Subject: [NEXTEL-1] Re: Antennas on water towers:new question.

From: Marcel <[email-masked]>
Date: Wed, 08 Jan 2003 11:41:35 -0500

------- Original Message --------
From: "Peter Moncure" <[email-masked]>
Subject: Re: Antennas on water towers:new question.

> Picture a Cylindrical water tank with cellular and pcs sector antennas
> on all sides of it.  How could this effect a VHF or UHF dipole on the top
> of it?  Would adding sectored microwave (ISM) or some higher powered point
to
> point microwave to it effect the VHF/UHF signals?  What do you think could
> be done to make a system like this work?
Sorry about last msg, meant to reply with more than a blank stare!  There
appear to be a number of questions lurking in that post:
1) Will having other physical antennae nearby be a problem?  Since by your
post I assume they aren't visible in the near field aperture, No.
2) Will the RF from the other antennae cause trouble?  Probably not.  If
you're the lowest frequency on the tree, you will more likely cause than
receive harmonic interference.
3) Will the RF from the other antennae cause intermodulation interference?
This is trickier, since (for example) two microwave carriers might
conceivably be a VHF receive frequency apart, and that can be nasty.  I have
yet to see a reliable IM model for conditions like those you describe--it's
nuts when you don't know the actual frequencies in use, only a large band
within which they might lie.
4) Will they raise the noise floor?  Yes, but by how much?  This depends on
lots of factors.  Quality of Tx, good installation practices &c.
5) Will the top edges of the cylinder offer some shielding against 3 and 4?
Yes, but most of those services probably have antennae which are already
aimed out, so not much.  Still, it would probably be better than, say, the
same vertical distance sidemounted on a tower.

Hope this helps.

Peter Moncure, VP RadioSoft
386.426.2521, FAX 386.423.0821
"Whatever it is, we can model it faster and better"

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