We just tore ours down, but our corn crib was 30 - 40 feet tall.
----- Mike Hammett Intelligent Computing Solutions http://www.ics-il.com -------------------------------------------------- From: "Josh Luthman" <[email protected]> Sent: Tuesday, February 23, 2010 9:11 AM To: "WISPA General List" <[email protected]> Subject: Re: [WISPA] That black magic > That profile suggests at 31 feet the customer should see the light > (the black LOS line). Was that where they looked for the light, or > lower? I would have to guess the corn crib was not nearly 31 feet. > > I think the whole US has 3m and 10m data - > http://www.cplus.org/rmw/dataen.html > > Josh Luthman > Office: 937-552-2340 > Direct: 937-552-2343 > 1100 Wayne St > Suite 1337 > Troy, OH 45373 > > “Success is not final, failure is not fatal: it is the courage to > continue that counts.” > --- Winston Churchill > > > > On Tue, Feb 23, 2010 at 10:05 AM, Mike <[email protected]> wrote: >> I have a bright beacon I can turn on at the top of this tower. On a >> clear >> night recently, I turned it on. Even a ways up a corn crib he could NOT >> see >> the light. I think the terrain data is accurate. The alphimax site, >> once >> you create the path lets you go into Google Earth and "see" the hill. >> This >> part of the world doesn't have high resolution imagery archived yet, but >> I >> CAN see the ridge when I follow along the path. >> >> -----Original Message----- >> From: [email protected] [mailto:[email protected]] On >> Behalf Of Josh Luthman >> Sent: Tuesday, February 23, 2010 9:01 AM >> To: WISPA General List >> Subject: Re: [WISPA] That black magic >> >> To begin with, are you sure there is a bump there? Could it be bad >> meter resolution? >> >> Josh Luthman >> Office: 937-552-2340 >> Direct: 937-552-2343 >> 1100 Wayne St >> Suite 1337 >> Troy, OH 45373 >> >> “Success is not final, failure is not fatal: it is the courage to >> continue that counts.” >> --- Winston Churchill >> >> >> >> On Tue, Feb 23, 2010 at 9:55 AM, Mike <[email protected]> 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 >>> >>> [email protected] >>> >>> >>> >>> >>> >>> >>> >>> >>> >> ---------------------------------------------------------------------------- >> ---- >>> WISPA Wants You! Join today! >>> http://signup.wispa.org/ >>> >> ---------------------------------------------------------------------------- >> ---- >>> >>> WISPA Wireless List: [email protected] >>> >>> Subscribe/Unsubscribe: >>> http://lists.wispa.org/mailman/listinfo/wireless >>> >>> Archives: http://lists.wispa.org/pipermail/wireless/ >>> >> >> >> ---------------------------------------------------------------------------- >> ---- >> WISPA Wants You! 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