Re: Cassegrain??? -- The Astra 2D Forum

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Subject: Re: Cassegrain???

Author:
Outsider

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Date Posted: 06:03:36 11/14/03 Fri
In reply to: Ingemar 's message, "Cassegrain???" on 11:22:31 11/13/03 Thu

>Can someone please help me?
>
>If I have understand everything correctly is
>cassegrain a satellite dish with a LNB in the center
>and this technique makes the dish more effective.
>
>I will not be allowed to have a larger dish than 1,2 m
>in the garden. Could a 1,2 m cassegrain dish replace a
>larger "normal dish"?
>

Small, symmetric Cassegrain antenna is not so good idea: the subreflector must have some minimum size (several wavelengths) and then it will cause remarkable blockage in a small dish. There are Gregorian (like Cassegrain but different form of subreflector) offset dishes and some of those are very good. But anyway, 10% more efficiency is just 10% bigger dish area, about 5% bigger dish diameter, it seldom solves the problem, and you really cannot expect more if you replace a good dish with an excellent one!

There's no replacement of a big dish! :(

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