I would assume that if John Deere, etc. are selling systems, they're FCC certified.
John Deere is coming out with a 450 MHz product for challenging RF situations, but the 900 MHz will still be the default product. ----- Mike Hammett Intelligent Computing Solutions http://www.ics-il.com -------------------------------------------------- From: "Justin Wilson" <j...@mtin.net> Sent: Wednesday, February 24, 2010 10:59 AM To: "WISPA General List" <wireless@wispa.org> Subject: [WISPA] 900MHZ Farm GOS..Was: That black magic > Are the 900 MHZ systems the farm operations are using FCC Certified? > Anyone > have some details on them? I have been on towers where such systems exist. > Interested in any info others have on them. > > Justin > > -- > Justin Wilson <j...@mtin.net> > CCNA CCNT Mikrotik Advanced > http://j2sw.mtin.net/blog > ³My posts are my opinions.² > > > > From: David Hulsebus <cont...@portative.net> > Reply-To: WISPA General List <wireless@wispa.org> > Date: Wed, 24 Feb 2010 11:50:08 -0500 > To: WISPA General List <wireless@wispa.org> > Subject: Re: [WISPA] That black magic > > We see some of the same interference issues. It was actually much better > when all the cordless phones were 900, verses meters, farm operations, > etc... > > Yes it's NLOS, if I went up another 40 ft I would have LOS. With NLOS > we only have about 25 yards of trees to deal with 100 yards or so from > the house, but no dirt. He's 1.35 miles from the tower, the AP is 150 > above his GL. We do use a Cushcraft 906 antenna on his end and an Antel > 120 deg, 3 deg electrical down tilt on the tower that puts out 34.8 > EIRP. A filter we changed out a couple of years ago dropped our output a > bit more than a db. Now that the beans are gone, his signal stabilized > and improved from a fluctuating -75 to -83 back to a -70 > > This is an older CCU3100 WaveRider system that doesn't run OFDM, but > DSSS. I tried a panel antenna instead of the yagi and it improved the > fluctuation some, but didn't improve the signal like going up 10 ft did. > So I think you are correct that the changes in multipath from a little > wind and lots of hardened leafs and beans reflected the signal more than > when they had enough moisture to absorb more than reflect. > > Dave > > Mike wrote: >> 900 MHz doesn't work well around here. The farmers have deployed GPS >> navigation systems using those frequencies. >> >> Was the bean path you had NLOS? I'm curious what effects it had. I have >> seen a four foot change in elevation work like black magic. I think the >> beans get to blowing in the breeze and because there are hundreds of >> thousands of little hard points that randomly diffract the signal it >> fades. >> I saw this on a knife edge diffraction path as well as a distant, path >> where >> the CPE had to be mounted low to clear large branches of an oak tree 20 >> feet >> overhead. The next field over was a bean field one year and caused fits >> for >> a couple weeks, I believe because of the low angle. Is it that OFDM can >> survive in a multipath environment until the individually randomized >> signals >> number in the thousands? >> >> Mike >> >> -----Original Message----- >> From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On >> Behalf Of David Hulsebus >> Sent: Tuesday, February 23, 2010 3:04 PM >> To: WISPA General List >> Subject: Re: [WISPA] That black magic >> >> Mike, Interesting you mentioned soy beans. I have a customer >> (900-WaveRider) who was installed for 5 yrs next to a corn field. The >> crop was replaced with soy beans this past year and a month before >> harvest, as the beans dried out, we started having signal fluctuation >> issues. We raised the antenna 10 ft and the problem went away. It was >> their first issue in 5 yrs. >> >> Dave >> >> >> >> Mike wrote: >> >>> I need to do a reality check with those of you familiar with knife edge >>> diffraction as a propagation medium. First, I should paint the scene: >>> >>> >>> >>> I have a corporate farmer almost 16 miles away who is motivated. His >>> options are satellite, dialup he currently uses, or us. >>> >>> >>> >>> A spectrum sweep of the property found absolutely no 2.4 signals. By in >>> large, these rural areas are very quiet. >>> >>> >>> >>> There are no trees or obstructions in the near field or out quite a >>> ways. >>> However, there is a ridge almost half way between us. I am embedding an >>> image of the path here created with alphimax.com path estimator. >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> I have a test unit which is a 19 dB panel/radio with an AP fastened to >>> the >>> back. It lets me hand hold a test unit and see what it sees on a >>> laptop. >>> Standing on the ground on his property we got an ALMOST usable signal in >>> a >>> short test. He has a 35 foot TV tower next to the house on which we >>> would >>> install. >>> >>> >>> >>> Perhaps one would look at the path profile and common sense would >>> dictate >>> >> it >> >>> won't work. However, I use knife edge diffraction successfully on a >>> >> handful >> >>> of installs. Besides, black magic sometimes trumps common sense. >>> >>> >>> >>> I have never used this technique where the ridge is close to mid point. >>> >> On >> >>> all others the ridge was closer to the user. All of them work except >>> when >>> tropospheric ducting enters into the equation, with one exception. I >>> have >>> told the users this is a 98% link and it WILL go down during those >>> events. >>> Earlier this winter we had a few days of ducting which caused a couple >>> of >>> them to fade. I saw a 15 dB fade on those. Statistically, ducting >>> should >>> only affect this area 20 some hours a year. >>> >>> >>> >>> The single exception was when the obstructing hill had soy beans growing >>> >> on >> >>> it. That particular one went down in late fall when the beans were >>> ready >>> for harvest. The previous 2 years the field had corn planted on it and >>> >> had >> >>> absolutely no issues. I think dry beans affect the signal because they >>> >> are >> >>> no longer "row" polarized and randomly scramble the signal beyond use. >>> >> Once >> >>> the beans were harvested, the signal came back like usual. >>> >>> >>> >>> On this path in question, I found the ridge. There are no trees, >>> instead >>> >> it >> >>> is farmed. There is corn stubble on it right now. >>> >>> >>> >>> I am curious what others have found in these NLOS situations. Because >>> the >>> obstruction is mid path, will the signal still be there next fall as it >>> is >>> now? Are mid path obstructions on a long path better than obstructions >>> closer to one end? Am I absolutely stupid for even considering this >>> install? >>> >>> >>> >>> I went over all the physics involved and told him of my experiences. >>> Like >>> >> I >> >>> said, he is motivated. I told him I wouldn't tie him into a contract, >>> but >>> we'd go month by month and if we found later in the year it wasn't >>> >> working, >> >>> we'd cut our losses. He was OK with that. >>> >>> >>> >>> Since I respect the viewpoints of many of you, bring it on! >>> >>> >>> >>> >>> >>> Friendly Regards, >>> >>> >>> >>> Mike >>> >>> >>> >>> Mike Gilchrist >>> >>> Disruptive Technologist >>> >>> Advanced Wireless Express >>> >>> P.O. Box 255 >>> >>> Toledo, IA 52342 >>> >>> Mike's >>> >>> >> <http://www.tamatoledonews.com/page/category.detail/nav/5001/Local-Columns.h >> >>> tml> Weekly Column >>> >>> 239.770.6203 >>> >>> m...@aweiowa.com >>> >>> >>> >>> >>> >>> >>> >>> ------------------------------------------------------------------------ >>> >>> >>> >>> >>> >> ---------------------------------------------------------------------------- >> ---- >> >>> 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! 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