The best way to do this is to set up a cpe unit at your FURTHEST customer site and one at your CLOSEST site.
Aim for the best signal at the furthest site, then check at the closest site. If you need more signal at the closer site just aim down a little bit more and make sure that the signal is still OK at the far site. Me, I just eyeball them. Antennas are far from perfect. A couple of * off will normally make little or no difference in real world coverage. marlon ----- Original Message ----- From: "Cliff Olle" <w...@eccentrixtechnologies.com> To: "'WISPA General List'" <wireless@wispa.org> Sent: Monday, March 09, 2009 10:51 PM Subject: Re: [WISPA] 900 Downtilt at 300' > Interesting, I never would have thought that much. I was thinking more of > about 3-4 degrees. > > > -----Original Message----- > From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On > Behalf Of Tom DeReggi > Sent: Monday, March 09, 2009 11:43 PM > To: WISPA General List > Subject: Re: [WISPA] 900 Downtilt at 300' > > I disagree, Precise Tilt does matter quite a bit with Tiltek 900Mhz > sectors. > > Let me give an example of mounted at 400ft with Tiltek sectors having 17 > deg > > vert beamwidth. > > 8 deg downtilt, min .25 miles, max horizon. > > 9 degree downtilt, min .24 miles, max 8.6 miles. > > 10 degree downtilt, Min distance .22 miles, Max distance 2.8 miles. > > 11 deg downtilt, min .21 miles, Max 1.7 miles > > Near field coverage is rarely a problem with 900Mhz, regardless of the > tilt. > But what people forget is how much the far field is effected by just a > single degree. > > The difference between 9 versus10 degrees is the difference of "5 miles !" > coverage at optimal signal strength. > The difference between 8 versus 10 degrees is the difference of whether > you > interfere with your other towers 30 miles away versus 3 miles away. > > With 900Mhz, EVERY DB counts. The reason is two fold. 1) The noise floor > is > > ften high. 2) Its very easy to get colocated AP antenna self interference, > when foliage can degrade the signal of a single link severally. For > example, > > the Front-to-back isolation loss could be equivellent to the loss of > foliage > > in a path. > > The goal is to get the highest signal uniformally to the largest area > within > > your desired coverage area. Then you can always lower CPE transmit power > as > needed on links without foliage loss. In my 900 deployments, I have found > that 3db lost or gained can be the difference between a typically good > versus bad link. > > Now, its true the above beamwidths are only the distances that show "3 db" > loss, so a 10 degree downtilt, sector will still have a significant amount > of signal going out to and heard from the the horizon. But every DB > counts. > > The critical question becomes do you mount high or not? Higher avoids more > trees. HIgher hears more interference. We found what was best for us was > to > go higher, but add more downtilt. We shoot for 10 degree downtilt. But it > can be a delicate balance, dependent on your environment and noise levels > and locations. We will usally put a larger focus on reducing noise to our > adjacent cell sites, even if at the cost of gain to our intended coverage > area. > > Tom DeReggi > RapidDSL & Wireless, Inc > IntAirNet- Fixed Wireless Broadband > > > ----- Original Message ----- > From: "Cliff Olle" <w...@eccentrixtechnologies.com> > To: "'WISPA General List'" <wireless@wispa.org> > Sent: Monday, March 09, 2009 9:25 PM > Subject: [WISPA] 900 Downtilt at 300' > > >> For the 900 Mhz connectorized AP (by cyclone) with the 120 tiltek >> antenna, >> if I am mounted at 300', what amount of down tilt is normal? >> >> >> >> > ---------------------------------------------------------------------------- > ---- >> WISPA Wants You! 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