Re: FW: [amsat-bb] Lock on Tracking

["Edward R. Cole" <al7eb@xxxxxxxxxxxxx>]

At 03:20 PM 12/11/2002 +0000, Rod Smallwood wrote:

>Sounds good but I don't think AO40 would look for me
>I think I would have to look for it! 
>
>Having thought a bit more about it you could do it in 
>hardware if you had four antennas and four receivers (or one
>muxed around the four antennas). Another possibility
>would be to have four feeds at different angles to
>the dish. And finally there's the flat phased array
>which is steered electronically. (anybody know how?)
>
>Rod G8DGR
 
Rod,

You brought up an idea that I have speculated about a little:  Phased-array
antennas.
To stear them they usually use adjustable delay lines (which I'm not an
expert on).

But why I replied is sort of off topic.  I think a flat array of phased
patch antennas might be the answer for a portable microwave antenna (for
AO-40 reception, or general microwave roving).  I haven't played with
patches, yet, but I think they average about 10 dB gain.  To receive AO-40
on 2401 you should strive to have a minimum of 24 dBic gain (roughly the
gain of a 3-foot dish).  

A square patch array of 16 patches would produce 22 dB gain (4x4 array).
But perhaps a rectangular (4x8 array) would be better, achieving a ideal
gain of 25 dB.  In the actual array I suspect there would be a couple dB
phasing line loss involved.  The easiest would be a set of rigid panels of
patches the would snap together once you were at your portable location.
They would break-down into a small package of flat squares (two-sided pcb?)
that would pack easily.  Another approach would be metalized flexible
plastic, etched into the array of patches and connecting stripline.  Just
roll up the antenna and stuff into a shipping tube.

Now I wonder who will be first to make one?

Ed - AL7EB
PS: the tricky part is designing the stripline phasing system.
  

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