SatSig topic:

How to find focal length for LNB

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Jan 26^th, 2024 at 4:30pm

Hi
I need help in determining the focal length of my offset antenna.
I have an antenna where the arm on the LNB is not done correctly and is not in the centre of the focal length.
Currently, in order to watch TV somehow, I have to find the best place for the LNB by "eye" using a satmeter and a string to fitted.
I would like to do it properly, using the rods screwed to the antenna and the arm with the LNB.
Hence my question, how do I calculate the focal length, where exactly should the LNB be?

The dimensions of the dish:
89cmx81cm
The deepest spot is 6,5cm
Thank you

May 1^st, 2026 at 7:52pm

You could try the calculator at:

https://www.satsig.net/pointing/finding-dish-offset-angle.htm

You need the maximum depth of the dish as well as the two diameters. Put an accurately straight edge up/down the front, and measure the maximum depth as accurately as possible.

It it works let us know. The calculation method is a bit uncertain and it would be helpful to get feedback.
wxw