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alialiraqi
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real angle for 90 degrees sector antenna and overlapping

Sun Mar 09, 2014 12:34 pm

hello


I am setting a wisp PTMP system . trying to reach customers who are in distance of 1-6 kilomters from my tower.


and will use this antenna

http://www.wireless-instruments.com/en/ ... -17hv.html


I thought that is is good to make an overlapping angle between the sectors for the following reasons:

1- to improve the signal by limmiting the angle of coverage of the antenna to the angle which the signal can be recieved by its full gain. ( whereas the signal at the ends of the angle is very low)

2- to make an alternative solution for the CPE to recieve one of the signals of the two overlapping sectors.


built on the fact that the antenna's official angle of horizontal coverage is 90 degrees.
what is your advice for the overlapping angle that can be done between the sectors.

which angle I will plan for each sector instead of its original 90 degrees.


thanks in advance
 
pteek
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Re: real angle for 90 degrees sector antenna and overlapping

Sun Mar 09, 2014 5:45 pm

I don't think you should overlap two adjacent sectors since from the CPE's point of view, one sector will always be pure noise. Unless both the sectors are separated by a window of 10MHz or higher.

Then it may help you do what you are saying in 2.

About 1, the signals from two sectors won't add up unless they are exactly same. Even if they are same, which they should not be, it will only cause problems.
 
n21roadie
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Re: real angle for 90 degrees sector antenna and overlapping

Sun Mar 09, 2014 9:28 pm

From the datasheet the +/- 90º has -5db, so for a effective overlap antennas should be positioned 60º apart and not 90º
 
pteek
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Re: real angle for 90 degrees sector antenna and overlapping

Mon Mar 10, 2014 9:22 am

@n21roadie

Can you elaborate on this please?
 
n21roadie
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Re: real angle for 90 degrees sector antenna and overlapping

Mon Mar 10, 2014 2:08 pm

Sorry typo - should have been +/- 45º from 0º that signal level drops to -5db, and not +/- 90º?
It used to be -3db signal level for axis beamwidth but manufacturers now use -6db or even -12db,
so it's important to check if you read Beamwidth Horizontal 90° what exactly on the graphs is the -db level at those points
 
ste
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Re: real angle for 90 degrees sector antenna and overlapping

Mon Mar 10, 2014 3:54 pm

I guess the misunderstanding here is that Sector Antennas never stop at a given angle.
A 90 Degree sector is what the vendor believes it is made for but at -46 or +46 Degree it is still sending.

Every Sector overlaps.

Normaly a vendors angle is calculated so that at the edges of the sector you've -3db tx-power (=half the power).
A 60 Degree Sector with 16dbi has 13dbi at -30/+30 Degree and 16 at the center. Some vendors use -6db.

Look at the antenna patterns what happens exactly at what angle.

In most cases customers around a tower are not evenly spaced so just putting up 4x90 Degree Sectors is no good
idea at most sites.

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