On Thu, 3 Apr 2008 12:45:43 -0600, "Bob Crantz"
wrote:


"You" wrote in message
...


Willie, what you know about 2.4 Ghz RF Antenna Propagation and Path
Design, is smaller than you IQ, which you amply demonstrate every
time you post. Best you leave this to the folks, who actually have
Professional Experience, in the field......

You could start by using your Professional Experience and explaining what
Wilbur has done wrong and why what he observes cannot be happening. As to
any professed expertise on radio wave propagation all I've seen here are
antenna installers. I'm sure they are competent at installing antennas but I
really doubt they could make any accurate predictions of radio signal
propagation based upon what knowledge is required for installing antennas.
Thinking an antenna installer is expert on radio path propagation is like
thinking the person who drains the bedpan in the hospital is a doctor.

Even Wikipedia states:

http://en.wikipedia.org/wiki/Fresnel_zone

"If unobstructed, radio waves will travel in a straight line from the
transmitter to the receiver. But if there are obstacles near the path, the
radio waves reflecting off those objects may arrive out of phase with the
signals that travel directly and reduce the power of the received signal. On
the other hand, the reflection can enhance the power of the received signal
if the reflection and the direct signals arrive in phase. Sometimes this
results in the counterintuitive finding that reducing the height of an
antenna increases the S+N/N ratio.

Fresnel provided a means to calculate where the zones are where obstacles
will cause mostly in phase and mostly out of phase reflections between the
transmitter and the receiver. Obstacles in the first Fresnel will create
signals that will be 0 to 90 degrees out of phase, in the second zone they
will be 90 to 270 degrees out of phase, in third zone, they will be 270 to
450 degrees out of phase and so on. Odd numbered zones are constructive and
even numbered zones are destructive.[2]"



Please Note the following: "On the other hand, the reflection can enhance
the power of the received signal if the reflection and the direct signals
arrive in phase. Sometimes this results in the counterintuitive finding that
reducing the height of an antenna increases the S+N/N ratio"

Based upon your Professional Experience and all that you know about "2.4 Ghz
RF Antenna Propagation and Path Design" can you refute the above
statement? Did you get the part about "Odd numbered zones are constructive"?
That means they increase the received signal. By lowering his antenna he has
increased reflection in the first Fresnel Zone - "1" is an odd number the
last time I looked and his signal should increase.

If there is some new type of non-causal electromagnetics I'd love to hear
about it, so fill me in.

BTW "2.4 Ghz RF Antenna Propagation and Path Design" should be stated as
"2.4 GHz Radio Wave Propagation and Path Analysis". Antennas don't propagate
and paths are usually analyzed, not designed.

Wilbur's observations are supported by proven science.



That certainly soils Glen Ashmore's credibility. One would begin to
wonder if his success is built more on luck than knowledge. Here's
another website offering the same arguments:

http://www.zytrax.com/tech/wireless/fresnel.htm

It is really sad to see someone attempt to sully another's reputation
with misrepresentations and wind up ruining their own.

JT

"James Taggart" wrote
That certainly soils Glen Ashmore's credibility. One would begin to
wonder if his success is built more on luck than knowledge. Here's
another website offering the same arguments:

http://www.zytrax.com/tech/wireless/fresnel.htm



Did you actually READ that article? You probably stopped at the phrase
"With apologies to Mr. Fresnel" thinking it was a refutation when actually
the author was stating that he was vastly simplifying the principle.

The article confirmed exactly what I said! "The strongest signals are the
ones closest to the direct line between TX and RX and always lie in the 1st
Fresnel Zone. The rule of thumb is that 60% of the 1st Fresnel zone must be
clear of obstacles." With an omnidirectional 6 to 9db antenna (which is
the only practical option for a boat moving around an anchor or mooring) on
deck every hull and the water surface between you and the access point will
be within zone one. As you get higher the less water and other boats are
within zone one. The stronger you can get the signal in zone one the less
the reflections from the other zones matter. In other words, for best long
range performance Get Higher! D yourself a favor and learn something. Play
around with the range calculator they link to. It is similar to the one I
use.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Glenn Ashmore" wrote in message
...
"James Taggart" wrote
That certainly soils Glen Ashmore's credibility. One would begin to
wonder if his success is built more on luck than knowledge. Here's
another website offering the same arguments:

http://www.zytrax.com/tech/wireless/fresnel.htm



Did you actually READ that article? You probably stopped at the phrase
"With apologies to Mr. Fresnel" thinking it was a refutation when actually
the author was stating that he was vastly simplifying the principle.

The article confirmed exactly what I said! "The strongest signals are the
ones closest to the direct line between TX and RX and always lie in the
1st Fresnel Zone. The rule of thumb is that 60% of the 1st Fresnel zone
must be clear of obstacles."

If you read further it says 60% of the radius. I don't think the link could
tolerate obstructions on boresite that occupied less than 60% of the zone
(ie a skinny tower in the way)

With an omnidirectional 6 to 9db antenna (which is
the only practical option for a boat moving around an anchor or mooring)
on deck every hull and the water surface between you and the access point
will be within zone one.

Reflections from zone one are the strongest and additive - they increase the
signal strength. This could very well explain what Wilbur has been
experiencing.

As you get higher the less water and other boats are within zone one. The
stronger you can get the signal in zone one the less the reflections from
the other zones matter.

Wouldn't keeping the antenna low on the water eliminate any chance of
getting anything in zones other than zone 1 and maximize the signal in zone
1? How can you get the signal "stronger" in zone 1? Aren't the antenna
patterns and transmit power fixed? Keeping the antenna low keeps the power
in Zone 1.


In other words, for best long
range performance Get Higher!

For best long range performance get the longest unobstructed path and keep
obstructions out of the even zone numbers. This does not necessarily
maximize signal strength since there would be no additive reflections.

D yourself a favor and learn something. Play around with the range
calculator they link to. It is similar to the one I use.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

On Thu, 03 Apr 2008 18:44:20 -0400, James Taggart
wrote:

That certainly soils Glen Ashmore's credibility. One would begin to
wonder if his success is built more on luck than knowledge. Here's
another website offering the same arguments:

http://www.zytrax.com/tech/wireless/fresnel.htm

It is really sad to see someone attempt to sully another's reputation
with misrepresentations and wind up ruining their own.

The Fresnel effects are applicable in some circumstances, but in the
real world, gaining an unobstructed path via antenna height almost
always trumps everything else.

"Wayne.B" wrote in message
news

The Fresnel effects are applicable in some circumstances, but in the
real world, gaining an unobstructed path via antenna height almost
always trumps everything else.


Somebody already said this. The point of the discussion at hand is whether
Wilbur sees an increase in signal by mounting his wifi closer to the water.
Glen implied this was not so and cited the Fresnel effect and said further
that he is an expert installer with 60 systems to date. Upon checking facts
that can be checked we find, in fact, that Wilbur's signal can be increased
by mounting the antenna closer to the water - this was stated under
descriptions of the Fresnel effect (multiple references), contrary to Glen's
implications. Glen has not demonstrated professional courtesy and stepped
forward to admit that this is indeed so a condition of the Fresenel effect
and can happen and probably is what Wilbur is observing. It seems people are
more concerned with attempting to cast Wilbur in a poor light at the expense
of truth.

This contrasts sharply with Roger. If he makes a mistake or hears of
something new, he checks it out. His primary concern is the joy of learning,
he has no inflated ego to keep pumped up. Roger may have made many mistakes,
but he has done things correctly by a much greater factor. The love of what
he does comes before all things, that is why he can harbor no ill towards
others and he judges a book by its content, not its cover. He can be honest
about a mistake of his because he views mistakes as part of the learning
process, not an attack on his self esteem. A person who won't admit mistake,
attempts to sidestep it or cites irrelevant experience to somehow make
claims in science books false is a person who has never made many mistakes
and as a consequence has done very little right.

Looking at individuals in a newsgroup: the ones with a healthy perspective
can laugh with/at an idiot, ignore garbage and keep good things going; the
ones with a lesser perspective are the ones whining (over nothing), the ones
yelling "plonk", the ones yelling "ignore them" etc. For those who served in
the military think of the types in your unit that caused the most grief and
trouble for everyone else. It certainly wasn't those who were well adjusted
was it?

"James Taggart" wrote in message
...

That certainly soils Glen Ashmore's credibility. One would begin to
wonder if his success is built more on luck than knowledge. Here's
another website offering the same arguments:

http://www.zytrax.com/tech/wireless/fresnel.htm

It is really sad to see someone attempt to sully another's reputation
with misrepresentations and wind up ruining their own.

JT

Hey Jerk,

Glen probably does a bang up job on putting in Wi-Fi. He uses his knowledge
of the Fresnel effect to maximize performance. From installing tower systems
how would he know about little known effects down near the earth? If
anything, Glenn has a great reputation, his track record proves it.

BC