Right on. Did you know you can find the focal point, even of an off-center feed, of a solid parabolic by busting a mirror? Yeah, break a mirror into a thousand pieces. Use a glue stick or rubber cement to glue 30 - 40 of the pieces to the dish surface. Using a car headlight or really bright flashlight BEAM, you can posit a die (singular dice) or a crumpled up piece of paper in the dish focus and "see" the focal point. Cool stuff.
It has nothing to do with frequency. A bright red light would work, so would a green one. Yep, even a gain microwave signal pointed at it would work; IF you could see microwaves. :-) It looks like Mark is rapidly answering his own question. Mike At 10:30 AM 10/21/2009, you wrote: >Feed length is based on dish size; where does the parabola focus. >Nothing to do with frequency, everything reflects the same. >Size of the feed horn isn't always an indicator either. Can depend on a >lot of things. > >Josh Luthman wrote: > > The feedhorn specifically. Maybe the length will help you > too. I know with > > higher gain the 5GHz grids are noticeably longer. > > > > Josh Luthman > > Office: 937-552-2340 > > Direct: 937-552-2343 > > 1100 Wayne St > > Suite 1337 > > Troy, OH 45373 > > > > "When you have eliminated the impossible, that which remains, however > > improbable, must be the truth." > > --- Sir Arthur Conan Doyle > > > > > > On Wed, Oct 21, 2009 at 10:48 AM, Brad Belton <b...@belwave.com> wrote: > > > > > >> Hmmm, pretty sure a 2' dish is a 2' dish regardless of frequency...or are > >> you speaking of the diameter of the feed? > >> > >> Best, > >> > >> > >> Brad > >> > >> -----Original Message----- > >> From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On > >> Behalf Of Josh Luthman > >> Sent: Wednesday, October 21, 2009 9:40 AM > >> To: WISPA General List > >> Subject: Re: [WISPA] Identifying 2ft dish frequency > >> > >> Can you measure diameter and compare it with the 2.4 and 5.8 GHz dishes? > >> Never thought about it but they would have to be different sizes. > >> > >> Josh Luthman > >> Office: 937-552-2340 > >> Direct: 937-552-2343 > >> 1100 Wayne St > >> Suite 1337 > >> Troy, OH 45373 > >> > >> "When you have eliminated the impossible, that which remains, however > >> improbable, must be the truth." > >> --- Sir Arthur Conan Doyle > >> > >> > >> On Wed, Oct 21, 2009 at 10:34 AM, Mark McElvy <mmce...@accubak.com> wrote: > >> > >> > >>> I happen to know they are either 5.8 or 2.4 as this was the only > >>> equipment I have found of theirs, they left it all when they went out of > >>> business. > >>> > >>> Mark McElvy > >>> AccuBak Data Systems, Inc. > >>> 573.729.9200 - Office > >>> 573.729.9203 - Fax > >>> 573.247.9980 - Mobile > >>> http://www.accubak.com/ > >>> http://www.accubak.net/ > >>> Nationwide Internet Access > >>> Accurate backups for your critical data! > >>> > >>> > >>> -----Original Message----- > >>> From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On > >>> Behalf Of ccrum > >>> Sent: Wednesday, October 21, 2009 9:29 AM > >>> To: WISPA General List > >>> Subject: Re: [WISPA] Identifying 2ft dish frequency > >>> > >>> Got a spectrum analyzer and a frequency generator? Or a good network > >>> analyzer will do, but most people don't have one laying around. The > >>> feeds could literally be anything. You might be better off just calling > >>> the MFG of the dish and buying new feeds in the range you want unless > >>> you you have a few hours of extra time on your hands. > >>> > >>> Cameron > >>> > >>> Mark McElvy wrote: > >>> > >>>> I have 4 two ft dishes that where pulled down when the previous wisp > >>>> went out of business. There are no markings on them and I need to > >>>> determine frequency and polarity. > >>>> > >>>> > >>>> > >>>> Mark McElvy > >>>> AccuBak Data Systems, Inc. > >>>> > >>>> > >>>> > >>>> > >>>> > >>>> > >>>> > >>>> > >>>> > >>> ------------------------------------------------------------------------ > >>> -------- > >>> > >>>> WISPA Wants You! 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