I've just bought a new Raymarine radar in the winter sales (hurray!). Can
anybody advise the correct height to mount the scanner on the mast? My mast
height is about 20m.

On Tue, 3 Jan 2006 18:36:26 -0000, "Nicholas Walsh"
wrote:

I've just bought a new Raymarine radar in the winter sales (hurray!). Can
anybody advise the correct height to mount the scanner on the mast? My mast
height is about 20m.

About halfway up seems to be typical, perhaps less in your case since
you have a tall rig. I would try to locate it somewhere above a set
of spreaders to minimize interference with the radiation pattern but
maximize physical support. Minimizing interference with sails is also
important.

Wayne.B wrote:
On Tue, 3 Jan 2006 18:36:26 -0000, "Nicholas Walsh"
wrote:


I've just bought a new Raymarine radar in the winter sales (hurray!). Can
anybody advise the correct height to mount the scanner on the mast? My mast
height is about 20m.


About halfway up seems to be typical, perhaps less in your case since
you have a tall rig. I would try to locate it somewhere above a set
of spreaders to minimize interference with the radiation pattern but
maximize physical support. Minimizing interference with sails is also
important.

Ours is about 20 feet up the mizzen on a gimbled platform and we get no
clutter from the mainmast or sails. It is good out to about 15 miles.

"Nicholas Walsh" wrote in
:

I've just bought a new Raymarine radar in the winter sales (hurray!).
Can anybody advise the correct height to mount the scanner on the
mast? My mast height is about 20m.



First my condolences. I've just replaced ours on "Lionheart" with the
4TH one in 3 years. The condensation INSIDE the radome just eats the
cheap potmetal the radar receiver box is mounted in, rotting all the
unsealed boards inside with copper-to-potmetal electrolysis. Raymarine
has replaced them free....but is this the way to make radars??

As to mounting it, there's a trade. You are a sailboat so nothing
happens very fast. 15 mile range is overkill at 8 knots as you won't be
there for 2 hours, yet. If you mount it high up, you get excellent
range. Sounds good, eh? Unfortunately, high up also has a tradeoff in
how CLOSE to the boat you can see that big, heavy, CG bouy in the
whiteout fog bank. High up, the radar's beam goes OVER the top of low-
down items, like bouys, and the closer they are, the worse they display.
So, I consider putting the radar antenna DOWN much more important to
safety, where the range is only 4-5 miles, but you can see the bouy 12'
in front of the bow just fine in the fog. About 10' off the water, no
more than 15' up is ideal.

Your cheap Raymarine uses a phased array scanner antenna made out of a
cheap piece of printed circuit board just etched with the antenna
phasing elements and stripline matching sections, all on the board. It
has a quite narrow horizontal beamwidth, but a quite wide vertical
beamwidth, which is great for sailboats because this antenna works well
heeled over to 20 degrees without being leveled by some gimbal
mechanism. We had one on a post mounted on the port corner of the stern
on an Endeavour 35 sloop and I could never see any range difference by
tilting the mount to level the antenna, much. The waves offshore are
what screw up the targets on the other side of them....

AIS is gonna fix all this....soon, I hope. Everyone needs a
transponder!....

http://www.aislive.com/
take a look.

This makes almost no sense:
Larry wrote:
"Nicholas Walsh" wrote in
:


As to mounting it, there's a trade. You are a sailboat so nothing
happens very fast. 15 mile range is overkill at 8 knots as you won't be
there for 2 hours, yet.
Of course the RO-RO coming at you at 25 knots gives a closing speed of
33 knots or 3.3 miles every 6 minutes. He'll be on top of you in 15
minutes. Navigating, 15 miles off shore with radar fixes is nice when
your GPS fails.
If you mount it high up, you get excellent
range. Sounds good, eh? Unfortunately, high up also has a tradeoff in
how CLOSE to the boat you can see that big, heavy, CG bouy in the
whiteout fog bank.
Not!
High up, the radar's beam goes OVER the top of low-
down items, like bouys, and the closer they are, the worse they display.
So, I consider putting the radar antenna DOWN much more important to
safety, where the range is only 4-5 miles, but you can see the bouy 12'
in front of the bow just fine in the fog. About 10' off the water, no
more than 15' up is ideal.
So why do ships have theirs up on top of the bridge? Because the radar
is built with fairly wide vertical beams. You won't be able to get it
high enough that you can't see seagulls directly in front of you. In
addition, the pitch of the boat will have a greater negative effect than
putting the radar at the best height you can manage.

Your cheap Raymarine uses a phased array scanner antenna made out of a
cheap piece of printed circuit board just etched with the antenna
phasing elements and stripline matching sections, all on the board.
Not phased array. Check their website
http://www.raymarine.com/raymarine/D...age=4&Parent=2
Phased array scanners are not cheap or common. They are exceptional.
Check it: http://en.wikipedia.org/wiki/Phased_array

It
has a quite narrow horizontal beamwidth, but a quite wide vertical
beamwidth, which is great for sailboats because this antenna works well
heeled over to 20 degrees without being leveled by some gimbal
mechanism.
If it was phased array, none of this would matter but it's not. Look it
up. The horizontal beam is about 5 degrees (for target separation) and
the vertical about 25 degrees (to account for pitching and mounting
height). Nothing to do with rolling.

We had one on a post mounted on the port corner of the stern
on an Endeavour 35 sloop and I could never see any range difference by
tilting the mount to level the antenna, much. The waves offshore are
what screw up the targets on the other side of them....
Hence the need to mount it higher than lower.

AIS is gonna fix all this....soon, I hope. Everyone needs a
transponder!....
And a receiver. But that won't help you spot logs, containers or other
flotsam and jetsam.

http://www.aislive.com/
take a look.

This is generally the worst advice ever. You should do some research
and talk to the guys in the shop.

I would put the dome at a strong point as high on the mast as stability
and common sense would allow. I am not an expert on radar mounting but
I use them daily in my job as a ship's master. I wish I had one on my
own sloop.

Gaz

On Tue, 03 Jan 2006 19:00:57 -0500, Larry wrote:

As to mounting it, there's a trade. You are a sailboat so nothing
happens very fast. 15 mile range is overkill at 8 knots as you won't be
there for 2 hours, yet. If you mount it high up, you get excellent
range. Sounds good, eh? Unfortunately, high up also has a tradeoff in
how CLOSE to the boat you can see that big, heavy, CG bouy in the
whiteout fog bank. High up, the radar's beam goes OVER the top of low-
down items, like bouys, and the closer they are, the worse they display.

================================================== ===

I disagree with this premise based on my own experience. I have a 2
KW Furuno mounted 24 feet above the water. It has absolutely no
problem seeing near by targets, right down to the limitation of the
electronics which is about 50 feet. We were out the other day and it
picked up a duck sitting on the water about 100 feet in front of us.

As far as a sailboat not needing anything past 15 miles because of
slow speed, that is a dangerous assumption. A commercial ship
traveling at a typical offshore speed of 20 kts is moving 1 nautical
mile every 3 minutes. If you are converging from opposite directions
at 8 knots, even faster. I like all the warning time I can get, and
being able to pick up distant shore features is desirable also.

Larry,
You brought up a good point, but your reasoning is incorrect. All marine
scanners have a 30 degree verticle radiation pattern, This is too compensate
for roll and heel. So, radiating a target dead in front is not an issue. The
restriction at close range is Pulse width and receiver turn on time. A RADAR
mile is 6.36 micro seconds. If you want to see a target 100 yards in front,
the RADAR set must transmit a pulse and turn on the receiver to catch the
echo in less than .31 micro seconds. That's a very tall order with a
magnetron, as they are not gated. They operate by dumping high voltage on
the cathode, which rings the hell out of the cavity. They turn off when the
cavity decides it no longer is excited and the receiver can not turn on
until there is no more energy being emitted from the magnetron. This is
becoming a very big issue in Europe at the moment. There now is a new
commercial regulation as of Jan. '06 specifically pointed at canal traffic
that stipulates that all new RADAR sets work at 50 meters. For exactly the
reason you mentioned in your post. Now that's tough to do.
Steve

"Larry" wrote in message
...
"Nicholas Walsh" wrote in
:

I've just bought a new Raymarine radar in the winter sales (hurray!).
Can anybody advise the correct height to mount the scanner on the
mast? My mast height is about 20m.



First my condolences. I've just replaced ours on "Lionheart" with the
4TH one in 3 years. The condensation INSIDE the radome just eats the
cheap potmetal the radar receiver box is mounted in, rotting all the
unsealed boards inside with copper-to-potmetal electrolysis. Raymarine
has replaced them free....but is this the way to make radars??

As to mounting it, there's a trade. You are a sailboat so nothing
happens very fast. 15 mile range is overkill at 8 knots as you won't be
there for 2 hours, yet. If you mount it high up, you get excellent
range. Sounds good, eh? Unfortunately, high up also has a tradeoff in
how CLOSE to the boat you can see that big, heavy, CG bouy in the
whiteout fog bank. High up, the radar's beam goes OVER the top of low-
down items, like bouys, and the closer they are, the worse they display.
So, I consider putting the radar antenna DOWN much more important to
safety, where the range is only 4-5 miles, but you can see the bouy 12'
in front of the bow just fine in the fog. About 10' off the water, no
more than 15' up is ideal.

Your cheap Raymarine uses a phased array scanner antenna made out of a
cheap piece of printed circuit board just etched with the antenna
phasing elements and stripline matching sections, all on the board. It
has a quite narrow horizontal beamwidth, but a quite wide vertical
beamwidth, which is great for sailboats because this antenna works well
heeled over to 20 degrees without being leveled by some gimbal
mechanism. We had one on a post mounted on the port corner of the stern
on an Endeavour 35 sloop and I could never see any range difference by
tilting the mount to level the antenna, much. The waves offshore are
what screw up the targets on the other side of them....

AIS is gonna fix all this....soon, I hope. Everyone needs a
transponder!....

http://www.aislive.com/
take a look.

Wayne,
50 feet? I don't think so. Check the transmitter specs and do the math.
Lamda = 3.18 u sec per mile, one way.
Steve


"Wayne.B" wrote in message
...
On Tue, 03 Jan 2006 19:00:57 -0500, Larry wrote:

As to mounting it, there's a trade. You are a sailboat so nothing
happens very fast. 15 mile range is overkill at 8 knots as you won't be
there for 2 hours, yet. If you mount it high up, you get excellent
range. Sounds good, eh? Unfortunately, high up also has a tradeoff in
how CLOSE to the boat you can see that big, heavy, CG bouy in the
whiteout fog bank. High up, the radar's beam goes OVER the top of low-
down items, like bouys, and the closer they are, the worse they display.

================================================== ===

I disagree with this premise based on my own experience. I have a 2
KW Furuno mounted 24 feet above the water. It has absolutely no
problem seeing near by targets, right down to the limitation of the
electronics which is about 50 feet. We were out the other day and it
picked up a duck sitting on the water about 100 feet in front of us.

As far as a sailboat not needing anything past 15 miles because of
slow speed, that is a dangerous assumption. A commercial ship
traveling at a typical offshore speed of 20 kts is moving 1 nautical
mile every 3 minutes. If you are converging from opposite directions
at 8 knots, even faster. I like all the warning time I can get, and
being able to pick up distant shore features is desirable also.

I was perusing the Yamaha online parts catalog and found the
following:

http://tinyurl.com/an2q6

"All these models use the same part catalog. Be sure to
order only those parts applicable to the desired model.

9.9 MSH (63V5 - Yamaha part code)
15 MSH (63W5 " )

The only difference between the 2 stroke 9.9 and 15 models
that I found was the intake reed valve assembly. They have
different part numbers. Everything else that I checked was
the exact same part number.


Here's the link to the two different parts catalogs (see
"Intake" for the reed valve assembly, one identifed with 63V
and the other with 63W.

http://tinyurl.com/7lpth for the 15 HP

http://tinyurl.com/aaahk for the 9.9 HP


Both have the same carb, pistons, and anything else I could
think of. I have always heard that there is usually little
difference between 9.9 and 15's; 6 & 8's etc. but I was a
little bemused to find that such a simple swap could
potentially save me a lot of cash by buying a 9.9 and a 15's
$41 reed valve assembly. Could it be that simple? There's
about a $400 difference in the retail price by the way.


What I *really* want is a Yamaha 15 ENDURO, but they aren't
found in Canada or the US. If anybody has a line on one in
Mexico or the Bahamas and some suggestions on getting it
into Canada or the US, let me know.

Evan Gatehouse

In article ,
"Steve Lusardi" wrote:

All marine scanners have a 30 degree verticle radiation pattern,

Well not quite "ALL"....actually the Furuno Spec is 25 Degrees, and has
been for Years....

Me