marine antenna choices?

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Are there other 2.4ghz antennae suitable for use marine use besides the 8db
unit from hyperlink?

I'd like to find one with a better vertical beam angle.  Having only 15
degrees and then dealing with the rocking motion would end up making the
target area pretty small.

It'd have to be capable of being mounted in a ratcheting mount, to allow
getting under low bridges.   The arch is about 9' above the waterline.

Thanks,
-Bill Kearney


Re: marine antenna choices?



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If you want something with a wider vertical pattern why not just get a
5dbi rubber duckie?  I doubt that such a small antenna will need to be
folded down for any bridge you'd really want to go under. ;-)

Mini-Box sells some $10 5.5dBi antennas that terminate in N-Male
connectors.  The intension is that you screw them directly onto the
N-female on the outside of their weatherproof cast aluminum box.  It
also looks like a nice way to mount an acess point outside.  I'm
sorely tempted to pick up one of their boxes and antennas.

       http://www.mini-box.com/s.nl/sc.8/category.19/.f

-wolfgang
--
Wolfgang S. Rupprecht                http://www.wsrcc.com/wolfgang /

Re: marine antenna choices?


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Yes, but I'm still faced with the challenge of getting it mounted.

I've got enough room inside the radar arch to put the router up there so my
RF cable lengths could remain quite short.

I'd consider using an N-female bulkhead socket if I could find an 8db (or
greater) antenna that would plug into it.  That way I could have the short
5db unit plugged in 'most of the time' and only use an 8db stick when
needed.  But I can't seem to find an 8db antenna with an N-male connector,
they all seem to have either a pigtail or an N-female on them.

Actually a plain bulkhead mount won't work as it can't adjust it's angle.
So I'd have to get some sort of adapter that'd let me use the antenna on a
regular ratcheting marine mount.

Although a bit of digging turns up some from Pacific Wireless.  Anyone tried
them?

http://www.pacwireless.com /

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I'd prefer something that looked good.  This is a brand new 37' boat, I'm
not about to go bodging up some hack on it.  I've got some dandy homemade
(metal mesh) parabolic screens setup on the home WiFi router and the wife
will have NONE of that on the new boat.

-Bill Kearney


Re: marine antenna choices?


Coming a bit late to this particular party (see ancient thread on
actual wireless [vs wired] wifi communications), I have a related
question:

Wolfgang S. Rupprecht wrote:
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How is it that a duck has such a wider pattern for an apparent
identical gain over a stick?

Looking at Hyperlink, my current antenna supplier for the stillborn
wifi communication project, the 8.5dBi stick I have is a very narrow
pattern compared to a similar duck.

Needless to say, and as discussed in this thread, wider is better.  I
already know that I have only enough knowledge to be dangerous but my
understanding (such as it is) has it that dBi is a measure of gain in
reception.  Thus, one 8.5dBi gain is the same as the other.

If that's so, why would anyone want a heavier, more expensive, taller
(of some issue on some boats) stick antenna over a duck?

Thanks.

L8R

Skip

Morgan 461 #2
SV Flying Pig   KI4MPC
http://tinyurl.com/p7rb4 - NOTE:new URL! The vessel as Tehamana, as we
bought her

"Believe me, my young friend, there is *nothing*-absolutely
nothing-half so
much worth doing as simply messing, messing-about-in-boats; messing
about in
boats-or *with* boats.
In or out of 'em, it doesn't matter.  Nothing seems really to matter,
that's
the charm of it.
Whether you get away, or whether you don't; whether you arrive at your
destination or whether you reach somewhere else, or whether you never
get
anywhere at all, you're always busy, and you never do anything in
particular; and when you've done it there's always something else to
do, and
you can do it if you like, but you'd much better not."


Re: marine antenna choices?


On 22 Jun 2006 11:31:37 -0700, "Skip - Working on the boat"

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The higher the gain the narrower the pattern, and vice versa.  That's
how the gain is achieved.

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The duck has lower gain -- a standard rubber duck is about 2 dBi.

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The gain won't be the same for different patterns.

--
Best regards,   FAQ for Wireless Internet: <http://Wireless.wikia.com
John Navas      FAQ for Wi-Fi:  <http://wireless.wikia.com/wiki/Wi-Fi
           Wi-Fi How To: <http://wireless.wikia.com/wiki/Wi-Fi_How_To
Fixes to Wi-Fi Problems:  <http://wireless.wikia.com/wiki/Wi-Fi_Fixes

Re: marine antenna choices?



John Navas wrote:

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Hmmm...

http://www.hyperlinktech.com/web/24ghz_802.11_rubber_duck_antenna_9dbi_rsp.php
and the one I have:
http://www.hyperlinktech.com/web/hg2409u.php

Both 8.5dBi antennae.

Well, technically, the duck is 9, and despite the "9" in the PN, the
stick is 8.5, but who's counting?

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Well, I certainly found that to be true in the inverse - the higher I
got in the sticks, the skinnier the pattern.

What's confusing to me is that the same dBi duck is so much fatter than
the stick...

L8R


Re: marine antenna choices?


On 22 Jun 2006 14:03:00 -0700, "Skip - Working on the boat"

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That isn't a standard "rubber duck" antenna.

--
Best regards,   FAQ for Wireless Internet: <http://Wireless.wikia.com
John Navas      FAQ for Wi-Fi:  <http://wireless.wikia.com/wiki/Wi-Fi
           Wi-Fi How To: <http://wireless.wikia.com/wiki/Wi-Fi_How_To
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Re: marine antenna choices?



John Navas wrote:

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Well, let me rephrase that then.

Who would want a stick when a "non-standard" rubber duck (or whatever
other label Hyperlink or any other manufacturer may choose to apply)
has a much fatter pattern, lighter weight and considerably lesser cost?

L8R

Skip

Morgan 461 #2
SV Flying Pig   KI4MPC
http://tinyurl.com/p7rb4 - NOTE:new URL! The vessel as Tehamana, as we
bought her

"Twenty years from now you will be more disappointed by the things you
didn't do than by the ones you did do. So throw off the bowlines. Sail
away from the safe harbor. Catch the trade winds in your sails.
Explore.
Dream. Discover."   - Mark Twain


Re: marine antenna choices?



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Something doesn't look right with those two radiation patterns.  Both
antennas are purely passive (eg. no amplifiers) so the only way they
can shape the radiation pattern is to add the radiation patterns of
the sub sections together to change the overall shape.  Cutting a foot
off of the side of the blanket and sewing it on the top won't change
the overall size of the blanket.  Same with the radiation pattern.
The extra gain that gets added to the major lobe has to come from
somewhere else.  My gut reaction is that the duckie pattern got mixed
up and thats really a 5.5dbi radiation pattern that got mislabelled.
Jeff?

-wolfgang
--
Wolfgang S. Rupprecht                http://www.wsrcc.com/wolfgang /

Re: marine antenna choices?


"Wolfgang S. Rupprecht"
wroth:

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http://www.hyperlinktech.com/web/24ghz_802.11_rubber_duck_antenna_9dbi_rsp.php

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Yep.  They're "stylized", also known as faked.  Perhaps generated from
a computer model in free space and without the influence of the
connected wireless router.  In addition, the proximity of the 2nd
antenna in a diversity derrangment is a big problem with high gain
antennas.  There's minimal interaction between antennas when the gain
is fairly low (i.e. 2dBi), but it really gets weird looking when the
gain increases.   In other words, the plots are not real (or even
close to real world).

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Nope.  It's a hand drawn model of what one antenna would look like in
free space and without any connections to equipment or reality.  I do
those all the time to "beautify" the antenna patterns.  When I throw
in the effects of equipment, other antennas, cables, mounting, and
even the table, the computer generated pattern gets really weird.

The Hyperlinktech patterns are weird in another way.  Look carefully
at the scale.  The outer ring is 0dB. Then there's -3dB, -10dB, -20dB,
and so on.  However, a proper antenna pattern should have the log
scale marked with equal distances between equal number of decibels.
These graphs are double logarithmic for some stupid reason, which
makes the beamwidth look very wide.  Plotted on a real log scale, the
-3dB beamwidth would be pencil thin or about 12 degrees for a 9dBi
antenna.  However, they didn't even bother faking that part correctly.
The plot shows a beamwidth of 30 degrees, which is correct for a 5dBi
omni.  However, the 5.5dBi omni has an even weirder plot:
  http://www.hyperlinktech.com/web/hg2405rd_rsp.php
which proclaims a beamwidth of 120 degrees, which is pure baloney.  

I would say the plots are total hand drawn fabrications performed by
someone with no clue as to what they should look like for the alleged
antenna gains.

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Why me?

--
Jeff Liebermann     jeffl@comix.santa-cruz.ca.us
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Re: marine antenna choices?


On Wed, 21 Jun 2006 13:58:21 -0400, "Bill Kearney"

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See the Marine section of the Wi-Fi Wiki below.

--
Best regards,   FAQ for Wireless Internet: <http://Wireless.wikia.com
John Navas      FAQ for Wi-Fi:  <http://wireless.wikia.com/wiki/Wi-Fi
           Wi-Fi How To: <http://wireless.wikia.com/wiki/Wi-Fi_How_To
Fixes to Wi-Fi Problems:  <http://wireless.wikia.com/wiki/Wi-Fi_Fixes

Re: marine antenna choices?


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Which, informative as it may be otherwise, contains nothing of use in
answering my questions.


Re: marine antenna choices?


On Wed, 21 Jun 2006 22:12:04 -0400, "Bill Kearney"

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I disagree.

--
Best regards,   FAQ for Wireless Internet: <http://Wireless.wikia.com
John Navas      FAQ for Wi-Fi:  <http://wireless.wikia.com/wiki/Wi-Fi
           Wi-Fi How To: <http://wireless.wikia.com/wiki/Wi-Fi_How_To
Fixes to Wi-Fi Problems:  <http://wireless.wikia.com/wiki/Wi-Fi_Fixes

Re: marine antenna choices?


On Wed, 21 Jun 2006 13:58:21 -0400, "Bill Kearney"

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Disclaimer: I've never done a marine wi-fi installation so much of the
following is speculation and guesswork.  I did work for Intech
designing marine VHF, SSB, ADF radios, so I know a bit about vessel
installations.

Ever consider making a gimbal mount that maintains a vertical
orientation?  Kinda like the gimbal rail mounts for keeping drinks
from sloshing.  The truly sloppy way would be to just hang the 8dBi
omni antenna upside down from the flexible coax cable and let gravity
keep it vertical.  A weight might be required at the antenna tip.
However, I suspect you might find this aesthetically disgusting and
want something a bit more elegant.

If you can find something with a ball and socket arrangement, the
antenna base can be screwed into the top of the ball, and a
counterweight screwed into the bottom of the ball.  As the vessel
rolls with the waves, the antenna remains roughly vertical.

Instead of an omni antenna, I suggest something directional.  For
example, the common build it thyself biquad antenna has a vertical and
horizontal beamwidth of about 60 degrees with about 9-10dBi gain.
  http://802.11junk.com/jeffl/antennas/Biquad/index.html
You have to point the antenna at the access point, but then you can
swing and sway 30 degrees in any direction and it should still work.

One of my biquads was crammed into a 6" electrical box, which should
be sufficiently waterproof for marine use.  I'm a fan of pressurized
boxes but I didn't do it for this package.  Basic biquad construction:
  http://homepages.ihug.co.nz/~redwood4 /
  http://martybugs.net/wireless/biquad/index.cgi
You might need to do some silver plating of the copper.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558            jeffl@comix.santa-cruz.ca.us
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com               AE6KS

Re: marine antenna choices?


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I don't need connectivity THAT bad <grin>.  If it's rocking that much,
beyond what a 5db antenna might readily handle with a 15 to 30 degree
vertical beam, then I'm not likely to be getting much work done anyway.

But it does mean that using a flush bulkhead mount N-female will not be a
good idea.  I wouldn't be able to change the angle enough to fine tune it's
alignment.

I'd like to find a way to use a ratcheting mount and also have the ability
to swap antennae.  Most of what I'm seeing out there expects to use a
pigtail running through the socket or a pole mount.  I've not yet found a
pole mount suitable.  I'm open to suggestions on sources for one.  The
problems being finding something that's going to be resistant enough to the
harshness of a marine setup (full sun exposure all day, salt water, etc).
Beyond just being resistant to the elements it's preferable to have
materials that won't cause discoloration of the surfaces under them should
they corrode or otherwise lose their finish.  It's a white gelcoat on the
arch, stuff dripping makes things look ugly.  Up on the roof of a building
you might not care, on a white boat you do.

That way I could open up the possible antenna choices to those using an
N-female on the bottom and run a small N-male to RP-TNC pigtail on the WiFI
device inside the arch (or nearby).

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Yeah, I'd really like to keep it a clean-looking setup.  For both aesthetic
and resale value reasons.

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For in-marina use, or when docked at a fixed pier that'd be workable.  For
our home port, where I know the location fo the base station, it'd be great.
But when we're travelling I won't know where the base station is located and
I'm not sure I'd want to get into hunting for it.  I'd rather just switch to
a higher gain omni and let it do the work.  But then we're back to the
vertical beam issues.  The further we are from the base, the wider the
vertical spread so (hopefully) it'd work.

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Impressive stuff, thanks for the links!

I'm now looking to find a suitable way to mount an N-female equipped antenna
onto a powerboat radar arch.  Anyone know of suitable mounts?  Or a way to
'cleanly' attach a pole antenna to a marine-style ratcheting base?  The
ratcheting base is important not just for low-clearance situations but also
for changing the tilt.

-Bill Kearney


Re: marine antenna choices?



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Connectivity is currently the holy grail.  The search for connectivity
has some similar characteristics.

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Well, that means you can use a higher gain antenna.  However, I was
more concerned about the pointing accuracy than the rocking motion. If
the marina access point is sufficiently close, almost any antenna will
work.

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True.  However, a short piece of LMR-400 coax between the antenna and
the N feedthrough bulkhead connector might be sufficiently flexible to
orient the antenna.  What I'm concerned with is the omni radiationg
power in all manner of direction except the direction you want. That's
why I suggested a directional antenna.

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The typical marine antenna mount has a nifty lever for lowering the
antenna.  However, adjusting it for vertical requires a wrench.  There
is no fine adjustment as the meshing "teeth" are rather coase.

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Add UV embrittlement and not having accumulated salt jam the
mechanism.  I could probably design a custom mount for the intended
purpose out of stainless.  Unfortunately, I don't know of any existing
commerical product that will tilt, swivel, rotate, aim, and remain
vertical.  I was thinking of modifying a motorized outdoor video
camera mounting and adding circuitry that would maintain a fixed
direction once set as stabilized by a solid state gyro.  Something
like this camera:
|  http://www.elmousa.com/cctv/pdfs/PTC_401CIP_Flyer.pdf
|
http://www.2mcctv.com/product_info-SecurityCameras-PanTiltZoom-CopUSACPTZ1.html
|
http://www.2mcctv.com/product_info-SecurityCameras-PanTiltZoom-CopUSAASH65NV.html
but without the camera.

Then, there's the manual version.  See:
|  http://www.ram-mount.com/camera_mount/camera_mounts.htm
Camera mounts.  Some have knobs for easy adjustment.  Install a
(white) plastic box with a biquad antenna inside on one of these.
Point it in the general direction of the access point.  It's not
motorized or fancy, but it sure it cheap and easy.

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It's worth the effort aiming the antenna.  A few marina maps I've seen
show the exact location of the access points.  You can probably get
the location by just asking.

Hunting is not that horrible.  Most client radios have a signal
strength indication.  They're not particularly responsive, so it won't
exactly be easy to adjust.  If you were to use a 24dBi barbeque grill
dish antenna, with a 7 degree beamwidth, aiming will be almost
impossible.  However, a 60 degree wide 9dBi biquad is very easy to
aim.

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The omni vertical beamwidth issue is a killer.  It's so bad that it
even happens on vehicles.  One mobile wi-fi user tells me that he had
to install a bubble level from a 4wd shop to make sure the antenna is
fairly level.  Worse, some access points are overhead on light poles
and rooftops, which are impossible to "aim" the vehicle (short of
using a bumper jack).

Omni's also have a bigger problem.  They pickup garbage from other
wi-fi users from all directions.  In a marina, you're probably also
going to have reflection problems from masts and rigging.  A
directional antenna will not eliminate these problems, but certainly
will reduce them dramatically.

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N to N bulkhead feedthough connector with a pair of drilled metal
plates (washers) on both sides for strengh.
|  
http://www.hyperlinktech.com/web/connectors/connector_information.php?SKU=AXA-NFNFB2
The antenna screws into one side of the feedthrough.  The coax cable
going to the radio into the other side.

--
Jeff Liebermann     jeffl@comix.santa-cruz.ca.us
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Re: marine antenna choices?


On Thu, 22 Jun 2006 10:23:55 -0700, Jeff Liebermann

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I suggest a high-grade tripod head.

--
Best regards,   FAQ for Wireless Internet: <http://Wireless.wikia.com
John Navas      FAQ for Wi-Fi:  <http://wireless.wikia.com/wiki/Wi-Fi
           Wi-Fi How To: <http://wireless.wikia.com/wiki/Wi-Fi_How_To
Fixes to Wi-Fi Problems:  <http://wireless.wikia.com/wiki/Wi-Fi_Fixes

Re: marine antenna choices?


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Hmmm, what're your thoughts on the panel type antenna for the base?  Which
ones, at what db, are worth considering?

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True, but there are several problems with directional antennae in this
situation.  The obvious one being the effort to get them aimed.  But there's
also the hassle of dealing with getting a mount that's adjustable 'enough'
that'll also withstand being up on a radar arch in a boat that goes over
35mph.  Using a NEMA box or other enclosure is problematic given the amount
of drag it'd incur.  That and there's a finite amount of room up on the arch
anyway.  I can fit another stalk up there, but not much more without it
looking crappy.

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Indeed, good point.

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I wouldn't need 'total' adjustability, being able to rotate about 180
degrees and tilt in 5-10 degree increments would probably be sufficient for
most situations.  Mainly, swing the antenna around and  tilt to better aim
'toward shore' when anchored in unfamiliar areas.

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Hah, it'd certainly be no small challenge getting the admiral to buy off on
THAT idea.  Glomex makes one that's only single axis but if you mounted it
on it's side you could probably rig up a way to use it to at least get
rotation.  Couple it with some sort of servo control on the PC and it'd be
able to hunt on it's own, heh.

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Those do not usually have enough clamping strength to handle being up on a
radar arch.  I've used the RAM mounts before, and they're great, but they
don't seem like the sort of that that'd work in this particular situation.

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So whose sells such a beast, designed for marine use?  No, I'm not making
one myself.

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Yes, this is true.  I actual fired up a drawing program and made some
diagrams plotting the beam widths over the expected distances.  The typical
15 degree beam width only allows a 20' aiming window at the distance I'd be
using at our home port.  Thus this whole tangent on considering swappable
antennae.  A pair of them; say a 5 and an 8db would probably cover most
situations.  I'd leave the 5db unit on their most of the time and only swap
out if I encountered really poor coverage.  The trick is in finding a way to
get one of them mounted that's reasonably easy to adjust.  I'm not finding a
lot of options on how to get an antenna that's expected to be on a
pipe-mount attached to a ratcheting marine mount.  I'd want to be careful
about starting to add extensions to the typical base as that also increases
the likely stresses on it.

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Another good point.  If I can find a way to rig up a solution that allows
easy swapping then at least I can switch to a directional when it becomes an
obvious problem.

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antenna
http://www.hyperlinktech.com/web/connectors/connector_information.php?SKU=AXA-NFNFB2
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Yeah, but that has zero adjustability.

I'm looking for ideas on getting an adjustable mount that'll handle the
typical N-type stick antennae.  I suppose a plate of some sort, or a
z-shaped angle bracket would work.  Spin a nut on the marine 1" thread mount
to hold it down and then put the antenna through the other side of the
bracket.  Any ideas on a source of something like this?  I'd want one
designed to survive a marine environment (as in, not rust out, drip and
discolor the gelcoat).

-Bill Kearney


Re: marine antenna choices?



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Panel/patch antennas are probably a good choice.  Most are easily
sealed and inherently waterproof.  They're also fairly cheap.
  http://www.fab-corp.com/home.php?cat=255
The big question is how big and how much gain.  Too much gain will
make the antenna excessively sensitive to vessel rocking and swinging.
Not enough gain will result in insufficient signal strength if the
signal is too low.  My guess(tm) is to size the antenna by the
appropriate -3dB beam width and take whatever gain results.   From a
random assortment of panel antennas from the above URL.
  Gain   -3dB beamwidth
  dBi     degrees
   8       60
  10       60
  12       40
  18       18
I would think 8 to 10dBi gain would be about right.  If the antenna is
easily removable, it might be useful to have two, low and high gain.

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Sigh.  There's also the blockage that might be presented by the radar
radome and other antennas up there.  It appears that an adjustable
fixed mount isn't going to work.  That leaves the motorized camera
mounts that I suggests might be more useful.  When underway, the panel
antenna can be pointed downward or edgewise to minimize wind
resistance.  White epoxy paint should help with the aesthetics
problem.  However, this is an engineering project, not a simple
installation.  Some method of control will need to be arranged.  I
suspect that the usual computer controlled gimbal mount won't work.

Speaking of engineering projects, I'm thinking of something like a
miniature version of the TV studio van with the telescoping dish
antenna mounted on the roof.  Probably too big and ugly, but
interesting.

It also seems you don't have much room on the arch.  That's going to
be a problem even with the original 8dBi omni antenna.  The problem
with end fed colinear antennas is that the bulk of the RF comes out
from the bottom of the antenna.  Of the bottom part of the antenna is
blocked by other antennas or structure, it's not going to work too
well.  That means a mast, which was your original idea, putting us
back where we started.

Perhaps a conglomeration of the adjustable gimbal mount, in place of
the usual tilt over VHF antenna mount, with a small fiberglass mast,
and an 8dBi omni antenna on top.  It still has to be adjusted
manually, but it will clear the other antennas, tilt over for bridges,
and can be aligned roughly vertically.

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Do you have the room to swing the antenna?  My guess is that the panel
will be about 10" across and mounted 2" from the center of rotation.
That means you need an 11" diameter clear area on the arch.

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It's easier to obtain forgiveness than permission.  I think what
you're looking for is simplicity.  How about a stainless "gooseneck"
contraption with a panel antenna on the end?  It would look kinda
funny, but is very easy to adjust (and move out to the way).

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I suggest a mechanical joystick or something simple.  Maybe a TV
remote control running a few relays that drive the motors.

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There are larger versions of such gimbal mounts.  John's suggestion of
using a camera tripod head is one variation.  I have a few similar
mounts (forgot the manufacturer) installed as panel antenna wall
mounts on mountaintops that get fairly high wind loads.  I have had
problems, but not from lack of rigidity.

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I don't know anyone that sells a commercial biquad.  However, a
panel/patch antenna is a good equivalent.
    http://www.fab-corp.com/home.php?cat=255
  
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One possibility that might work (no guarantees) is to use a client
radio with diversity.  Something like a WAP54G or WRT54G with DD-WRT
firmware.  Two omni antennas, on opposite ends of the arch, tilted
about 8 degrees outward from vertical.  That will give double the roll
angle.  Again, I'm not sure this will work.  If the client radio cant
switch antennas every time the vessel rolls, it won't play.  I guess I
can test it on the workbench, but don't have the time.

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Well, we're back to the stainless Shakespear 4187 tilt over mount.
Hire a machine shop to make a suitable pipe and adapter for the
antenna.  I've used while ABS plastic pipe to make masts and adapters,
but I think that will fail inspection by the high command.

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I'm beginning to think that mounting an antenna permanently is a bad
idea.  Perhaps a small tripod, suction cup, or rail mount with a panel
antenna and radio attached.  CAT5 cable to the computah.  Leave it
stowed when underway.  Deploy when anchored.

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The N-feedthru can be used as a mounting base.  A piece of LMR-400 is
stiff enough to support a small (6dBi omni antenna).  Wrap a spring
around the coax cable for additional stiffness.  It will act like a
gooseneck and take a set in any position.  However, it will look
terrible, probably not survive much wind, is not very water proof, and
probably too crude.

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Not that I know about.  There are adapters between the 1" - 14 thread
but not for an N connector.  However, somthing can be fabricated by a
machine shop.  The big problem is that the omni antenna has the coax
cable along the center line, while the Shakespear mount has a solid
center core.  The coax will need to exit somewhere.  The typical VHF
antenna uses 0.25" RG-58c/u which is flexible and easy to work around
the mount.  However, 2.4GHz wants LMR-400 which is about 0.4" in
diameter, is fairly stiff, and is not easy to work around the base.
The fairly large bend radius of the LMR-400 isn't going to help much.
This is not going to be easy.  

Need a starting drawing or sketch?  (Say no.  I'm overloaded).


--
Jeff Liebermann     jeffl@comix.santa-cruz.ca.us
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Re: marine antenna choices?


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Oh that's just great.  Yes, it's back to the notion of putting it up on some
sort of extension.

One thing you may not be taking into account is vibration.  This is a
powerboat, not a trawler or a sailboat.  Granted it's only a 37' express
cruiser, not an offshore racing catamaran.  If something's not *seriously*
well attached and tight it'll work loose in pretty short order.  Thus my
on-going resistance to a panel or shape other than a simple cylinder/mast.
The combination of windage and higher center of gravity makes using panels
or something in boxes a less-than-good idea.

I suspect we're zeroing in on using a standard mount, at least to start
with, that has an extension on top of it.  To which I'd use the usual pole
mount held with U bolts.  I'd just want to find ones made of a material
that's not going to corrode and make a mess.   I'll have to measure just how
much higher than the radome it would have to be.

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If the mast idea doesn't work it'd be worth considering.  I'm really looking
to avoid having to ever adjust this thing.  But in the few situations that
might warrant it the ability to do so would be nice.

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Marine-grade?  From what supplier?

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As I mentioned before, it's not soley about wind.  Wind load put on it at
35mph is one thing, couple that with pounding through waves and it's a lot
of stress.

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As opposed to the offerings from hyperlinktech?

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Yep, already planning on dd-wrt on a wrt54g.

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Hmmm, this might also help deal with obstruction by the radome.

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Again, an interesting idea.   I may just experiment a bit using a couple of
9db rubber ducks I've already got on a WRT54G here at home.  Besides
netstumbler what's a good signal strength charting program?

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Glomex and others sell both fiberglas and stainless extensions in a variety
of lengths.  I'd probably go with fiberglas to avoid having the weight make
the center of gravity higher.

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Eh, there's enough crap to stow and deploy all the danged time.  I'm looking
to actually have a laptop in the boat permantently.  As a gateway of sorts
of web, mail, proxying and the like.  That and scanning for wifi sources and
cross-referencing them against the boat's GPS.  Automagically handling it.
Having to deploy a tripod wouldn't make that very convenient.  I'm planning
on our laptops to connect to just the on-boat SSID and then have the gateway
(either the laptop or the WRT54g) handle the interconnecting to the short
points.

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The wind/waves/speed would probably break the copper center conductor in
pretty short order.

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Some omni have coax from the center, not all.  Some are just a connector
(N-style) on the bottom.  But even the ones with the center wire most
extensions are slotted in some fashion or another to accomodate the wire
exiting from inside for a pigtail going into the deck surface.  Some gymbals
also have similar slots.  So that's no real worry.

My idea about using antennae with N-style connectors is to allow unscrewing
them without pulling cable.  Antennae with center coax pigtails built into
them would be impossible to swap easily.  Something like this:

         |  The N-style antenna
         |
      /-[|]  A z-shaped bracket collared around an extension pipe
  |  /
  +--
 -0-  The usual marine gymbal mount
  |
-------------

Or turn the bracket back in a U-shape over the gymbal to keep the weight
centered.

  |  The N-style antenna
  |
 [|]-+  A U-shaped bracket collared around an extension pipe
     |
  +--+
 -0-  The usual marine gymbal mount
  |
-------------

I'd just need to get the bracket fabricated.  Really not much more than some
sheet metal with the right size holes in it and bended appropriately.  And
then powder or otherwise coated to ward of corrosion.  And it'd also allow
some 'fine tuning' of the angles by slightly bending the bracket.

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Well, if I go with the above ideas on bracketry there ought to be 'enough'
bend radius to accomodate LMR-400.

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Heh, nothing worth doing ever is.

-Bill Kearney


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