Well, before he invests in an install, have him rent a lift truck or
something to see what he can see.

I have a few links that have this type of knife edge defraction. I run them
using 802.11 gear (Mtik/Tranzeo). When I allowed full on access to all the
speed I could provide, complaints came from these clients. When I throttled
them down to256/768/1M connections.. the complaints stopped and things were
more normalized to these clients.

ryan

On Tue, Feb 23, 2010 at 7:05 AM, Mike <m...@aweiowa.com> 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: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] 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 <m...@aweiowa.com> 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
> >
> >
> >
> >
> >
> >
> >
> >
> >
>
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