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RE: Offset Dish Antenna Aiming
- Subject: RE: [amsat-bb] Offset Dish Antenna Aiming
- From: "Frederick M. Spinner" <fspinner@xxxxxxxxxxx>
- Date: Tue, 30 Jul 2002 16:17:10 +0000
Long Answer: NO
A offset-fed parabola is literally a cut out section of a larger center-fed
parabola... so the shapes are completely different.
That is why the "effective" f/d is 0.7 when the real f/d of the larger
parabola is 0.3...
Fred W0FMS
>From: "Edward R. Cole" <al7eb@ptialaska.net>
>To: "Reicher, James" <JReicher@hrblock.com>, "'Frederick M. Spinner'"
><fspinner@hotmail.com>, amsat-bb@AMSAT.Org
>Subject: RE: [amsat-bb] Offset Dish Antenna Aiming
>Date: Thu, 25 Jul 2002 16:32:32 -0800
>
>
>
>At 12:59 PM 7/25/02 -0500, Reicher, James wrote:
> >
> > Fred, this may sound like a dumb question, but would the off-set dishes
>work
> > correctly if they were modified to NOT be offset?
> >
> > 73 de N8AU, Jim in Raymore, MO
>
>
>Jim,
>
>Short answer --- NO. They are designed for the feed to be at particular
>spot. This is the focal point for offset dishes. Its just like placing
>the
>feed on a center-fed dish in the wrong spot...doesn't work! Its all in the
>mathematics of the surface shape.
>
>He he...you could run over them with a car to modify them, but kind of
>think
>that would make them not work too well!
>
>
>
>
>----
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