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! 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/
