Open Array vs Dome?

Hmmm... I'd have guessed gain is set too high in those pics... on both units...

I'll maybe fire up our unit at the dock and see what that looks like for comparison. I know on the water when we're trolling, we can usually see our planer boards on the radar... and these are (relatively) tiny lo-profile things about 80' off our stern quarters...

-Chris

Billylll said:

Yes it does exceptionally well in heavy fog especially close in. Also the FLIR has nothing to do with night vision, it has everything to do with detecting differences in the temperature of objects within it's field of view.
Bill

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My FLIR (I don't remember the model, but I purchased in 5 years ago for a little over $10K, so it isn't their cheapie, but it isn't the $50K unit either) doesn't do well in heavy fog, and that doesn't surprise me since the water in the fog easily absorbs thermal energy. Absent fog, it is amazing -- you can see someone peeing 1000 feet away; you can tell how full someone's beer can is (even if there is no condensation on the outside).

All infrared is pretty severely affected by moisture and rendered nearly useless quickly in tropical rain. Blackbody radiation is really negatively affected by warm, wet moisture (fog). I used to operate a FLIR on P-3's in the Navy and when we'd operate down south the tropical rains put me out of business pretty quickly. Radar (used in conjunction with FLIR and LLTV) is the sweetest setup.

Mine has done well in heavy fog it's the distance gets more limited. Who's travelling fast in the fog anyway? Not me. It has great value in heavy fog when used in conjunction with Radar and AIS.
Mine is the 10k unit not the 50k, I have used the 50k version but not with boating.
Now NJ doesn't get tropical fog so I can agree with that statement.
Bill

MYTraveler said:

My FLIR (I don't remember the model, but I purchased in 5 years ago for a little over $10K, so it isn't their cheapie, but it isn't the $50K unit either) doesn't do well in heavy fog, and that doesn't surprise me since the water in the fog easily absorbs thermal energy. Absent fog, it is amazing -- you can see someone peeing 1000 feet away; you can tell how full someone's beer can is (even if there is no condensation on the outside).

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The first airborne FLIR ever mounted on a helo (at least that's what we were told) was a prototype by Northrop back around 1982. It was on a USCG helo in Miami, Fl.

It was good enough to see the rough outlines of the rotting banana stalks that were pressed against the inside of the hull of a banana ship...can't remember if Dole or Chaquita.......

You could see lot's a other things...should'a had an "R" or "X" rating for younger co-pilots...

angus99 said:

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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Radome antennae cost less, consume less power and have less windage. These are all attributes sailors find useful. Open arrays are the opposite end of the spectrum. New radomes vs. old open arrays might possibly get close, but they still are constrained by the physics of all radars. Power, pulse width, beam angle etc.. all being equal you could go either way, the problem is I don't think anyone produces a radome that is equal. To compare apples to apples, take the units price and divide it by the power to beam angle ratio (the higher this number the better). Should help you see the value per dollar of comparable units.



Via iPhone.

Although I have never had both dome and OA installed at the same time on the same boat, so I can't give a direct comparison, but for what its worth, in my experience (which does not apply to broadband):
1. First, inside every dome IS an open array, so from that perspective the only difference is how the array is protected -- either it is completely within a dome, or it is in a housing covering only the array, which must therefore rotate. To house a 4' array requires a very large dome -- at that point OA make more sense; big arrays just don't fit in domes. So if you are comparing two equally sized arrays, everything else being equal, the dome will perform exactly the same as the OA. But, two benefits come from increasing the size of the array -- better target separation and more power. In my opinion, target separation is highly overrated. If I see an echo return on my radar, I avoid it whether it is one boat or two. Power, on the other hand, will return weaker targets more strongly and from a greater distance (at least so long as they don't fall below the horizon).

cafesport said:

Radome antennae cost less, consume less power and have less windage. These are all attributes sailors find useful. Open arrays are the opposite end of the spectrum. New radomes vs. old open arrays might possibly get close, but they still are constrained by the physics of all radars. Power, pulse width, beam angle etc.. all being equal you could go either way, the problem is I don't think anyone produces a radome that is equal. To compare apples to apples, take the units price and divide it by the power to beam angle ratio (the higher this number the better). Should help you see the value per dollar of comparable units.


Via iPhone.

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Cafesport, how do you divide a number BY a ratio? I understand how to divide into a ratio, but not by one.

Thanks again.

A ratio is also a number. Take a 6kw unit with a 1.8 horizontal beam angle for $4000. (Simrad tx06s on defender's website). 6kw/1.8degrees=3.3kw /degree. $4000/3.3kw/degree=1212$/kW/degree. The 10kw unit is 5400 but it has a narrower beam width 1.2 and equates to 650$/kW/degree. Almost twice the value


Via iPhone.

Can 4G dome (broadband) be judged like a 2kw dome vs 4kw open array? Aren't they different technologies?

cafesport said:

A ratio is also a number. Take a 6kw unit with a 1.8 horizontal beam angle for $4000. (Simrad tx06s on defender's website). 6kw/1.8degrees=3.3kw /degree. $4000/3.3kw/degree=1212$/kW/degree. The 10kw unit is 5400 but it has a narrower beam width 1.2 and equates to 650$/kW/degree. Almost twice the value


Via iPhone.

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But in this case, narrower is better! Using your math, if the cost of two units were identical, but one had twice the horizontal beam width of the other, it would seem to indicate that the wider beam was twice the value. But, clearly, the narrower beam, for the same price, would be the better value.

and there's a lot more to RADAR than just beam width and power.....it may be one marker but just one of many.

Larry M said:

Can 4G dome (broadband) be judged like a 2kw dome vs 4kw open array? Aren't they different technologies?

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I believe they are very different technologies however the 4G units are supposed to be spectacular close in.
Bill

cafesport said:

A ratio is also a number. Take a 6kw unit with a 1.8 horizontal beam angle for $4000. (Simrad tx06s on defender's website). 6kw/1.8degrees=3.3kw /degree. $4000/3.3kw/degree=1212$/kW/degree. The 10kw unit is 5400 but it has a narrower beam width 1.2 and equates to 650$/kW/degree. Almost twice the value

Via iPhone.

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Got it, thanks. Interesting way to look at it. I still need to see some real-world screen shots to see if 0.6 degrees of horizontal beam angle is worth another one and a half boat units.

caltexflanc said:

That doesn't look like it is tuned correctly. I know the conventional wisdom is the Furuno is "best", but my Furuno 6kw open was much much much sharper than that at close range, say in a crowded anchorage, harbor or marina setting. It's not that much better. I'll have to see if I have a pic somewhere in the archives.

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Here on screen shots from my Furunos, a 6kw (top) and a 25kw. Both are in auto tune:

This is a Si tex 4kw 5' array I easily spot channel markers at 3/4+ miles which is what I wanted radar for. I never had radar before this so don't have anything to compare to.

More important than what unit to buy is learning to use you what you have. I purchased "The Radar Book: Effective Navigation and Collision Avoidance" by Kevin Monahan and I realized there's a lot more to using radar than I had previously thought. Reading the book together with the operator's manual and with the unit itself has been particularly revealing. He points out that many operators haven't properly tuned their unit in the first place.


Jim
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JDCAVE said:

He points out that many operators haven't properly tuned their unit in the first place.


Jim
Sent from my iPad using Trawler Forum

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Not only are many sets not properly tuned, the gain is not properly adjusted for the conditions or circumstances the unit is being use for.

I find myself very often having to explain to crew that while a picture with little or no scatter on it may look pretty, you are just cutting out your ability to see weak targets by backing the gain down to much.

When I'm running offshore at night I want to see the returns from weak targets like small sailboats and fishing pangas at as great a distance as possible. And the only way that will happen is if you crank up the gain and start getting scatter returns from say wave tops. I don't care if my picture has a lot of clutter in it as long as I can pick up the weak targets as far out as possible. I can always adjust the gain down for a cleaner picture as I get closer to that target and it gets stronger.

Right on Jim and Bill. That's one of the reasons it is so important to use and play around with your radar on nice days. Unless going on a very short hop, I try to have it on all the time; besides learning and increasing familiarity, it gives you a more complete survey of what is around you. Studying the owner's manual and reading the Monahan book Jim mentioned. That way when it is really needed, you know what you are looking at and how to adjust it accordingly.

Exactly, Bill. Monahan points out that people should not turn the anti clutter adjustment too high as it might gate out weak targets. Also, I believe the Collision Avoidance Regulations state if radar is installed on the vessel, it must be on at all times when the vessel is in transit.


Jim
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Being on the river I use mine on 3/4 to 1 mile most of the time. I use the auto tune function on mine and the screen is fairly clear except for targets and returns from my wake. Took me awhile to figure out what I was seeing until I slowed down and the little tails disappeared. After moving a boat thru the Great Lakes I can see the value of setting radar on 3 to 6 mile range on large open water and even farther if looking for thunderstorms.

JDCAVE said:

Exactly, Bill. Monahan points out that people should not turn the anti clutter adjustment too high as it might gate out weak targets. Also, I believe the Collision Avoidance Regulations state if radar is installed on the vessel, it must be on at all times when the vessel is in transit.
Jim
Sent from my iPad using Trawler Forum

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Here is what the Rules have to say. They don't make a hard requirement to use it, depending on conditions, and it must be used "properly" when it is. My attitude is, why not have it on all the time?

(a) Every vessel shall use all available means appropriate to the prevailing circumstances and conditions to determine if risk of collision exists. If there is any doubt such risk shall be deemed to exist.
(b) Proper use shall be made of radar equipment if fitted and operational, including long-range scanning to obtain early warning of risk of collision and radar plotting or equivalent systematic observation of detected objects.
(c) Assumptions shall not be made on the basis of scanty information, especially scanty radar information.

Some to storms on the radar in the Abacos.

Brilliant, guys. Now it's off to Amazon for another good book!

JDCAVE said:

Exactly, Bill. Monahan points out that people should not turn the anti clutter adjustment too high as it might gate out weak targets. Also, I believe the Collision Avoidance Regulations state if radar is installed on the vessel, it must be on at all times when the vessel is in transit.


Jim
Sent from my iPad using Trawler Forum

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Is that a Canadian "special" reg as some are????

Not trying to be funny but based on my reading and personal interpretation is paragraph a. trumps b. by the use of the words "prevailing circumstances and conditions ". I have read expert testimony in cases where the thought was if RADAR and other devices were ALWAYS needed...they wouldn't need paragraph a. stating "prevailing circumstances and conditions ". .

Rule 7 - Risk of Collision

(a) Every vessel shall use all available means appropriate to the prevailing circumstances and conditions to determine if risk of collision exists. If there is any doubt such risk shall be deemed to exist.

(b) Proper use shall be made of radar equipment if fitted and operational, including long-range scanning to obtain early warning of risk of collision and radar plotting or equivalent systematic observation of detected objects.

N4712 said:

Some to storms on the radar in the Abacos.View attachment 30752

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For the benefit of people like me who haven't had the opportunity in the areas we boat to use radar for storm cell location (I use a weather app with a radar) what range do you use? Also how can you determine the return is a storm if your in a unfamiliar area and not a land mass, is there something distinctive about the return? On the river when a storm is coming most of us head to our slips if available, I got caught in a thunderstorm on a holiday weekend a few years ago and my bimini top had some of the stitching tore out.

That picture is a good example of what I was talking about. The gain on that unit appears to be turned down, is set to auto or perhaps has the anti clutter feature turned on so there is no clutter at all showing. Which is fine for picking up thunderstorms, land masses and large vessels. But would not be very good for picking up small vessels or vessels with a weak radar return.

River Cruiser said:

For the benefit of people like me who haven't had the opportunity in the areas we boat to use radar for storm cell location (I use a weather app with a radar) what range do you use? usually max range till the big cells are closing in Also how can you determine the return is a storm if your in a unfamiliar area and not a land mass, is there something distinctive about the return? yes...very distinctive..they look ghost like and often move pretty quickly and they undulate like a blob. On the river when a storm is coming most of us head to our slips if available, I got caught in a thunderstorm on a holiday weekend a few years ago and my bimini top had some of the stitching tore out.

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Practice at the dock if you can..all in all spotting them and getting an idea of how heavy the rail is and their direction is all pretty easy. Blending that current info with what you should have picked off the internet earlier is real important too...but that takes some training in weather basis...try NOAA and other sites for some online tutoring...it's worth it...

River Cruiser said:

For the benefit of people like me who haven't had the opportunity in the areas we boat to use radar for storm cell location (I use a weather app with a radar) what range do you use? Also how can you determine the return is a storm if your in a unfamiliar area and not a land mass, is there something distinctive about the return? On the river when a storm is coming most of us head to our slips if available, I got caught in a thunderstorm on a holiday weekend a few years ago and my bimini top had some of the stitching tore out.

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Honestly I'm new to radar my self, but storm cells will usually show up as a big blob like in the picture. At least that's what I've ran into so far. Are general range on the radar is 3-6 NM.

Thank you both for the replies, I think I have a better understanding now what a storm return would look like on the screen.