"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