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## Re: Edmund Parabolic Reflectors

 Subject: Re: Edmund Parabolic Reflectors "Dave J" <> Wed, 04 Aug 2004 19:39:41 -0000
 ```--- Mike Feldman wrote: > Gregory Kunkel wrote: > > > The math of parabolas states that the width of > > a parabola at the level of the focal point is > > 4 times the focal point. So each of the parabolic > > dishes have a depth equal to its focal length. > > That's true given the assumption that the design > happens make the depth of the dish equal to focal > length, but there's nothing mathematical forcing > the manufacturer to this constraint. > y = kx^2 y'= 2kx y' = 1 = 2kx at focus x = 1/(2k) y = k(1/2k)^2 y = k/4 Is that right? It's been too long... > > So the 18" has a depth of 4.5" and the 24 inch > > has a depth of 6". > > That being said, the Edmund dishes are in fact as > deep as their focal length, and my 24" diameter > dish measures 6" deep. It seems to me that there > was some discussion here or on a related list > about the Telinga dishes being deeper than their > focal length, and that's important for sound > reflectors more so than for optical reflectors. > > -- Mike I do wonder if the edge of the dish would be a source of wind noise, and if the mic might be wind-shielded if lower, but I would think that gain might be optimized if the mic was higher -- but then I guess this would depend on the shape of the mic element and its pattern... ________________________________________________________________________ ________________________________________________________________________ ```
 Current Thread Re: Edmund Parabolic Reflectors, (continued) Re: Edmund Parabolic Reflectors, Gregory Kunkel Re: Edmund Parabolic Reflectors, Dave J Re: Edmund Parabolic Reflectors, Gregory Kunkel Re: Edmund Parabolic Reflectors, Walter Knapp Re: Edmund Parabolic Reflectors, Walter Knapp Re: Edmund Parabolic Reflectors, Mike Feldman Re: Edmund Parabolic Reflectors, Eric Benjamin Re: Edmund Parabolic Reflectors, Gregory Kunkel Re: Edmund Parabolic Reflectors, Mike Feldman Re: Edmund Parabolic Reflectors, Jim Morgan Re: Edmund Parabolic Reflectors, Dave J <= Re: Edmund Parabolic Reflectors, Gregory Kunkel Re: Edmund Parabolic Reflectors, Gregory Kunkel Re: Edmund Parabolic Reflectors, Rich Peet Re: Edmund Parabolic Reflectors, Mike Feldman Re: Edmund Parabolic Reflectors, Jim Morgan RE: Edmund Parabolic Reflectors, Martyn Stewart Re: Edmund Parabolic Reflectors, Dave J Re: Edmund Parabolic Reflectors, Klas Strandberg Re: Edmund Parabolic Reflectors, Klas Strandberg Re: Edmund Parabolic Reflectors, Jim Morgan