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Dish antenna Prime-focus technical basics
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#1
Here is a small introduction to the technical specifications that one may come across while building a parabolic satellite dish antenna.

The first thing that is common is f/D ratio which is the focal length f of the dish reflector divided by the diameter D of the dish.
Commercially available dish antennas have a f/D ratio of between 0.36 to 0.40 although 0.5 is also seen in imported antennas.
I prefer 0.38 for optimum signal reception.

Image 1 - The parameters of the satellite dish antenna indicated:
[Image: iPBoLJ8UdIg1A.jpg]

Image 2 - The dish antenna focussed properly with correct f/D ratio:
[Image: i625DDpwMBaK7.jpg]

Image 3 - f/D ratio is high leading to bad reception:
[Image: iba92bPll3GsRV.jpg]

Image 4 - f/D ratio is low leading to bad reception:
[Image: ibvUEcCfTpfnWY.jpg]
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#2
What is the significance of depth 'd'. How does it effect ?
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#3
(02-23-2013, 12:40 PM)samanth Wrote: What is the significance of depth 'd'. How does it effect ?

The depth 'd' is the depth of the parabolic reflector.

The depth 'd' also has effect on the signal reception. The deeper the dish, the focal length will also reduce and the LNB will see less of the dish reflector giving low signals impacting normal reception.

On the other hand, if the dish is shallower, focal length will increase and the LNB will see more of the dish reflector picking stray signals, noise from the dish reflector impacting normal reception.
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#4
plz give more details about y=x^2/4f
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