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  Satellite Internet forum › Dish pointing and alignment › Formula for dB down off axis

Formula for dB down off axis

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chumleymobile
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Sep 13th, 2009 at 9:20pm  
Sirs/Ma'ams,

I've got the formula for dB down off axis for 3 db beamwidth ie (theta/3db beamwidth)^ x 12, anyone have the formula for dB down ref to 10 dB beamwidth? Many thanks.

Chumleymobile
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Admin1
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Reply #1 - Sep 14th, 2009 at 11:17pm  
You may try this beamwidth calculator but please be aware that the result is approximate.

The shape of the main beam is affected by the power illumination distribution across the dish.  The feed has higher gain towards the centre of the dish and lower gain towards the edge of the dish.  The effect is to greatly reduce the off-axis sidelobe levels with some limited on-axis gain reduction.   

Best regards, Eric.
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chumleymobile
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Reply #2 - Sep 15th, 2009 at 3:24pm  
Eric,

Good stuff, thanks.

Br's,

C'mobile
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Email me: eric@satsig.net

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