An 8or 9db antenna is about the best compromise to get both close in and the
longest possible range on a sailboat. You might go a little higher on a
trawler.

The cellular cards are great if you are primarily coastal but if you venture
down to the Caribbean the WIFI route is by far the most economical. When
you get into Cable & Wireless or Carricom territory the roaming fees can eat
you a new one even with an international roaming agreement with your
carrier.

--
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 Wed, 2 Apr 2008 13:16:17 -0700 (PDT), RichH
wrote:

I use the WaveRV marine antenna. Near metro, etc. areas I can get
adequate 'signal' 2-3 miles off the NE US coast. I have it mounted on
the stern rail ... seems to work better there.

You are height limited by the 15 ft USB cable are you not ?

There are obviously situations in a marina where height may be a
disadvantage but I've found that the higher the better if you are
trying to get above the nearby clutter and achieve some real distance.

My record is about 5 miles while actually underway, with the antenna
about 30 feet above the water. Last November I was solidly connected
for a month to an access point in Nags Head, NC while docked at a
marina 3 miles away on Roanoke Island.

"Glenn Ashmore" wrote in message
...
I think it would be wise to learn something about 2.4ghz wave propagation
and the Fresnel effect before you make that statement. If you just want a
couple of hundred yards range deck mounting is fine but for 2 miles plus
you need to be UP.

The maximum radius of the first Fresnel zone for 2 miles is 33 feet. So if
the tower is at 66 feet, the path is clear. Even if there was a large
reflection in the first zone, the maximum phase deviation would be 90
degrees, a phase quadrature signal, which would make the link even more
immune to fading and could increase the recieved signal strength as Wilbur
has reported.



By far the best solution is a waterproof wifi bridge at the masthead
connected by Ethernet with POE to a hub. Long range because there is
minimal coax loss and a wide Fresnel zone.

The Fresnel zone does not become any wider with that mounting installation,
it is just that there are less object to protrude into it.

The concept of a Fresnel zone is just a crude rule of thumb calculation to
prevent multipath. It doesn't take into account antenna beamwidth or any of
the physical properties of the in-path scatterers. It's great for
determining cell phone tower sites but is completely meaningless for
actually estimating what signals arrive at the antenna. You can place a
vertical aligned metal grid directly in the path of a horizontally polarized
signal and see virtually no effect yet the Fresnel rule of thumb would say
otherwise. The Fresnel rule of thumb sees no difference between vegetation
and buildings, it provides no insight into wave propagation at all.





--
Glenn Ashmore

In article s.com,
"Wilbur Hubbard" wrote:

"RichH" wrote in message
...
I use the WaveRV marine antenna. Near metro, etc. areas I can get
adequate 'signal' 2-3 miles off the NE US coast. I have it mounted on
the stern rail ... seems to work better there.


Thank you for telling it like it is. Experience under actual sailing
conditions trumps armchair bull**** every time.

Wilbur Hubbard

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" wrote in message
...
In article s.com,
"Wilbur Hubbard" wrote:

"RichH" wrote in message
...
I use the WaveRV marine antenna. Near metro, etc. areas I can get
adequate 'signal' 2-3 miles off the NE US coast. I have it mounted on
the stern rail ... seems to work better there.


Thank you for telling it like it is. Experience under actual sailing
conditions trumps armchair bull**** every time.

Wilbur Hubbard

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......

All you armchair 'experts' can run off at the mouth till the cows come home
but it proves nothing other than your heads are full of theoretical crap.
What matters is how things work on a sailboat in the real work-a-day world.

I sail. I've sailed most of my life and I know what works on a sailboat. I
have actual practical experience with wi-fi on a sailboat. I know of which I
speak. You theorists just spout lame ideas without ever having put them to
the test.


Wilbur Hubbard
(sending this e-mail via a pirate signal through the wi-fi matrix and 1/2
mile offshore with wi-fi omni antenna stuck out the main salon hatch a mere
four feet above the water. Signal strength 95%, Link Quality 97%)

"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.

On Wed, 2 Apr 2008 13:10:05 -0600, "Bob Crantz"
wrote:


"Wilbur Hubbard" wrote in message
tanews.com...
I have personal experience with respect to this topic. Putting a wi-fi
antenna at the masthead is the WRONG thing to do. You don't want it high
up. You want it low down. It gets better reception low. The signals seem
to be stronger low. Mount a good amplified antenna at deck level for the
best reception. No need to worry about long lengths of co-ax at all.

Here's a good antenna that works well and is priced reasonably.
http://www.radiolabs.com/products/wi...ne-antenna.php

Wilbur Hubbard


If your antenna is vertically polarized you could see a 3 dB increase in
signal if it placed over a conducting ground plane such as salt water.

6dB. Principle of superposition. No power splitting required for the
image. No change in antenna radiation impedance if the distance from
antenna to ground plane is large in terms of wavelengths,
as is likely to be the case in this situation.

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

"Goofball_star_dot_etal" wrote in message
news
On Wed, 2 Apr 2008 13:10:05 -0600, "Bob Crantz"
wrote:


"Wilbur Hubbard" wrote in message
ctanews.com...
I have personal experience with respect to this topic. Putting a wi-fi
antenna at the masthead is the WRONG thing to do. You don't want it high
up. You want it low down. It gets better reception low. The signals seem
to be stronger low. Mount a good amplified antenna at deck level for the
best reception. No need to worry about long lengths of co-ax at all.

Here's a good antenna that works well and is priced reasonably.
http://www.radiolabs.com/products/wi...ne-antenna.php

Wilbur Hubbard


If your antenna is vertically polarized you could see a 3 dB increase in
signal if it placed over a conducting ground plane such as salt water.

6dB. Principle of superposition. No power splitting required for the
image. No change in antenna radiation impedance if the distance from
antenna to ground plane is large in terms of wavelengths,
as is likely to be the case in this situation.



It's 3 dB in power and it's the Principle of Images that is used to remove
the ground plane and locate a virtual mirror image of the antenna. The
Principle of Superposition is used after the Principle of Images to
calculate the field. One would tend to say it's 6 dB in voltage but that is
misleading as the input impedance varies between the real and image and it
is power (actually energy) that is conserved. You're right about the spacing
being important.

Glory!

"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