Only reason why the feed arm is longer on a higher gain dish or grid is because the grid or dish is larger and the focal point is further away from the dish so the arm has to be longer but that is independent of frequency because the focal point will always be at the same place on the same dish no matter frequency.
Think of a dish as a magnifying glass. Depending on the size and shape of the glass you have to hold it so far away to get best magnification. Remember when you where kid and toasted ants with a magnifying glass you had to hold it so far away from the ant to get that really strong white pinpoint on the ant. If you took a different size glass you had to change the distance but the distance was always the same for the one particular glass no matter what kind of light source (sun, light bulb, fluorescent, candle). The same is true with a dish / grid. The size and shape of it determine where all the "light" (in our case RF) is being strongest bunched up and the frequency is just different light sources. Replace the feed that is designed for a different frequency on the dish/grid and that grid now work on that frequency. But with a grid the higher frequency your wanting to use the closer the spacing between the grid members has to be to be the most efficient. 1" works good for 900 and 2.4 but 0.5" is recommended for 5Ghz or higher. On a solid dish you have no such issues or concerns since it's a "perfect" mirror. / Eje Dear animal protection activists. No ants where harmed in this telling... ;) -----Original Message----- From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On Behalf Of Josh Luthman Sent: Wednesday, October 21, 2009 9:56 AM To: WISPA General List Subject: Re: [WISPA] Identifying 2ft dish frequency 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! Join today! > > > http://signup.wispa.org/ > > > > > ------------------------------------------------------------------------ > > -------- > > > > > > WISPA Wireless List: wireless@wispa.org > > > > > > Subscribe/Unsubscribe: > > > http://lists.wispa.org/mailman/listinfo/wireless > > > > > > Archives: http://lists.wispa.org/pipermail/wireless/ > > > > > > > > > > > > > > > > > ------------------------------------------------------------------------ > > -------- > > WISPA Wants You! Join today! > > http://signup.wispa.org/ > > ------------------------------------------------------------------------ > > -------- > > > > WISPA Wireless List: wireless@wispa.org > > > > Subscribe/Unsubscribe: > > http://lists.wispa.org/mailman/listinfo/wireless > > > > Archives: http://lists.wispa.org/pipermail/wireless/ > > > > > > > > > > ---------------------------------------------------------------------------- > ---- > > WISPA Wants You! Join today! > > http://signup.wispa.org/ > > > > > > ---------------------------------------------------------------------------- > ---- > > > > WISPA Wireless List: wireless@wispa.org > > > > Subscribe/Unsubscribe: > > http://lists.wispa.org/mailman/listinfo/wireless > > > > Archives: http://lists.wispa.org/pipermail/wireless/ > > > > > > ---------------------------------------------------------------------------- > ---- > WISPA Wants You! Join today! > http://signup.wispa.org/ > > ---------------------------------------------------------------------------- > ---- > > WISPA Wireless List: wireless@wispa.org > > Subscribe/Unsubscribe: > http://lists.wispa.org/mailman/listinfo/wireless > > Archives: http://lists.wispa.org/pipermail/wireless/ > > > > > > ---------------------------------------------------------------------------- ---- > WISPA Wants You! Join today! > http://signup.wispa.org/ > > ---------------------------------------------------------------------------- ---- > > WISPA Wireless List: wireless@wispa.org > > Subscribe/Unsubscribe: > http://lists.wispa.org/mailman/listinfo/wireless > > Archives: http://lists.wispa.org/pipermail/wireless/ > ---------------------------------------------------------------------------- ---- WISPA Wants You! Join today! http://signup.wispa.org/ ---------------------------------------------------------------------------- ---- WISPA Wireless List: wireless@wispa.org Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/ -------------------------------------------------------------------------------- WISPA Wants You! Join today! http://signup.wispa.org/ -------------------------------------------------------------------------------- WISPA Wireless List: wireless@wispa.org Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
