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Reply To: Microcell Antenna Heigth

#49716
pix
Guest

Hello Abdel,

You came to the right conclusions, but you got some facts a little bit wrong. I hope you don’t mind if I explain the “why” and “how” of your previous post ? It might of some help for other readers…

The mechanical tilt doesn’t provok “bouncing” of the waves on the ground to the right and left : when you downtilt an antenna, you actually downtilt the front lobe.
The problem comes from the side lobes and back lobe.

You can imagine an antenna as a torchlight that sends light
– from the front a lot
– from the back a little
– from the left and right sides a little

When you tilt the torchlight’s front, there is an uptilt of the backlobe and there is no tilt of the side lobes.

Backlobe is bad, because it will transmit your frequencies in the opposite direction, creating interferences with other BTS using this frequency.

Sidelobe is “usually” less critical, but in your case… it is critical. The side coverage might go too far.

So yes, I agree with you : choose an electrical tilt if available, but there are strong chances that this kind of big aperture antenna do not have electrical tilt.
Anyway, electrical tilt can’t go further than 14°, as far as i know.

Second point :
an antenna is designed in such a way that
1. high-gain antennas have narrow vertical aperture
2. low-gain antennas have wide vertical aperture

But this is fixed ! you cannot change the gain of an antenna by yourself. I you reduce the BTS power, you don’t reduce the gain of the antenna. The antenna gain will still be xx dBi, and the aperture will still be 55°.

In my opinion, drop the installation of this site : you’re going to implement a microcell with the coverage of a macrocell… it’s going to bug your optimization for years 🙂

Can’t you buy a small outdoor antenna you could install on a vertical wall, at 3 meters high ?

-Pix