Thats what I thought to, originally. Originally it was a Horiz omni at 175ft, vert omni at 150 feet. Then it became 3 sectors at 200ft. (I have 70-100ft mature trees around) But I had to move them up. I was able to double my customer coverage area by going to 425ft high. There becomes a ratio of how much loss your trees give compared to the interference of going higher. In my case thick pine trees, and dirt on rolling hills, caused much more loss than interference did. (And I was in very high Interference areas) Height was absolutely required, because it minimized the number of tree tops that the signal had to go through significantly. (Actually its feasible my antennas were at heights above the noise height, at 425 ft, considering many interfering rooftop 900Mhz antennas were on 5 story height buildings in nearby cities) But when being that high.... Adequate downtilt was absolutely required. I wanted to restrict to 3-5 mile coverage, for my core target. As was Horizontal pol, and High quality F/B ratio Tiltek sectors, as was 10-15 feet min verticle seperation per antenna.
Tom DeReggi RapidDSL & Wireless, Inc IntAirNet- Fixed Wireless Broadband ----- Original Message ----- From: "jp" <[email protected]> To: "WISPA General List" <[email protected]> Sent: Tuesday, March 10, 2009 9:39 AM Subject: Re: [WISPA] 900 Downtilt at 300' > The nicer the antenna, the more critical the aim is. A cheap 900 sector > will create a forgiving coverage pattern. A nice one like Tiltek or MTI > will have a well defined coverage pattern in the vertical direction. > > Personally, I wouldn't put 900 that high on a tower, as it would receive > too much interference in my areas. I'd be hesitant to put 900 over 150 > feet. But anything going that high up should be a high quality antenna, > anything else is false economy in the event it needs repair or > replacement. > > On Tue, Mar 10, 2009 at 12:42:57AM -0400, Tom DeReggi wrote: >> 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" <[email protected]> >> To: "'WISPA General List'" <[email protected]> >> 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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