[amsat-bb] Re: big dish

[Anthony Monteiro <aa2tx@xxxxxxxxxxx>]

At 11:38 PM 10/17/2006, w7lrd@comcast.net wrote:

>Hello
>I have this 12 foot dish waiting for "something".  I want a dual L/S 
>dish system.  Given the beamwidth of a 12 footer would be 
>small.  What would happen if the feed were placed at a spot other 
>than the focal point?  I realize  I would be  not using the dish to 
>it's full potential.  Would that broaden the beam width?  I also 
>have a four footer which would be more applicable.  I am planning 
>for the next HEO and retirement in six months.
>73 Bob W7LRD
>Seattle

Hi Bob,

All you have to do is under-illuminate the dish. Use
a beamwidth on your feed that is smaller than the
dish diamter. For example, if your feed only illuminates a
5-foot diameter part of your 12-foot dish, then the
beamwidth (and gain) on your dish will be like a 5-foot dish.

73,
Tony AA2TX

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