Path: utzoo!utgpu!water!watmath!clyde!rutgers!sri-spam!ames!lll-lcc!well!shf
From: shf@well.UUCP (Stuart H. Ferguson)
Newsgroups: comp.sys.amiga
Subject: Re: dish formula
Message-ID: <5083@well.UUCP>
Date: 27 Jan 88 01:53:15 GMT
References: <2252@gryphon.CTS.COM>
Reply-To: shf@well.UUCP (Stuart H. Ferguson)
Organization: The Blue Planet
Lines: 27

In article <2252@gryphon.CTS.COM> mjb@pnet02.cts.com (Martin Brown) writes:
>I was working on a space station picture in Sculpt 3D, and in particular, a
>parabolic dish antenna, which led me to wonder just how the parabolic formula
>is derived for a particular dish. Is it a matter of frequency? distance to
>source? both? Anybody familar with this stuff? Help and examples would be
>appreciated! Thanx!
>                          - Martin Brown -

I'm no expert, but I think that many so-called "parabolic" reflectors are 
aproximated by a piece of sphere.  For very flat dishes such as you might find
on spacecraft, the aproximation works reasonably well and the spherical
segments are much easier to construct than their parabolic siblings.  (This is
true in real life as well as Sculpt-3D :-).  The position
of the focus changes slightly as a function of wavelength (chromatic abberation
I believe it's called), but normally the focus is one-half radius from the
center of the dish.

>UUCP: {ihnp4!scgvaxd!cadovax rutgers!marque}!gryphon!pnet02!mjb
>INET: mjb@pnet02.cts.com

This and other useless and often incorrect information can be found in the
mind of ...


-- 
		Stuart Ferguson		(shf@well.UUCP)
		Action by HAVOC		(shf@Solar.Stanford.EDU)