[MLB-WIRELESS] kerrazy antenna question

[Julian Featherston]

> -----Original Message-----
> From: Hamish Moffatt [mailto:hamish at cloud.net.au] 
> Sent: Tuesday, 19 February 2002 8:21 AM
> To: melbwireless at wireless.org.au
> Subject: Re: [MLB-WIRELESS] kerrazy antenna question
> 
> 
> On Tue, Feb 19, 2002 at 04:24:39AM +1100, Julian Featherston wrote:
> > My understanding is that moving the feed point (or feed antenna) in 
> > and out will just result in less gain.
> 
> Less gain should mean more beamwidth. After all, you get more 
> gain by sacrificing beamwidth.
> 

Too true, beamwidth will change.
However, the dominant effect is phase shift resulting from a difference
in path length.
When positioned inside the focus, the paths are shorter for beams
reflecting from the centre of the dish.
So if one wants a "widebeam" dish it seams best to go for multiple
(small or offset) feeds.


Jules


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