The ladder on the outside of the corn crib is probably a little less than 20 feet. I have seen the beacon close to 25 miles away. It is a bright amber rotating beacon. Yes at 31 foot, the LOS should be there, but more than half of the Fresnel zone will be impeded.
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Josh Luthman Sent: Tuesday, February 23, 2010 9:12 AM To: WISPA General List 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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