to maintain EIRP at a
constant value (described above).  The difference is that by using absorbers
you are wasting most of your power as heat.  If you replace your absorbers
with reflectors in an effort to conserve power, you have a (drum roll please)...
directional antenna!

> I know you'd be covering a smaller area but if it worked then it would be 
> possible to put an extra device in and use the same frequency (useful for 
> sites with good LOS and multiple links).

This is known as antenna segmentation.

All good ideas based on good reasoning, just that someone has
already been there!  Seriously, don't give up on coming up with
ideas like this.  It's the nature of research that most ideas
have already been thought of.  When you happen to come up with
something no-one has already thought of you have a breakthrough.


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