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Re: "Trash Can" or steel drum dish antennas



Ah, such is life! My hobby job (what I do to support my hobby!) is as a
technician at the Andover, Maine satellite earth station which, as many of
you know, was one of the first international satellite stations in the
world. It was originally called Telstar.

Andover-01 was the "horn" antenna here but, when the facilities were sold to
MCI the dish was diassembled and the Radome was dismantled. It was expensive
to keep it heated and inflated and the other antennas (30m+) had as much or
more gain. The antenna was sold for scrap before I came back in '91.

To my knowledge there are a couple more of these in Europe (France and
Italy?) but not the US...

----- Original Message -----
From: Scott Townley <nx7u@mindspring.com>
To: <n7bfs@qwest.net>
Cc: <T5z4@aol.com>; <RMckni8527@aol.com>; <amsat-bb@AMSAT.Org>
Sent: Tuesday, December 04, 2001 6:05 AM
Subject: Re: [amsat-bb] "Trash Can" or steel drum dish antennas


> So far there are two votes for "high performance dishes".  Those votes
> are correct!
> BUT...the shrouding is accomplished by a "drum" or cylindrical surface
> that is covered in *microwave absorbing material*.
> At 2GHz this stuff is *heavy*.  Not impossible but a bit tricky.
> As to performance, it both 1. reduces spillover from the feed and 2.
> edge diffraction from the rim of the reflector.  Resultant antennas meet
> FCC Part 101 "category A" requirements for radiation pattern.  This is
> something like -50dB sidelobes and a front-to-back of more than 65dB
> (not sure of the precise numbers, but they are ridiculously small!).
> So...for satellite work they would be the cat's meow; Tsys nearly just
> that of cold sky and the receive preamp.  Just a bit bulky (and not sure
> where one would get the microwave absorbing material; Cuming Corp. used
> to/still does(?) make a product called EccoSorb which is what you'd
> want).
>
> As an aside, anyone ever heard of a "cornucopia" antenna?  Some of the
> old long-haul analog microwave sites run by the old AT&T still have some
> up.  They are generally a cone pointing up with an "elbow" opening that
> opens to the horizon.  Those have even better sidelobe/backlobe
> performance.  I have some pictures in old textbooks; they appear to be
> one of the original radio astronomy antennas.  And now they're all dark;
> someone needs to pull one down and fire it up!!
>
> Douglas Cole wrote:
> >
> > On Monday 03 December 2001 13:48, T5z4@aol.com wrote:
> > > In a message dated 12/3/01 4:04:10 PM Eastern Standard Time,
> > > RMckni8527@aol.com writes:
> > >
> > > <<  They do actually look like a trash can, or maybe more
> > >  closely resemble a tub used for icing down a beer keg.  >>
> > >
> > > I wonder if a steel drum like those in the islands could be fashioned
to
> > > work well without the hammered out musically tuned zones on it's
surface.
> >
> > Well what I see described fits what we call a "hi-performance" dish
shroud
> > for most of our 6GHz ( actually 5.6 to 5.8 ) paths ( ds3 radios running
> > telephone and public safety traffic ) , and ours are 2 and 3m dishes so
I can
> > tell you  from experience that those shrouds ( trash can sides ) are
pretty
> > large and heavy , but they work very well when you have local paths that
are
> > not in the same line as your path , but are close enough nearby
 proximity )
> > to be a problem without the shroud and are required with some licenses .
> >
> > With that said the only thing I can think that a shroud would do for us
round
> > dish owners on S-band would be to reduce the terrestrial noise
 microwave
> > ovens etc ) , anyone know better on this please correct me , since I
have
> > been thinking about building my own "hi-performance" shroud for my 60cm
dish
> > to see how it would help my local noise .......
> >
> > What do the "experts" have to say ?
> >
> > --
> > Douglas Cole N7BFS
> > AMSAT#26182
> > http://www.users.qwest.net/~cdoug3
> > ----
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>
> ----
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