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Re: Idea for portable dish



The space between the dish sections may not be too critical on S band, but
they sure are on K band. I worked for a company that cut up dishes for use
at Ku band and the dish segment alignment was quite important. An easy way
to maintain proper dish geometry, is to make up and attach the joining
pieces BEFORE the dish is cut. Once the joining pieces are fabricated and
the holes drilled in the dish, you can safely cut it up. When the dish is
re-assembled, the pre-drilled joining pieces will maintain the proper gap
between the sections.  The other problem is dish distortion. The shape of
the dish is maintained by the memory effect of the stressed material. When
the dish is cut, the stress across the surface changes and may or may not
affect the final shape. It's not that cutting up a dish and re-assembling it
won't work, it will. It's just a matter of how much gain you want to retain.

Howie, AB2S
----- Original Message -----
From: "Stan" <stan@capecod.com>
To: "William Leijenaar" <pe1rah@yahoo.com>
Cc: <amsat-bb@AMSAT.Org>
Sent: Friday, October 12, 2001 9:04 AM
Subject: Re: [amsat-bb] Idea for portable dish


> Hello William,
>
> Take a solid dish and cut it up with a metal cutting saw.
>
> Label all parts to indicate how they will be re-assembled.
>
> alternative #1: cut into pie shaped sectors and splice together with
> small plates at the joints.
>
> Alternative #2: cut the center out, then cut the outer ring into
> equal sectors, splice with metal plates at the joints.
>
> after assembly, the small gaps between dish sectors do not
> significantly effect the dish performance.
>
> Metal plates would use 4 screws, with heads flush mounted and
> countersunk to minimize dish working surface distortions.
>
> I had a 4' dish like this, but heavy winds blew it off the tower
> and it was no longer a parabaloid, after the impact.
>
> Stan, WA1ECF
>
>
>
> William Leijenaar wrote:
> >
> > Hello satellite amateurs,
> >
> > I am looking for some idea to make an portable dish
> > for use at 13cm (AO40 RX). The design must be light
> > and an little package for transportation. It must be
> > possible to put it inside my back-pack, so I can also
> > be qrv via AO40 on my next holliday trip :-)
> >
> > I have some idea of an umbrella-alike principle.
> > The problem is only to find an RF reflecting material,
> > that can be foulded or packed very little.
> > I know there exists some kind of "aluminium cloths",
> > that is used for medical use to warm up under-cooled
> > people. When such material works, then it must be
> > possible to make an dish that can be very easy to
> > transport and can be very light weight.
> >
> > Maybe somebody knows if this material can be used as
> > dish RF reflector ? And if it is physical strong
> > enough ?
> >
> > Other ideas are also welkom...
> >
> > 73 de PE1RAH, William
> >
> >
> >
> > __________________________________________________
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