antenna height

[mohammed Gh.]

can I deign antenna height 3 meters above the roof ? if not why I cant?

FYI
technology is WiMax, Band =2.3GHz


thanks in advance

[electron]

Hi,


It depend how much us distance of building EDGE from button of antenna .


Cheers

can I deign antenna height 3 meters above the roof ? if not why I cant?

FYI
technology is WiMax, Band =2.3GHz


thanks in advance

[Optimustron]

Some time ago I made a drawing to show to new people how to get a better idea of how much you need to put over the roof the center of the antenna as a function of distance from edge of the building, is simple and is based on the point of -3 dB for antenna beamwidth, however if you have a high directivity you need to consider another point because of high reflexion on the roof of the building, is better to place the antennas at the edge but if you need to hide the antenna you need put a levele higher from the roof, here is the drawing and excuse me for the spanish but is part of my tesis and I only change some words to english because is late here and I need to go sleep, maybe I will change that image another day. By the way Altura=Height, Distancia a la orilla=Distance to edge.

Distance to edge.jpg

I hope this can clarify something the idea, best regards friend,

[s.saadhassan]

For antenna height, there are 2 main considerations:

1. The antenna height should be enough to clear the clutter and have good propagation. Generally antenna height should be at least twice the average clutter height.
2. There should be no near field obstacle. Same building roof shadowing, nearby buildings/objects blocking the 3dB beam must be avoided. Minor obstacles like other towers etc should not be blocking more than 5% of beam.

So installing 3m above rooftop is fine if above 2 criterias are met i.e., no nearby obstacle and the building being high enough to be well above average clutter.

Hope that helped.

[mohammed Gh.]

For antenna height, there are 2 main considerations:

1. The antenna height should be enough to clear the clutter and have good propagation. Generally antenna height should be at least twice the average clutter height.
2. There should be no near field obstacle. Same building roof shadowing, nearby buildings/objects blocking the 3dB beam must be avoided. Minor obstacles like other towers etc should not be blocking more than 5% of beam.

So installing 3m above rooftop is fine if above 2 criterias are met i.e., no nearby obstacle and the building being high enough to be well above average clutter.

Hope that helped.

thanks s.saadhassan for this information
my case is when I put the pole at edge of building , in this case the issues of roof was solved. right?
at the same time I have an obstacle, the obstacle height is two meter above the selected roof and far about 10 meter from the edge of building.
how can deal with this design ?
please guide me to solve this case
thanks again

[s.saadhassan]

Yes. Roof clearance should be fine.

For the obstacle, it depends how big the obstacle is. If it is narrow like another tower or penthouse of nearby building then you can try changing the azimuths to put the obstacle in the null. If obstacle is very narrow like a monopole tower then its blocking less than 5% beamwidth and will create no issue in any case.

However, if the obstacle is very wide and blocks some intended coverage area, then you need to increase antenna height or change location (if possible).

[mohammed Gh.]

Yes. Roof clearance should be fine.

For the obstacle, it depends how big the obstacle is. If it is narrow like another tower or penthouse of nearby building then you can try changing the azimuths to put the obstacle in the null. If obstacle is very narrow like a monopole tower then its blocking less than 5% beamwidth and will create no issue in any case.

However, if the obstacle is very wide and blocks some intended coverage area, then you need to increase antenna height or change location (if possible).

thanks
how many meters I have to increase above the obstacle height in general?

[s.saadhassan]

In general, I would like the antenna to be at least 5m higher than the obstacle.

Note that if the area behind the obstacle is not dense (e.g., a park etc), then even 2m clearance will be fine (just to clear the main beam above the obstacle and not considering impact of its shadow)..