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Old 06-16-2014, 06:16 PM   #1
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Open Array vs Dome?

We'll soon be replacing the antique Furuno 1721 radar on our DF44 with a new Garmin unit. For those of you who've had both, how would you rate open array vs dome? What can you see with open array that you could not with a dome? Are OA worth twice the price (or more)? Are the newer domes better than the older OAs? Just gearing up to yet another major purchase.

Thanks.
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Old 06-16-2014, 06:48 PM   #2
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Just an over view:

Where are you going to use it? Open water cruising, lots of fog, crowded areas? Fishing? A long range open array is great for tracking storms, finding birds for fishing, defining targets over a wide area. Those ships and T-storms moving at 25 knots come on you quick.

If you are a casual coastal cruiser, the new "High Definition" and "Broadband" radars are super for nearby small objects like crab pots, dinghys, small buoys.
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Old 06-16-2014, 07:22 PM   #3
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What George said. It really depends on the type of cruising you will be doing as to whether you could justify going with an open array unit or not.

The new radars have very, very good pictures even when using a closed array dome.
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Old 06-16-2014, 07:41 PM   #4
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The biggest advantage to open array is target definition at longer distances.

There are technical parameters that deal with this...beamwidth and studying the specifications can be useful but generalizations work if you really don't want to dig too deep.

The rest is gross generalizations.

The broadband radars seem to shine in VERY close quarters as there is no or a very tiny "blank spot" on the middle...there's conflicting info on just how much better they are once you get out to an 1/16 of a mile or so...I had a hard time deciding which tech to go for.

Most trawlers travel slow enough that for close quarters work...a fdome is fine because by the time you get to where the OA was doing better...the smaller domes will tell you the same.

Power is a good thing (broadband excluded) to...power helps especially when dealing with environmental conditions such as rain and the ability to see into heavy stuff and filter out the rain itself.

For the typical trawler style boat here in the 40 something range...a 4kW unit is probably all you need.

The real trick is learning what any of them are telling you...so most any "newer" radar will be more than enough unless you are a 200+ day cruiser that travels day and night in any weather....the HD radars do have more bells and whistles but again the jury is out in my world if they are truly a step above non-HD radar.
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Old 06-16-2014, 08:53 PM   #5
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Quote:
The biggest advantage to open array is target definition at longer distances..
Yes, but how much range do you need? Some of the newer generation dome radars say they're good to ~30 miles under normal conditions. Furuno's radar calculator, for a unit 20' off the water, with a target 50' off the water will have an effective visibility range of 14 miles. Their words not mine.

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Old 06-16-2014, 09:03 PM   #6
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Yes, but how much range do you need? Some of the newer generation dome radars say they're good to ~30 miles under normal conditions. Furuno's radar calculator, for a unit 20' off the water, with a target 50' off the water will have an effective visibility range of 14 miles. Their words not mine.

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hey ...I'm with ya....

I got a little dome and I've been behind some of the most sophisticated radars made through the 90's.

I LIKE a radar to tell me the intensity of thunderheads at max range say 64NM or tell me yes there are some big boys out there in the fog speeding towards me...

But...I NEED a radar to confirm I'm in the middle of a choppy inlet in low vis at night say...picking out little, hard to detect buoys at 1/4 or 1/2 mile to me is the most important feature I desire...but that's me, my experience and cruising style that sets that NEED...it's also the most desired trait when I run the assistance towboat.

I went with a 4kW Raymarine dome...good price for a good radar.
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Old 06-16-2014, 11:31 PM   #7
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All good thoughts, thanks. To answer George and others, initially, we'll be on the Chesapeake, but we're talking about everything from the Great Lakes to the VIs to Nova Scotia. We've boated in all those areas in the past and want to have the ability to pick up nav aids, thunderheads and commercial vessels at some distance.

Wonder if there's anywhere you can actually see the new stuff and compare them side by side?
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Old 06-16-2014, 11:33 PM   #8
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We went thru this when we upgraded Pau Hana- we went with the 4kw HD Raymarine open array radar.

While the power output is the same, I prefer the target separation that the open array gives over the dome.
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Old 06-17-2014, 12:00 AM   #9
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if it's shipping that is a big deal, go a bit less than optimal on the radar, and add AIS to the mix.. much further target acquisition of ships and all the data at a glance. At the ranges I tend to use most (16-24 mile) I don't really see much difference in open vs. closed array.
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Old 06-17-2014, 12:10 AM   #10
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The big difference is that the open array is usually a larger or longer sender receiver and that will give better definition of targets all else equal. That said for most purposes a modern 24 inch closed in array is adequate. If you need to have better definition a 48 inch or greater unit is superior. and that is open. I presently have a modern 48 inch open array and I believe I can notice a significant improvement in definition from my recent modern 24 inch closed array.
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Old 06-17-2014, 12:13 AM   #11
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In my constrained waters, usually operate using one-mile range or less, and there is little use for more than six miles.
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Old 06-17-2014, 01:22 AM   #12
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The number 1 reason for oa, though few will admit, is that it looks really cool.
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Old 06-17-2014, 02:32 AM   #13
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The number 1 reason for oa, though few will admit, is that it looks really cool.
+1 ... especially on a bigger boat ...
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Old 06-17-2014, 03:40 AM   #14
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I agree with Hollywood that one strategy would be to go for a lower-cost/lower power radome and put the saved $$ to an AIS unit. Let me float another: I have a current-model Furuno 4kW radome and the limitations are more about my skills in interpreting the image than in the capabilities of the unit itself. If I were starting over on my electronics, I would put one of the new reduced-price FLIR (or re-badged RayMarine) thermal imaging cameras ahead of a radar...but that's because I rarely have to deal with fog but often want to leave or enter harbour in the dark.
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Old 06-17-2014, 05:44 AM   #15
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My little 12" Lowrance dome can see thunderstorms, but is near worthless were you really need it, close-in with fog. The main bang circle blots out everything inside a 1/10 mile radius!!!
IMHO, buy a 4 kw dome. Find someone with a unit like what you want to buy and check it out. You may find the unit works great but simple tasks like changing gain or rain clutter are menu driven and will drive you insane. I miss the days of a Gain knob.
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Old 06-17-2014, 07:50 AM   #16
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The number 1 reason for oa, though few will admit, is that it looks really cool.

+2 Especially when you turn the rotation speed to 48RPM.
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Old 06-17-2014, 05:18 PM   #17
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I agree with Hollywood that one strategy would be to go for a lower-cost/lower power radome and put the saved $$ to an AIS unit. Let me float another: I have a current-model Furuno 4kW radome and the limitations are more about my skills in interpreting the image than in the capabilities of the unit itself. If I were starting over on my electronics, I would put one of the new reduced-price FLIR (or re-badged RayMarine) thermal imaging cameras ahead of a radar...but that's because I rarely have to deal with fog but often want to leave or enter harbour in the dark.
Good idea. I have a night vision monocular I plan to try out in two weeks. It's not IR, but if it's anything like the one I used on a Bermuda trip several years ago, I'm going to love it.
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Old 06-17-2014, 05:24 PM   #18
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Originally Posted by hollywood8118 View Post
if it's shipping that is a big deal, go a bit less than optimal on the radar, and add AIS to the mix.. much further target acquisition of ships and all the data at a glance. At the ranges I tend to use most (16-24 mile) I don't really see much difference in open vs. closed array.
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AIS will definitely be part of this boat's electronics. We had a scare with a fast-moving freighter obscured by bright city lights in the background off the Jersey coast once. I know it would have showed up on radar--if we'd had it--but I like to be overly cautious now.

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The number 1 reason for oa, though few will admit, is that it looks really cool.
Too true!
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Old 06-17-2014, 05:49 PM   #19
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I miss the days of a Gain knob.
I still have an old late 80s vintage Ratheon 47 OA on my boat. It has lots of gain knobs! Will be going with a new Raymarine OA and chart plotter w/AIS....
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Old 06-17-2014, 05:55 PM   #20
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I have been using Class B AIS through my NMEA2000 network for the last 4 years. Every year I see more class B transponders it's catching on. The class A vessels can be seen at quite a distance. I like having the ability to immediately identify another AIS transponder users MMSI, bring up his vessels information as it relates to my vessel and place an MMSI call directly to negotiate a passing. Don't just get an AIS receiver you need to be seen and not just see others. AIS unlike Radar see's around corners. Both compliment each other I wouldn't do without my Garmin GMR18HD Radar, it has a gain knob but it's not a knob but an on screen slider very easy to use and it works fairly well close in. For real close in my FLIR works quite well but the unit was pretty expensive.
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