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Old 08-29-2011, 09:25 AM   #1
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Radar questions

A few naive questions:

1). The range stated is more limited by the Radar height above water du to the earths curvature, correct? Without getting out my ancient trigonometry memories, the distance to horizon at the water level is only 7 statute miles correct?

2). Can the higher power radars see more detail closer in? Do the larger open arrays see more detail?

Which brings me to my sort of related question...

For a single control station boat, what would you consider a minimum, with excellent redundancy set up?

From my reading:
Integrated GPS/radar/chart plotter/depth sounder
Separate GPS/possibly a hand held with external antenna
Laptop that uses the above gps fo navigation
Separate depth sounder
2 VHF radios with separate antenna systems, plus a handheld VHF in a ditch bag
Automatic EPIRB
MOB alarms on the kids

Is adequate/too much for inside passage to Alaska?
paper charts
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Old 08-29-2011, 09:50 AM   #2
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RE: Radar questions

I would suggest you start here,

http://www.furunousa.com/Learning%20...arGuide-LR.pdf

*

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Old 08-29-2011, 01:46 PM   #3
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Radar questions

Range is determined by both power and antenna height. As a generality, the wider the antenna the more detail the radar will be able to discern. Open array does not automatically mean more detail--- it's just that open array antennas can be larger which in turn can enhance detail. A radome limits the practical width of a radar antenna. Also, some boats, particulary sailboats, can't accomodate an open array antenna as the boat's rigging could get caught up in it.

Which attributes are best for the radar on your own boat depends on several factors. How far do you need to see? Where we boat, for example, there are tons of islands and few large bodies of open water. Most of the time we're not going to see visually more than five or ten miles before an island gets in the way. So a radar with a range of 36 miles or so is more than sufficient for these waters in our opinion.

What are you most concerned with seeing? For us, it's relatively close-in things. Crab pot floats, fishing boats, etc. We're not looking for that 30 knot bulk carrier just over the horizon. So we want good detail, but for the most part we want it fairly close to the boat. Other people cruising more open water would probably want to see farther with more detail out farther.

For us, the Furuno NavNet VX2 was ideal for our boat and the way we use it. We bought it with a 24" antenna in a radome. The same unit is available with an even smaller antenna in a radome, or various sizes of larger open array antennas. The 24" antenna also fits nicely on our existing antenna mount.

Furuno still makes this unit but they have since come out with NavNet 3D. I have not seen nor had any experience with NavNet 3D.

While our boat has a flying bridge helm station we never use it. We always run from the lower helm. It is equipped with an older Ecotech GPS chart plotter (green screen), the newer Furuno NavNet*VX2 wich has radar and GPS plotter functions (we did not get the depth sounder option), an Icom VHF radio, a Standard Horizon loud hailer/intercom, a combination depth/trip log/time display, and a now-useless Furuno Loran-C unit. Having two GPS plotters at the helm is handy. We run one on map display and the other screen is usually*split between radar and a heading-course-steering-time to go, etc. display. All our plotters use C-Map cartography.

We also have an Icom handheld VHF and a Standard Horizon GPS we recently bought for our smaller boat that can be mounted on the flying bridge of the GB should we have guests riding up there who want to see where we are.

Whatever you end up getting, I suggest the larger the display screen you can afford and accomodate the better.* And bear in mind that whatever claims Furuno might make for their NavNet displays being "daylight visible," they kind of aren't.* One advantage of the Standard Horizon plotter we recently bought is it's suprisingly bright screen, which is what we need for our small fishing boat.

I've posted this photo before but this is our lower helm layout.* In the photo the Furuno is displaying the chart only.* We normally have it on either radar only or split between the radar and steering information.* Also the Icom*VHF in the photo has recently been changed out for a newer Icom model.

A really good book on radar and how to get the most out of it is Kevin Monohan's "The Radar Book.


-- Edited by Marin on Monday 29th of August 2011 06:44:51 PM
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Old 08-30-2011, 07:02 AM   #4
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RE: Radar questions

"For radar power, minimum 4 kw. Smaller power can't punch through rain and snow as well."

*

Perhaps, but I have a 2 kw Furuno and it works fine for me. It does all I want it to do. Most of the time I have it on 2 mile range or less as I rarely care what's past that unless I am trying to find a tx storm.
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Old 08-30-2011, 08:18 AM   #5
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RE: Radar questions

Does a higher transmit power equate to "seeing" smaller objects closer?

Would a 6KW see a floating object at 2-4 miles out than a 2KW?

Does the open array help with that situation also?

Other than redundancy, is their any benefit to splitting out devices (separate depth sounder etc)?

The Furuno website was an excellent resource thanks. They also have an good selection of videos on their website.

I am experienced public safety radio tech. Height above the water would seem to me to be the biggest benefit.... to a point.
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Old 08-30-2011, 09:02 AM   #6
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RE: Radar questions

Radar height*discussions should take into account the targets too. When boating in the PNW the mountains are wonderful targets for navigation purposes. Ships and* ferries easily show up 8 -12 miles away on my Furuno. On a 20 knot vessel (not for us on this Forum) targets 4 to 6 miles out become important as does the quality of the radar system. Layering AIS targets on the radar screen is effective too.

Redundant systems are great IMHO. I have 4 different GPSs, 3 depth sounders and 3*charplotters.*Then adding in the handhelds the count goes up. My first crossing of Georgia Strait and Juan de Fuca 40 years ago was without any instruments except a compass. Weather prediction was based upon how many flags were flying at the marinas. It is sure easier and safer today
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Old 08-30-2011, 12:09 PM   #7
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RE: Radar questions

Quote:
Badger wrote:
Height above the water would seem to me to be the biggest benefit.... to a point.
Don't get too hung up on height.* In some cases a lower antenna is better.* A specific example is up here where stuff in the water like crab pot floats can be a major factor in one's naviagation.* The higher the radar antenna, the farther out from the boat it will begin to see returns.* Mount an antenna too high and you'll miss that close-in stuff that could ruin your day if it gets caught up in your running gear.

The height of the antenna should be governed by what you feel is most important to "see."
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Old 08-30-2011, 12:13 PM   #8
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RE: Radar questions

Quote:
Marin wrote:Badger wrote:
Height above the water would seem to me to be the biggest benefit.... to a point.
Don't get too hung up on height.* In some cases a lower antenna is better.* A specific example is up here where stuff in the water like crab pot floats can be a major factor in one's naviagation.* The higher the radar antenna, the farther out from the boat it will begin to see returns.* Mount an antenna too high and you'll miss that close-in stuff that could ruin your day if it gets caught up in your running gear.

The height of the antenna should be governed by what you feel is most important to "see."

*Thats a great clarification and something I need to know!

*

Easy to see the islands/land masses, harder to see the pots and logs
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Old 08-30-2011, 02:21 PM   #9
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RE: Radar questions

Quote:
Badger wrote:Easy to see the islands/land masses, harder to see the pots and logs
Don't know about logs.* Most of the commercial crab pot floats around here have big metal fender washers as part of their lashup.* So there's somethingt there to reflect the radar transmission.
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Old 08-31-2011, 10:51 AM   #10
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RE: Radar questions

Quote:
Badger wrote:Marin wrote:Badger wrote:
Height above the water would seem to me to be the biggest benefit.... to a point.
Don't get too hung up on height.* In some cases a lower antenna is better.* A specific example is up here where stuff in the water like crab pot floats can be a major factor in one's naviagation.* The higher the radar antenna, the farther out from the boat it will begin to see returns.* Mount an antenna too high and you'll miss that close-in stuff that could ruin your day if it gets caught up in your running gear.

The height of the antenna should be governed by what you feel is most important to "see."

*Thats a great clarification and something I need to know!

*

Easy to see the islands/land masses, harder to see the pots and logs

*Our 4 KW Furuno radar is about 17' above the waterline and very slightly canted down. I've noticed that logs often show up as small blips although with any kind of seas they disappear into the clutter. As does the prodigious wake that shows up at 7.5 knots...

According to our dealer, you should stay about 10' away from the direct beam of the 4 KW antenna and its 20 degree vertical beam. With that in mind we positioned our antenna so our our 6'4" son in law could stand at the upper helm and not get nuked. Gotta look out for those grandchildren!*
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Old 08-31-2011, 12:21 PM   #11
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RE: Radar questions

Quote:
Conrad wrote:According to our dealer, you should stay about 10' away from the direct beam of the 4 KW antenna and its 20 degree vertical beam. With that in mind we positioned our antenna so our our 6'4" son in law could stand at the upper helm and not get nuked. Gotta look out for those grandchildren!*
It's certainly better to be safe than sorry, but the information I've been given by both our electronics dealer and people here at Boeing who deal with radar is that the only way you could cause any damage to yourself with a modern radar of the type used on most recreational boats is by holding your head hard up against the radome for a solid week with the radar on and transmitting.

That said, we turn off our radar if someone wants to ride up on the flying bridge during a cruise.* Like many older boats with solid wood masts, our boat has a flying bridge face mount for the radar antenna.* This has two advantages and a whole lot more disadvantages.* I would never recommend mounting a radar antenna in this position and it baffles me why some new-boat manufacturers still do it, the Camano Troll being an example that springs to mind.

But the transmission signal of the kinds of radars we're talking about here are apparently nothing to be concerned about.* But..... better safe than sorry :-)
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Old 08-31-2011, 10:51 PM   #12
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RE: Radar questions

third generation radars - such as the Simrad BR24-3G - would be much better for close in navigation (less than 6nm) - but at the expense of distance, bird and weather detection capabilities.
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Old 09-01-2011, 08:34 AM   #13
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RE: Radar questions

Quote:
Singleprop wrote:
third generation radars - such as the Simrad BR24-3G - would be much better for close in navigation (less than 6nm) - but at the expense of distance, bird and weather detection capabilities.
*Just a little reading and it seems to be an ideal setup to have the Simrad and a high power as a long range tool..* albeit more $$$
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Old 09-01-2011, 08:45 AM   #14
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RE: Radar questions

On most newer digital*units you can run a split screen for short and long distance. My NN3 is that way. If contemplating a redundant system, consider broadband.
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Old 09-05-2011, 06:48 AM   #15
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RE: Radar questions

"...our boat has a flying bridge face mount for the radar antenna. This has two advantages and a whole lot more disadvantages"

And the list of these advantages/disadvantages might look like what?

Thanks.
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Old 09-05-2011, 09:42 AM   #16
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RE: Radar questions

I would add an*AIS receiver to your basic list.* We use Coastal Explorer and the AIS targets are displayed with the vessel names and a vector line with the*predicted course.* I can click the target and get basic size, speed and heading info.* There is also closest point of approach, time to approach, etc data.* I use this to learn more about a radar or visual target.* While in the Northwest, it was a great help identifying traffic before they popped*out from behind an island.* I expect that all modern plotters will display AIS data.*

We use a small format Furuno 7000F chartplotter/fishfinder from 2007.* If they still make a comparable unit, you might use this as your primary depth unit and have a back up chart plotter as a bonus.

Lastly,*I went on the internet and downloaded all the ferry schedules for our cruising area.* I kept these pdf's on the desktop and would check my route the night before as we frequently were departing from or arriving at ferry stops.* We could adjust our plans by 15 or 30 minutes to avoid close encounters of the ferry kind.
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Old 09-06-2011, 04:47 PM   #17
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Radar questions

Quote:
dvd wrote:
"...our boat has a flying bridge face mount for the radar antenna. This has two advantages and a whole lot more disadvantages"

And the list of these advantages/disadvantages might look like what?

*One advantage is that with the radar antenna the low stuff on the water very close to the bow shows up.* This has proven extremely helpful on a few occasions when we've been in heavy fog in an area that had been planted with lots of commercial crab pots.* Their floats generally incorporate a big fender washer for some reason so they actually send out a really good return if the transmitted beam hits them.

Second advantage is that having the radar antenna on the face of the flying bridge makes it REALLY easy to run the cable to the display unit.* In our case, with the display unit in a retractable mount in the overhead above the lower helm station the cable comes out of the antenna, runs*through*the center*mount tube to the inside the flying bridge console and straight into the box housing the retractable mount.* The rest of the 30' cable is simply coiled up under the flying bridge console.

Disadvantages....

1.* The llower antenna height could restrict range if that's important to where you boat (it's not to us here).*

2.* Depending on the construction of your boat, this antenna position can mask signal transmissions and returns aft of the boat.* In our case there are engine instruments, throttle, shifter, and cable steering mechansm hardware beind the antenna and level with it.* So we don't get much in the way of returns from directly behind the boat.* We'll see something big like*a ferry but other boats our size and smaller don't generally show up well or at all.*

3.* It would be possible to raise a radar*antenna on*a flying bridge face mount using a tower or some other contrivance, but then it would block visibility if one steered from up there.*

4.* There is the health issue of having an antenna in this position if people are going to be riding up top when the radar needs to be on.* As mentioned previously, we've been told by several sources that the transmissions from the typical modern radar of the type most of use on our boats is a minimal to zero health risk but better safe than sorry, right?*

5.* Finally, these flying bridge face mounts can be pretty ugly if you care about such things.* The one on our boat (which was there when we bought it) is actually one of the best I've seen but I have seen some that are truly awkward or*kluged together and it can make an otherwise good looking boat look kind of crappy.

While it's not high on our to-do list we'd like to move the radar antenna to the mast someday.* But it's not a problem as it is now.* But if someone was going to mount a radar on a boat that doesn't have a radar now, I would never recommend a flybridge face mount.* The downside outweighs the upside in my opinion.* Put the antenna on a mast or arch, but not on the flying bridge face.


-- Edited by Marin on Tuesday 6th of September 2011 04:48:17 PM
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Old 09-11-2011, 05:08 PM   #18
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RE: Radar questions

On my sailboat I have broadband radar. its good for up close and uses half of the electricity. It is also safe to mount near people. I single hand on long crossings so it and my ais transponder are great to have.
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