[MLB-WIRELESS] kerrazy antenna question

[Julian Featherston]

> -----Original Message-----
> From: Clae [mailto:clae13 at yahoo.com] 
> Sent: Tuesday, 19 February 2002 2:33 AM
> To: melbwireless at wireless.org.au
> Subject: [MLB-WIRELESS] kerrazy antenna question
> 
> 
> HI all,
> 
> I'm wondering whether this is possible:  if you are using a parabolic 
> dish, would moving the actual transmitter bit (there's that darn 
> terminology thing again) back and forth across the focal point of the 
> dish allow you to adjust the beam shape from narrow to wide and back 
> again?
> 

My understanding is that moving the feed point (or feed antenna) in and
out will just result in less gain.

But moving the feed point a little to the side will bend the beam in the
opposite direction, with little loss of signal.
If the feeds are small enough so as to not block much signal one can
have multiple divergent beams emanating from one dish. These guys
suggest 15º off boresight is possible, somebody else suggested 12º
http://global-cm.net/antennas/multifeed.html

The CSIRO have just started marketing an antenna that doesn't focus to a
point, but to a surface. This allows up to 19 divergent beams from one
antenna!!! But you must have 19 targets in within roughly 38º
They designed it a long time ago, but say they had to wait until there
was sufficient density of satellites.
http://www.tip.csiro.au/ICT/SpaceSatellite/Multibeam1.htm and they are
talking about cheap wireless data too
http://www.tip.csiro.au/ICT/Broadband/index.htm


Jules
 


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