Radome size

Getting ready to install a new electronics package and have chosen Raymarine. I'm debating between the 18" v 24" HD radome. The size of the 18 dome (which is about 20") works a bit better for my new mounting spot and save about $700.

Both are 4kw so the difference is beam width (3.9 to 4.9) but I'm unsure what that means to coastal cruising in the PNW? What am I giving up with the 18"? Coming from a 1980's Furuno analog so that's my reference point.

Boat is a 42 GB sportfish if that matters.

Generally the dimension (18") refers to the antenna element inside not the dome itself. The simple answer to your question is that the wider the array, the better the seperation and detail of targets. In the smaller arrays, you will see targets if they're larger at a greater distance, and smaller ones only closer. As an approximate example, the 60' high interstate bridge will be seen at 10+ miles. The 25' center console might be seen at 5 miles. The smaller floating channel buoys can be seen at 1 mile. It has to do with how much energy you can pinpoint at a target. The wider the array the narrower it can pinpoint and illuminate a target for the same KWs of power.

The other difference is target seperation. With the 5KW 3' open array on my charter boat, I can see a 25' center console fishing next to the seabouy at 2 miles away. With the 18" antenna you won't see 2 separate targets till you're between them.

Nothing wrong with the 18" antenna if you understand it's limitations. With any radar, the only way you get good (comfortable) with it is to run it during the day and learn to interpret what it is and isn't showing you. Mine runs all the time that the boat is moving. As I get older, I see the smaller targets sooner on the radar than with my 20/20 corrected vision.

Ted

The wider the antenna the better the separation. We have a 24" antenna for our Furuno NavNet. A friend has an 18" antenna on his Furuno and the difference in target clarity and separation is significant. Given the things like rocks, reefs, navaids, small sport fishing boats, crab pot floats, etc. in these waters we would always opt for a wider antenna. To us and based on the difference we've seen an 18" antenna is too limiting in this respect. We'd have gone wider than 24" if the antenna would have fit on our mount.

While just about everything can always be "better"....often on recreational boats, adequate is good enough.

For me, going at Trawler speeds and only needing radar a handful of times a year....superior target separation at longer distances isn't really needed. Once you get close, even the smaller radomes give separation.

Being able to correlate targets with charted objects is important. While overlay can be great...it too isn't all that necessary if you can set your electronics up to give you a reasonably clear idea of what is out there.

Just for comparison, I have a 12" Lowrance (Koden) dome radar on my CC in NJ. Without a doubt it is the worst performing radar I've ever used or owned. Target separation is poor at best in a harbor. Several boats in an anchorage look like a wall. A rock jetty inlet open to the ocean looks like a dead end canal.
If you usually have fog or rain in your area, go big as you can. You won't regret it.

Fwiw that 1 degree beam width equates to a little more than 5 feet at 100 yards or 50 feet at a thousand given the same pulse length etc..


Via iPhone.

In all fairness...radars changed quite a bit with the Raymarine Pathfinder series back 15 years ago.

None of the other smaller, lower power radars came close to their performance because of using different pulses for different ranges.

I would venture to say that all manufactures have caught up now.

I would go with a 24 in, 4 kw dome....digital.....high Def seemed a bit over the top with little actual performance improvement that I could see. Only the smallest of boats really can't handle the 24 in....but if space is an absolute issue....as long as you are an occasional cruiser, 18 in might be adequate in today's newer radar (especially the broadband if you feel that type is for you).

psneeld said:

In all fairness...radars changed quite a bit with the Raymarine Pathfinder series back 15 years ago.

None of the other smaller, lower power radars came close to their performance because of using different pulses for different ranges.

I would venture to say that all manufactures have caught up now.

I would go with a 24 in, 4 kw dome....digital.....high Def seemed a bit over the top with little actual performance improvement that I could see. Only the smallest of boats really can't handle the 24 in....but if space is an absolute issue....as long as you are an occasional cruiser, 18 in might be adequate in today's newer radar (especially the broadband if you feel that type is for you).

Click to expand...

I agree. I just installed a 24" HD Dome and love it! It will not disappoint. The one thing I did find out was I am unable to overlay my radar onto the MFD without an electronic compass. I was told the reason was liability. The GPS would keep up with the "go fast" boats and then would hit stuff as the operator was not paying attention to the radar. I just run a split screen and can toggle back and forth with a full screen if needed.

I vote the 24" HD Color.

Personally I am more concerned with what is close to me not 10 miles away. I seldom run my radar at greater than the 2 mile range setting, which is adequate for trawler speeds. An 18" dome is fine for those close ranges. If my boat was a go-fast, I would want longer range capability, which would likely mean a larger antenna, although my 18" radome (Lowrance Broadband) has a 2.9 degree beam width, which is better than the 24" Raymarine you are looking at, so maybe I wouldn't need a larger antenna.

We generally run our radar at ranges between 0.125 and 3 miles. However even at these short ranges from what we've seen the 24' antenna is superior to an 18" antenna. When it's foggy we boat in the fog and having good clarity and target separation is essential.

Add AIS with your radar and you have a great tool in your toolbox......

Thanks for all of your feedback. 24" ordered.

Lots of close-by targets here of small boats anchored in Richardson Bay, here using a small radome:

I'm an open array fan vice the dome. Better lobe separation and target definition. We were coming back from Tacoma Sunday evening and the radar (Raymarine 4kW HD open array) was picking up small fishing boats, buoys, etc., at 3 miles.

That being said, the 24" dome IMO is a much better choice than the 18".

In areas with dynamic weather conditions, a longer distance radar capability is an excellent tool for tracking storms. They can move very quickly and be on the unsuspecting mariner before course change or preparations can be made. Also, if you are in a sea lane with large ships, which clip along at 20+ knot speeds, again they can be on you right quick; Not to mention sportfishermen, high performance center consoles, Cigarette style boats et al....you may not be a go-fast but they are!.

The only time we dial down our range is in confined passages like the ICW or Delta sloughs in the fog. For us, radar was the most important piece of electronics along with the depth finders. Followed by the VHF, with the plotter way down in priority. And we don't even like cruising at night.

How much range do you need to see what's in front of you? If you want to track storm clouds or a flock of birds OK maybe, but ships and other boats? If your radar is mounted 20' off the water and you are seeing one of the new Triple-E container ships (240' tall), you only need a 24 mile radar. Beyond that, he's out of your effective range according to Furuno.

Radar Horizon Calculator

If you think of how few even use their boats away from the dock and then think how many that do travel in conditions where radar is necessary and can use it to 1/2 it's capability......most can get by with the smaller sets that are still decent. Can't disuss them all but many of the newer 18 to 24 dome 4 kw are more than "adequate".

Sure bigger, more power and open array is the ticket.....but overkill for many.

Larry M said:

How much range do you need to see what's in front of you? If you want to track storm clouds or flocks of birds OK maybe, but ships and other boats? If your radar is mounted 20' off the water and you are seeing one of the new Triple-E container ships (240' tall), you only need a 24 mile radar. Beyond that, he's out of your effective range according to Furuno.

Radar Horizon Calculator

Click to expand...

You are assuming the performance of that 24 mile radar is the same at 24 miles as it is, say at 4. And /or that the 24 mile range unit has the same definition and usability as a larger, higher power unit at that distance or distances even less than that. Having been on a few boats with both a radome and an open array, or comparing my radar to those nearby at anchor with higher or lower power/size, I can tell you, in my strong opinion, that is certainly not the case.

I will say, that the new "broadband" or "high definition" domes are really excellent, especially at close range. If I was only going to be boating in protected waters, I wouldn't mind at all having one as my only unit. In fact that was on my list, to add one in addition to our open array, but that last needed number on the lottery ticket never came up and we survived without it.

Since our boating in recent years has been in areas with a lot of squalls and thunderstorms, yes, we really enjoyed having the long range capability and used it a lot.

As with all systems....it depends....

Where do you find yourself 90% of the time?

In the last 8000 or so miles on the ICW, an annual trip to Florida and back....the 4 to 5 times I needed to pick out bad squall lines involving possible tornado action would have been hampered by tall trees lining the ICW.

If the weather is forecast to be really bad, such as I described, I probably won't be venturing into open water..for very long.

So while I agree a more powerful, long range high Def radar is great....just how often does one really expect to use it? On the ICW, money is better spent on a Hotspot for Internet weather as you can see it when your radar wont.

Same with open array or dome. When I get within a 1/2 mile of a target and it finally separates into 2 targets.....at 6.5 knots....it takes almost 5 minutes to get there and in 1/4 mile or less fog, I stil, have plenty of time to check if they both are charted targets or not.

If I were going to run 10 knots plus in 1/4 mile visibility (not smart as a recreational guy)....then all that definition becomes a bigger deal.

Got the money, the room and the cash?...go for it. Travel a lot at night or crappy weather?...go for it

The average guy on TF? Spend your money wisely.

Larry M said:

How much range do you need to see what's in front of you?

Click to expand...

That's a real good point for potential radar purchasers to keep in mind. The requirements for a blue water cruiser are going to be different from the requirements of a coastal cruiser. And in the coastal cruiser category the requirements are going to be different for someone cruising in the maze of islands and channels that make up the PNW, BC, and SE Alaska coasts and (I imagine, having never done it) someone cruising long waterways like the ICW.

Here in the PNW, the straight-line range to an obstacle like an island or the mainland is rarely more than three to five miles other than on the larger bodies of water like the Strait of Georgia, Queen Charlotte Strait, and so on.

Our Furuno NavNet VX2 with a 24" antenna has a theoretical range of 36 miles (IIRC). But what we're really interested in is its sensitivity, return clarity and target separation from 0.125 to 3 miles.

The longest range I can ever recall setting the display to is six miles and that was more to see what it looked like than to actually use it. Sun or fog, we are always running at three miles or less. In the very narrow passes we go though, sometimes in dense fog, we'll be at 0.125, 0.250 or 0.50 so we can see crab trap floats, little sportfish boats, etc.

We would have purchased our NavNet with a 36" antenna if it would have fit on the mount. Not because we care about seeing any farther but for the increased target separation and clarity. But we've found our 24" antenna does fine for us.

Our antenna is also mounted fairly low. Not a problem for us since we don't need to see long distances, and it's an advantage in seeing small things on the water right up to the boat. If we were open water boaters, however or were boating long, straigh-ish waterways where seeing what was coming at us or up behind us while it was still some distance away, a low mount like our would not be beneficial at all.

So, like almost everything else to do with boating, there is no one-size-fits-all solution when it comes to what radar antenna and radar power is best for each boat.

I think we are all strenuously agreeing with each other. Right tool for the right circumstances.

Though I would note, have been the length of the ICW a few times, at least 80%, more like 90, is not confined enough to obliviate picking up weather. I subscribe to and regularly use the good weather radar sites too, had locations bookmarked along the entire eastern seaboard all the way back to the Blackberry days, but they do not place my boat at the middle of the screen, nor do they track the relative bearings and collision point of my boat and the weather. And yes, we have anchored, tucked in, hoved to, slowed down, sped up all a few times as a result. To be sure, we were also out in blue water perhaps more frequently than others, but certainly did our time inside.

I ordered the 24" HD and a Ray A128 MFD. Before ordering I almost posted another question about digital v HD radome. But I decided to just get it over with and ordered the HD.

Looking at Markpierce's picture - which I'm guessing is "digital" (?) and not "HD" - I'm wondering if I over-killed for my situation with my decision. That photo looks far beyond what I'm used to and certainly safe for PNW navigation.

We aren't looking for squalls, birds or, as mentioned, ever looking more than 3 or 4 miles - usually more interested in .125 miles in pea soup.

Anyway, I'm committed. But maybe someone else can benefit if anyone advice. There isn't much I have found on the www.

If by "digital" you mean the typical radar withl LCD-type screen that's been around forever, we've certainly found it to be more than adequate for our boating in this area.

Not saying that an HD radar isn't any better but once we upgraded way back when from our dying hood-required CRT Raytheon 2600 to the Furuno NavNet VX2, we have never found ourselves wishing for a better radar, either in function or display. And we do a fair amount of boating in the fog, particularly in the fall and winter.

Bradenvlp said:

...

Looking at Markpierce's picture - which I'm guessing is "digital" (?) and not "HD" - I'm wondering if I over-killed for my situation with my decision. That photo looks far beyond what I'm used to and certainly safe for PNW navigation.
...

Click to expand...

Don't know, but whatever, it's merely a C70 Raymarine setup with an 18-inch radome. ... I rarely expand range beyond a mile or two because of the restricted waters here in the SF Bay/Delta.

Bradenvlp said:

I ordered the 24" HD and a Ray A128 MFD. Before ordering I almost posted another question about digital v HD radome. But I decided to just get it over with and ordered the HD.

Looking at Markpierce's picture - which I'm guessing is "digital" (?) and not "HD" - I'm wondering if I over-killed for my situation with my decision. That photo looks far beyond what I'm used to and certainly safe for PNW navigation.

We aren't looking for squalls, birds or, as mentioned, ever looking more than 3 or 4 miles - usually more interested in .125 miles in pea soup.

Anyway, I'm committed. But maybe someone else can benefit if anyone advice. There isn't much I have found on the www.

Click to expand...

You can't have too good a radar. If you cruise enough, you will come to appreciate that. If you set it at .125 while the boat is underway, you are going to hit something, or something will hit you. There are some very good discussions of modern radar options on The Hull Truth's Marine Electronics forum, if you scan back through the archives.

Get a copy of The Radar Book by Monahan, the best guide I've seen for learning how to use one and all it can do for you. And once you have it installed, use it all the time; it's on the clear days when you learn what it is picking up (or not), and a safer time to play with all the functions like MARPA.

Thanks. I'm rather comfortable reading a radar and have been doing it for many years. Im not sure where I implied that I'm not. I'm less comfortable with the differences in the new innovations. There seem to be digital models with each manufacturer which seem to be taking an analog signal and converting to digital. There is also HD (4g, etc depending on manufacturer) which is a pure digital signal. It gives you color. I'm not sure that is better or just cool.

In our waters it is not unusual to find yourself running at 2 or 3 knots because you have trouble seeing your pulpit in the fog. Or to be trying to get into the marina without being able to see the breakwater on either side. Close range becomes very, very important.

We almost never have a need to look beyond 3 -5 miles as it doesn't matter to me what is on the other side of the Island.

Bradenvlp said:

Thanks. I'm rather comfortable reading a radar and have been doing it for many years. Im not sure where I implied that I'm not. I'm less comfortable with the differences in the new innovations. There seem to be digital models with each manufacturer which seem to be taking an analog signal and converting to digital. There is also HD (4g, etc depending on manufacturer) which is a pure digital signal. It gives you color. I'm not sure that is better or just cool.

In our waters it is not unusual to find yourself running at 2 or 3 knots because you have trouble seeing your pulpit in the fog. Or to be trying to get into the marina without being able to see the breakwater on either side. Close range becomes very, very important.

We almost never have a need to look beyond 3 -5 miles as it doesn't matter to me what is on the other side of the Island.

Click to expand...

I tend to agree....if you only have one radar on board...it better be useable down to several hundred yards....that's where absolute target discrimination matters the most. In fog on the ICW, I often run with it at 0.25 miles....and at times go lower.

Next most important to me is picking buoys out of a choppy inlet....while I tend to really trust GPS and it's backup GPS....I really like to be able to verify my nav with seeing the buoys on radar.

Every other feature of the radar is just gravy.

Any comments on the new Simrad Halo solid-state open array radar? Read about it on Panbo this morning. The reviewer seems to be impressed but I am not so sure what is different and have a suspicion the software issues reported by Twisted will show up in this radar also.

Donsan said:

Any comments on the new Simrad Halo solid-state open array radar? Read about it on Panbo this morning. The reviewer seems to be impressed but I am not so sure what is different and have a suspicion the software issues reported by Twisted will show up in this radar also.

Click to expand...

Over hyped. They'll probably release with half the code written and the other half will take a year. "Everything on Panbo is the next biggest thing"--Peter H. Very accurate.

.125 , 750 feet, is just cutting it too close in my opinion. You may be going 2 knots (200 feet a minute), but the guy that is going to hit you will be going much faster, often, insanely fast. Even if he's only going 8 knots, that makes your closing speed 45 seconds. The craziness that one sees on the screen in dead low visibility is, well, just crazy. In a very narrow passage, such as some parts of the ICW or the CA Delta sloughs, we will typically have it at .25 and someone on the bow listening. In practice, I'm working the range up and down depending on conditions and how much of the channel is radar visible (usually a lot of it in low country like the subject areas).

The Radar Book is excellent regardless of your experience. And for you PNW folks, pretty fun since he uses that area as his template. And with a new piece of machinery especially, but in general as a best practice, having the radar on all the time when underway and manipulating it is very helpful.