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Terry

8dbi patch

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Has anyone got a diagram, graf or table that shows a typical 8dbi patch radiation patern?

I want to know how much signal is lost as you move out from the centre of the beam. If 0deg is 100%, what is 10deg and 20deg and so on ?

I am also interested in seeing the same info head on so it looks like a set of rings.

Can anyone help ?

Many thanks, Terry

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I find that sort of thing hard to follow, how do I work out the reduction in range at say 20deg off centre (left or right) ?

I would also like to know how much more reduction there is if you then go 20deg off centre vertically as well ?

I suppose a 3d diagram would help or a diagram with multi plots in 1dbi steps or simular.

Terry

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At 20° left/right you will be approx -2dB down from max gain. If you also are 20° off axis vertically, then tally another -1dB (approx) loss.

The antenna's vertical and horizontal beamwidth spec reflects the -3dB (half power) crossing points (the blue colored circle in the linked beam plots). Most folks are under the impression that the signal stops there. But, these are not brick walls and useful signals continue for many more degrees. Even the antenna's backside has active fish fin regions that are only -10dB down from max gain. But the deep null areas are indeed dead zones in practice.

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http://www.rcgroups.com/forums/showpost.ph...112&postcount=5

You had even posted on that thread BTW...

The angle is written on the outside of the diagram, so for reduction at 20° right you'll take the horizontal graph, look where the curve is at 20° right (340°), and you'll see it's roughly at -1dB (the dB circles are a log scale). Knowing range is doubled every 6dB you can calculate the reduction easily. Horizontal and vertical effects are summed.

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Thats a good post Kilrah !

I understood the 3db plot but found it hard to understand what it realy ment in practice.

The reason I asked is because I am trying to make plans for a new video receiving system that I have in mind. If all goes to plan it will be a significant improvment on my current 4 way diversity system. I won't say too much yet but it draws experience from both my 4 way diversity system and my auto tracking aerial.....

Terry

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