radar-open or closed?

[magna 6882]

I have read that open units provide a tighter signal.What are your thoughts regarding open or closed.

 

[twistedtree]

"Tight" isn't quite the right word, but what you get from a wider antenna is a narrower horizontal width to the beam. A 24" dome may have a horizontal beam width of 2-3 deg where an 8' antenna will be less than 1 deg.


Why does it matter? Because the radar can't tell the difference between one target and two (or more) when they are within the beam width, and at the same distance. And the further away the targets are, the further apart they can be and still look like one target. The radar's output is also concentrated into a narrower beam, so has more effective power.


If you have room and don't mind the extra cost, I'd install the largest open array that's practical. But if what's practical is a dome, I wouldn't lose any sleep over it, or feel inferior in any way. It will do the job just fine.

 

[High Wire]

This ^^^. Bigger is better when talking radar antennas. Now 24" dome or 24" open array??? If you can get a MARPA equipped unit, go for it.

 

[rslifkin]

Twistedtree covered it well. Big open arrays will have better target separation, particularly at longer distances. They often have a longer maximum range as well.

Depending on the boat and mounting location, weight can be a concern. As an example, the 24" Furuno NXT dome is about 16 lbs. The 3.5 foot open array version is just over 48 lbs, and the 6 foot open array is almost 60 lbs.

Open arrays also tend to use more power (even if output power is the same), especially to keep things spinning at the right speed in high winds.

Oh, and there's another difference. Price. Looking at one source, a that Furuno NXT dome is about $2100, while the basic 25w base for the open arrays is $3700 (no price on the 100W or 200W base yet, they're too new). And then another $750 - 1400 for the antenna, depending on 3.5, 4, or 6 feet. So even a 3.5 foot open array is over twice the price of the dome.

 

[psneeld]

Most people neither need or ever become proficient enough to need more than a 4kw dome.

That said....if you use the boat a lot, the radar isn't going to cost 25% of the boats worth, the boat is big enough to handle it, and you actually learn to use it....then the sky is the limit in terms of what you buy.

But in my experience, 95% of rec boaters (without pro experience) never need much more than a basic 4kw dome or a broadband equivalent.

 

[caltexflanc]

I would amend that to say "never will bother to learn to use".

If one never ventures outside into the ocean, nor has occasion to boat in limited-to-no visibility conditions then I'd have to agree that a modern dome is just fine. That's what I learned on and used on our various charters, which were all nearshore/ inshore. But I sure noticed the difference when I bought a boat with a Furuno open array.

 

[tiltrider1]

Most people neither need or ever become proficient enough to need more than a 4kw dome.

That said....if you use the boat a lot, the radar isn't going to cost 25% of the boats worth, the boat is big enough to handle it, and you actually learn to use it....then the sky is the limit in terms of what you buy.

But in my experience, 95% of rec boaters (without pro experience) never need much more than a basic 4kw dome or a broadband equivalent.

I’m with psneeld. Most boaters don’t need more than 4kw and most don’t need more than an 18” array. In the PNW most boaters are operating between 1/8 and 3 miles range. At that distance only the experts can tell the difference between an 18” and a 48” array. At 3 miles you might not be able to tell if it’s 1 kayak or two with an 18” array but at 1.5 mile you will.

One should buy the array that fits and if they have the money there is always some gain in going larger but don’t break the bank.

 

[psneeld]

Noticing the difference and proficiently using it are 2 different things.

After teaching hundreds of boaters including charter boat captains upgrading....most rec boaters barely need radar, let alone ever be really comfortable or proficient with it.

I did see a big difference in the 4kw vs 2kw years ago...but that may have changed and broadband is a whole new world.

 

[mvweebles]

Last year I went through the selection process when my old Furuno CRT with 24" magentron dome died. I plan on cruising the boat, and I am generally a radar guy so it's important to me. I first started looking at open arrays for the reasons TT notes. But their high cost ----- and the relative low cost of digital arrays ---- got me thinking. In the end, I opted for a Simrad 4G radar/MFD system, though there are others. For the life of me I just could not think of a use-case where I needed the additional range and definition of a larger antenna. And digital/broadband systems are reportedly better at close-in targets such as smaller, private mooring balls.

Quality of lower-end systems have improved immensely and price points have gone down dramatically and more features have been packed in.

Peter

 

[Codger2]

For the life of me I just could not think of a use-case where I needed the additional range and definition of a larger antenna.

I have been able to pick up large flocks of feeding sea birds on my open array antenna where I couldn't on my old dome antenna. It's definitely an advantage when looking for fish.

 

[Alaskan Sea-Duction]

When I upgraded ASD, I had the same questions as the OP. I was replacing an old, but still good open array from Ratheon. The green dot. I talked to lots of boaters and professionals. The furthest offshore I would be go maybe 30 miles. Most of the time it would be used in limited viability near the coast or inland waters.

I didn't need a super radar that the big ships carry, nor did I want the cost. So I went with a closed array good out to 40 miles. I also chose Raymarine as that was the system I was using, thus easy to install. Staying within the family.

My $0.02

 

[mvweebles]

I have been able to pick up large flocks of feeding sea birds on my open array antenna where I couldn't on my old dome antenna. It's definitely an advantage when looking for fish.

Good tip, though I confess I am the world's worst fisherman. I can't tell you how many times I've gone out on someone's boat only to return with the same old "Jeez, fishing is never that bad" story. Fortunately, Publix (Florida supermarket chain) makes a fantastic batch of fried chicken fingers. Great day-trip food on the water.

Seriously, I know the big open arrays are great. I see Codger is out of SoCal - I used to go in/out of Ventura once or twice a year. With a good radar, I could pick-up small aircraft landing at a nearby executive airport from 15+ miles away. Kind of scared me first time I saw it until I figured it out.

Peter

 

[rsn48]

The new broadband radar is better than older radars and even with range the performance is better than in the past. I will just give you a copy and paste:

Solid-state, broadband radar sends a continuous transmission wave with linearly increasing frequency (hence the term broadband). The wave retains its frequency as it travels out and reflects back from any objects. Meanwhile, the transmitter continues to output an increasing frequency. The difference between the currently transmitted and received frequencies, coupled with the known rate of frequency increase, is the basis for precisely calculating a “time of flight” and target distance. Since FMCW constantly builds up radar return energy (vs. a single “main bang” pulse), this system provides target detection superior to pulse radars while transmitting at far lower energy levels.

Simrad broadband 4g radome mounted at the helm of a boat
Simrad Broadband 4G™ Radar

Solid-state radar offers the following advantages over traditional pulse radar:

Lowest RF transmission for safe, flexible installation: solid-state radar transmits at a very low power level. For example, Navico’s Broadband 4G Radar emits less radiation than an average cell phone, so the radome is safe to mount in locations never before possible. In addition, the lowest DC power draw of any X-band marine radar (1.45 amps) makes this system well suited for sailboats and other vessels with limited power. Even the most powerful solid-state open array radars, the Garmin Fantom™, transmit at 40 watts, compared with 4,000 watts for a small traditional pulse radar.
Improved short-range target discrimination: solid-state radar provides better target resolution, even at an amazingly close 1/32 nm range. Docks, channel markers, moored vessels and other critical targets are displayed with clarity and separation, for added confidence in close quarters. Solid-state, broadband technology also eliminates the “main bang” of a pulse radar—the obscured “dead zone” immediately around the vessel—which interferes with close target detection.
No warm-up time: no more waiting 2-3 minutes for a magnetron to warm up. When darkness falls or the fog rolls in, you are always ready. Ideal for sailboats wishing to save power or boats at anchor not wishing to run the radar continuously.
Maximum range that’s comparable to conventional pulse radar: Although broadband radar used to be inferior to the old-school high-powered technology outside the three-mile range or so, they’re closing the gap. Navico has mitigated this problem with their 3G radar, doubling the transmitting power of the original BR-24, and increasing the range by 30 percent, to 24 nautical miles. Their Broadband 4G™ radar narrows the gap even more, with a maximum range of 36 nautical miles. It also uses unique “beam sharpening” to further boost its effective range. Simrad’s Halo™-6 open array is now listed as a 72 nautical mile radar.

 

[Jon H]

Seldom was the radar range above 24 NM on any ship I sailed on.

When making landfall at the end of an ocean passage it might get bumped
up to 48 NM just to pick up land earlier.


Large open array antenna are very good at target discrimination -
picking up small items like birds on water if you fish, logs floating on water, etc.


I have a Garmin 24xHD on my boat, it works very well and has great target
resolution, I typically use it in the 0.5 to 3 NM ranges - usually in fog.

 

[O C Diver]

Had both an open and a closed Furuno on my charter boat. While I did practice with the closed unit, a dialed in open with a 4' antenna was clearly superior. Mine runs whenever the boat is underway, so lots of practice. The other nice feature of the more powerful open unit is to watch weather front storms coming when way offshore.

On the trawler I put a 6 KW 6' open array in anticipation of crossing the Great Lakes and the Gulf of Mexico. For most of the AICW and near coastal cruising I do, the largest dome would probably have been fine.

Ted

 

[Nomad Willy]

I suspect the’d all be closed if the antenna was’nt so large.

 

[JDCAVE]

The new broadband radar is better than older radars and even with range the performance is better than in the past. I will just give you a copy and paste:

Solid-state, broadband radar sends a continuous transmission wave with linearly increasing frequency (hence the term broadband). The wave retains its frequency as it travels out and reflects back from any objects. Meanwhile, the transmitter continues to output an increasing frequency. The difference between the currently transmitted and received frequencies, coupled with the known rate of frequency increase, is the basis for precisely calculating a “time of flight” and target distance. Since FMCW constantly builds up radar return energy (vs. a single “main bang” pulse), this system provides target detection superior to pulse radars while transmitting at far lower energy levels.

Simrad broadband 4g radome mounted at the helm of a boat
Simrad Broadband 4G[emoji769] Radar

Solid-state radar offers the following advantages over traditional pulse radar:

Lowest RF transmission for safe, flexible installation: solid-state radar transmits at a very low power level. For example, Navico’s Broadband 4G Radar emits less radiation than an average cell phone, so the radome is safe to mount in locations never before possible. In addition, the lowest DC power draw of any X-band marine radar (1.45 amps) makes this system well suited for sailboats and other vessels with limited power. Even the most powerful solid-state open array radars, the Garmin Fantom[emoji769], transmit at 40 watts, compared with 4,000 watts for a small traditional pulse radar.
Improved short-range target discrimination: solid-state radar provides better target resolution, even at an amazingly close 1/32 nm range. Docks, channel markers, moored vessels and other critical targets are displayed with clarity and separation, for added confidence in close quarters. Solid-state, broadband technology also eliminates the “main bang” of a pulse radar—the obscured “dead zone” immediately around the vessel—which interferes with close target detection.
No warm-up time: no more waiting 2-3 minutes for a magnetron to warm up. When darkness falls or the fog rolls in, you are always ready. Ideal for sailboats wishing to save power or boats at anchor not wishing to run the radar continuously.
Maximum range that’s comparable to conventional pulse radar: Although broadband radar used to be inferior to the old-school high-powered technology outside the three-mile range or so, they’re closing the gap. Navico has mitigated this problem with their 3G radar, doubling the transmitting power of the original BR-24, and increasing the range by 30 percent, to 24 nautical miles. Their Broadband 4G[emoji769] radar narrows the gap even more, with a maximum range of 36 nautical miles. It also uses unique “beam sharpening” to further boost its effective range. Simrad’s Halo[emoji769]-6 open array is now listed as a 72 nautical mile radar.

Is that science or advertising?

I see lots of misinformation on echosounders in the advertising departments in the yachting world. I asked Simrad’s sales team to provide information on the beam width and transducer mapping of one of their units and got no reply. I think the science went right over their heads.

TT is correct: narrower beam width = greater resolution. Radar as well as hydroacoustics.

Jim

 

[rblades]

I have to say being a ATP airline type rate pilot would hardly ever leave without my it working my issue with most is that I have no tilt control which just drives me up the wall.

 

[Comodave]

We have a 4K 24” dome on our current boat. It works fine but I would like a 48” open array. Just couldn’t see the extra expense. We run ours whenever we are underway. I think that the best thing you can do is use the radar extensively so you will get good at interpreting the display.

 

[psneeld]

I have to say being a ATP airline type rate pilot would hardly ever leave without my it working my issue with most is that I have no tilt control which just drives me up the wall.

Flying and boating have similarities....but are completely different in some.

Tilt control on marine radar?

5000 hrs and ATP rated USCG helo time and I NEVER have even thought of why I needed tilt on a marine radar if it was mounted correctly for the boat it was on.

Too many people I know think more than Radar basics make them safe when they have so many other options that would actually work better really amazes me.

Flying IFR is significantly different than low vis radar nav. On the water there are so many things that you may never see on Radar that you can see visually....your boating visual scan in low vis better be much better than IFR flying.

In the last 40,000 miles of Atlantic ICW time....I probably have a couple dozen times that Radar is necessary. For those times of night running, Radar helped but wasn't really necessary.

Is Radar a good thing? You bet! But one step above the basic ones is usually more than most people need.

 

[rslifkin]

Psneeld's logic is why I figure one of the good modern 24" domes will be adequate when I add radar at some point (something like Simrad Halo or Furuno NXT). Yeah, a 4 or 6 foot open array would be nice, but considering I grew up boating without radar and have found it pretty easy to avoid situations where it's more than "nice to have", I expect it'll be very rare to encounter a situation where the better (and more than twice as expensive) radar offers me a meaningful advantage to justify the extra cost, weight, etc.

 

[Alaskan Sea-Duction]

Well the one good thing about an open array:

IT LOOKS SO COOL!!!!

 

[magna 6882]

Well the one good thing about an open array:

IT LOOKS SO COOL!!!!

That was really what motivated me to ask the question. All things being equal it looks cool turning around but am not sure i would pay much more for the effect. They are set to install a 24in furuno dome on a sea king mount.

 

[psneeld]

If you have to look cool .........hmmmmm. ...

Too many barely can dock but that big ole array is still spinning at the dock.....they look cool till the guy in the 35 lobster boat slides it in with 5 inches either side, single, no thruster, wimpy dome. He/she becomes the cool one.

After that no one even notices you have an open array till after dark and everyone reminds you your radar is still on.

 

[OldDan1943]

RADAR can see to the horizon and that is dictated on the height of the antenna.
I had an old 48 mile RADAR on my N46, yup tubes and all. Worked fine but based upon antenna height it too could only see to the horizon. It was sensitive.... I could lower the beam and a separated control for raising the beam.
So basically, it would widen the beam or narrow the beam.
My AT34 has a 24mile enclosed RADAR. I can adjust the beam up and down. It is called "sea clutter".
The important thing to remember is, the RADAR distance is limited to the horizon and that is controlled by the height of the antenna.

 

[rsn48]

How and why folks use radar is really location dependent. I used to ride a road bike all over Chicago back in the late 60's, piece of cake. When I moved to Vancouver using the same bike, not so much. In greater Vancouver you are better off with some lower gears, trust me on this. I know some jerk ... is going to come on and say he/she rides a bike with one gear, if that's the case I will invite them to ride the Mount Seymour Mountain bike race; it only goes in one direction - up.

On other discussions here at TF, others and I have said the main purpose of our radar is to know what is coming up behind us. To actually have the radar tell us what's in front is kind of like a great option but not used that much. I'm more concerned with sports fisherman coming up behind me with their two or three outboard power blaster, planing over the water heading out or heading home. They come up fast and I rely more on the Garmin Fantom radar tracker than I do on my own eyes.

Also the location really matters as to what you need. So if you are a boater in the Puget Sound area up to southern Alaska, including the "inside passage" area of BC, your radars ability to see 45 miles is lost, the radar view blocked by an island or two or three. The radar could see far up into the sound if leaving Seattle heading North, but realistically so what. If you are a Tuna sports fisher out there in the Big Pond, out a fair way from the mainland, having radar pick up distance weather would be a real asset.

This link is a boater demonstrating his 18 inch Garmin Fantom radar, you will notice roughly after the one minute twenty second mark of the video his radar shows a red target behind him, the red tells him that that this target is on a possible collision course with him. I haven't watched the whole video but he doesn't seem to pick up that when the target is red, that info is important. You will notice the target then illustrates a boat, but not red, when it changes course and moves away from his boat.
You will also note later in the video, three jet ski's are heading towards him but they are in pink, Garmin's way to say, these could be a problem but right not, not so. And you will see boats in front of him also heading out on the same track as he is on, they are in green. This is Garmin's way to say these boats are no problem. Obvious on a clear day, but think of this same video in the fog.

For me in "my situation," this option to warn of targets (up to 10) on a possible collision course is far more useful than seeing for a hundred miles (okay I exaggerate to make a point). I like Garmin, they assume I'm an idiot (a safe assumption) and make things easy for me.

For many, boating in areas that are more confined, or with a short hop of very open water, but the great majority of your location only ten miles or less on either side, you really don't need anything discriminating very distant targets. And so what if your radar doesn't discriminate between three kayakers and one, as long as you see the target. Or you can take the view of some BC Ferry Officers, they understand ocean kayakers as speed bumps. And by the way, the new broadband radar can pick up targets better near and further away than the older radar technology.

When I was on Canadian destroyers, back when Jesus was in diapers, the radar technology was definitely not user friendly, no chart over lay, the unit installed a number of feet from the helm requiring its own special person who peered down this long tube who's purpose was to block out light. My Garmin 18 Fantom is light years ahead of that puppy. In the old days, two radars - one to see far, one to see close. Now with broadband both near and far can happen simultaneously on one radar.

But if your boat is 25 feet and you want a 6 foot open array, I say go for it, it won't be any dummer than a cigarette boat.

 

[roddy]

Agree with rsn48.
Had 18 inch SiTex on 28 footer moored in New Westminster, BC
Long trip up and down Fraser River with lots of commercial traffic.
In this confined waterway with fog even with radar it was white knuckle trip.
Freighters travel at steerage speeds 10 knots+.
Even with radar I kept well to side of channel, dodging tied up log booms and barges...
Recreational boats don't get enough hours to get confident, IMO.

 

[Beaverlake]

We have a new Raymarine Doppler digital integrated with a class B AIS transponder. Cruising in the PacNW this provides us with a great tool in our often restricted visibility. As was noted elsewhere, for us the critical distances are ⅛ to 3+ miles. The logic includes the red/green color coding and when the Doppler feature is engaged I get great info. I have found that I’d rather do split screen vs chart overlay because in overlay mode there is just too much screen clutter. For me that was a change of opinion. Mind you I do use the overlay from time to time but in open water with fog I prefer the split. Plus I can chose to display AIS targets on the radar which helps.

 

[magna 6882]

I should clarify my thoughts. I am a person who does everything they can for safety. When i bought my last car i got all the accident avoidance options and i was criticized by some that i should buy a car for the fun of driving and not let the car do it for me.
I have a friend who does a lot of fishing in the sound and he has had fog roll in and has been a scary situation. He just idles along but has no idea someone is going to hit him.
That is my concern but i may learn more as time goes on. I ask the question because the the boat manufacture ask which one i want installed.

 

[Greatlaker221]

The practical difference. So the owner of a turtled trimaran hired me to find and salvage his sailboat 17 miles offshore. It had drifted after his rescue. I have many years of radar experience. That night I had a new 24” radome. I looked for hours with no luck. Later at night, I saw the lights of the Lake Express crossing Lake Michigan. I asked him if he could give me a fix. His huge array spotted the hull which was just 3’ above the surface. He gave me the coordinates 5 miles away and a bearing from my boat to the casualty. Impressive. I did not see it until I was 1/4 mi away. That was one of the very few times I needed more than a 24” radome. Unless you have a huge boat and plan to cruise extensively, a radome should be just fine. The latest generation units are impressive.