Question: What is your preference regarding the best place to mount a radar antenna? As far as we can tell from the pictures of Morgan’s Cloud you have mounted yours on a pole aft. Our previous experience with radars tells us that the antenna should be as high and free as possible. Wouldn’t a radar antenna mounted on the mast just above the first spreaders give better range and a more detailed radar picture than if it were mounted lower? It also appears from the pictures that your antenna isn’t mounted in a way that makes it able to tilt so that it can compensate for heel of the boat when sailing.
Answer: First off, we should say that we view radar as the most important piece of electronic equipment on Morgan’s Cloud—yes, more important than GPS, since we can find our way with a compass and sextant but we can’t see unlit objects at night or through fog—so we have given a lot of thought to the position and installation of our radar scanner.
We prefer a pole mounted aft for the scanner over mast mounting for the following reasons:
- The scanner is much less vulnerable to damage from an errant halyard or sail.
- We do not agree that a higher position for the scanner is a significant benefit. Small targets, like buoys, don’t show much over a mile regardless of scanner height and large targets, like ships, show at 10 miles—plenty of room to plot and take avoiding action—with our current scanner height. In fact I think that putting the scanner substantially higher than ours can be a disadvantage since it will be subjected to more motion in a seaway.
- A scanner on the mast is more difficult to service than one on a pole and heaven help you if the cable needs replacing.
- Mast mounted radars are very vulnerable to damage when the mast is un-stepped.
- We don’t like the added weight aloft. Sure it’s not that much, but with the lever arm, every pound counts.
About the only advantage I can think of for a mast mount would be a theoretically less impeded view forward. However, in the real world we have never found that there was any appreciable radar shadow cast by the mast and rigging.
Our radar scanner can be inclined to compensate for heel using a clever system based on a speedboat hydraulic trim tab pump and actuator. We got ours from Edson, although a reasonably handy owner could duplicate our system, by buying the gear directly, for less than Edson charges.
We would not be without this tilt feature since it is just plain dangerous to sail around with a huge radar blind spot on either side of the boat when heeled. This was graphically brought home to me the second year I owned Morgan’s Cloud (before we installed our incline system) when we were nearly run down in thick fog by a trawler that we only saw at 100 yards and that visually, not on radar, approaching from our port beam. Yes, I know we had the right of way, but with huge steel trawlers traveling at 10 knots that is scant comfort!
Incidentally, we far prefer our manually controlled (using a switch in the cockpit) inclining system to gimbled backstay systems like the Questus. Our thinking is that no matter how well damped the latter is, there are just too many bend cycles being put on the cable. Also, back stays are prone to vibration, surely not a good thing for sensitive electronics.
Huh…once again a post referenced to another post emerges from the past to get me musing. We have two steel supported 25 square inch “tabs” welded to the stern, and while I just took it as a given that we would mast-mount the radar, a tilt-able radome on a beefy pole makes a lot of sense. The other steel tab would take a wind generator on a pole. Weight on the stern isn’t a huge issue and it’s a lot less than the now-departed davits produced. In addition, the pipe rail situation is such that robust bracing of the pole is easy to accomplish.
May I ask if your radar mounts “antenna arms” are custom or off-the-shelf? Seems like a good place to put a dedicated (i.e. tuned) AIS antenna and a backup VHF whip.
Hi Marc,
Yes, on a pole is way better than on the mast in my opinion. The arms are from Edson.
OK, John, you’ve made a convert. Out of curiosity, how do you a) bring conduit through the deck and b) insulate the pole (I’ve considered a bevelled out hockey puck and 4200!) from the metal deck (dissimilar metals?)
Hi Mark,
Our radar cable comed down inside the tube of the stand. The stand had a flange welded to it that is in turn bolted to the aft face of the aft cabin. There is a hole in that flange and a matching one in the cabin side. No need for any water proof gland with this setup. Any water that does get into the stand just drains out a small hole in the bottom.
Nice! Thanks, John…
Hi Marc,
I think that there is one more factor to consider in all of this that is a relatively recent phenomenon. That factor is solar panels. Many people find that the only realistic place to mount these is on the stern of the vessel. Do you have plans for panels? Unfortunately, things are often then mounted above the panels such as radar and wind generators. The small amount of shading that these provide really hurts the panel efficiency which means you get huge arrays to make up for the inefficiency. This doesn’t mean you can’t have both a radar and solar aft but it does mean that you need to be really careful about putting the radar in a place that won’t shade the solar. I know of at least one boat where removing a wind generator mounted higher than solar panels actually resulted in a net increase in energy produced because the solar efficiency went up so much. Venturing out into rough waters, a lot of care needs to be taken to make any solar array seaworthy but one of the biggest things is keeping the size down which means eliminating shading. In the grand scheme of things, I would consider radar much more important than solar provided you have an inboard to charge with.
We have our radar on the mast (fairly low) and it works for our usage. My biggest complaint is that it is fixed but most foggy days are accompanied by a lack of wind. We could mount a pole at the stern but our boat is aft cockpit and things are already busier back there than I would like. If we had a bigger, center cockpit boat, I would absolutely consider a pole.
Eric
Hi Eric,
Now there are a lot of good points. I had never thought of the solar shading issue.
Just one thought. As you say, in Maine fog is accompanied with a light or no winds, so radar tilt not required. However, in Nova Scotia and Newfoundland, fog and quite a lot of wind is common.
Hi John,
I am interested in your reasons for preferring pole to mast mount for a radar scanner. Ours is mast mounted, but I estimate that more than half are pole mounted at stern. The only reasons I can think of for preferring one to the other are: pole doesn’t interfere with foresail; pole does have a blind spot direct ahead.
I don’t intend to change, but it would be interesting to hear the opinion of an electronics expert. I know, you don’t claim to be one, but you are certainly more than a layman.
Yours aye,
Bill
Hi Bill,
Just scroll up to the article above, all my thoughts on the subject are there.
Is there any concern with radio waves or radar waves constantly hitting you from behind. I have a center cockpit boat and it was a concern I was considering. Whereas radar mounted on the Mast would not pose the same potential Problem
Hi Steve,
The safe distance on most conventional (magnatron) yacht radars is about 1 meter, if memory serves, and the new radars are much less powerful and therefore safer. as I understand it.
Having said that, I think that minimizing the RF one is exposed to is always a good idea, so we made sure that our radar stand is high enough that the beam is over our heads, at least when sitting.
This is relatively easy to calculate: just look up the vertical beam width of your radar in the manual and then draw it out on a plan of your boat.
By the way, we also put the radar in standby when reefing or doing other tasks that would put us in the way of the beam.
Having said all that, I’m going to guess that most experts will say we are being way too paranoid and that as long as you don’t get closer than a meter, you should be OK.
Anyone out there have any specialized knowledge of such things? I’m definitely winging it here.
John,
Thank you very much for the response.
I am new to radar and while trying to decide where to put
It I am trying to get all the info I can. It seems
To be there allot of great opinions out there
But none of the ones I have read addressed this issue.
I just purchased a Raymarine digital scanner and I want to
Put it in the best spot. Thank you again for the
Feedback
Steve
Take all of the following with the knowledge that my partner and I are very new to sailing/cruising.
Not a criticism, but merely a request for more information. For “the most important piece of electronic equipment on Morgan’s Cloud”, there is not very much information that I can find in your books or posts on radar.
Currently we have a fairly solid Furuno 1824C with NAVnet VX2. However, it’s also a big honking CRT installed down at the nav station and not visible from the helm. The Antenna is located on the mast.
I want to get a system that will overlay on my plotter and I’m really excited about the capabilities of Simrad’s new Halo system. The stern pole looks like the perfect solution to mounting an open array on a sailboat. I’m still trying to talk with an Edson rep to see if their tilting system could handle a 4ft open array like the Halo.
With the current radar systems, would you still elect to go with a dome on your stern pole?
I’m thinking that overlaying the radar on the plotter might help show if the chart doesn’t match the physical land as it should.
I also am interested in tracking squalls to help warn us to reef.
Anyway, perhaps after you finish the fabulous MOB series you could write something on how you use radar.
Hi Bob,
Here is my take on this this question, hopefully it is helpful to you. Like everything on a boat, the selection of radar is a compromise. What you should do is figure out how you will use radar then write down a set of requirements for it. People will often miss some very important requirements that are more system level thinking than component level. For example, you should have a weight requirement but this requirement actually has at least 2 inputs. The first input is the obvious structural concerns for mounting. But it is equally important to understand what the mass does to the overall mass of the boat, the trim, the polar moment of inertia about the pitch axis, etc. You might also think about servicing the unit. I believe what you will find is a set of requirements that are somewhat conflicting and then you need to make the performance, size, cost, etc tradeoffs for you.
We typically use radar for a combination of navigation, collision avoidance and weather. When we are using it for navigation, we are typically looking at coastal features that are relatively close (you need a very narrow beam width to pick up a coastline well at large distances) or we are trying to find a buoy that we used our GPS to get near. For collision avoidance, this can range from trying to find a spot to anchor in the dark and fog among other boats to keeping a watch when offshore. For weather, we are typically trying to watch thunderstorm activity. I would say that we typically use the radar on a 0.5-3 mile range for navigation, 0.125-6 mile range for collision avoidance and 6-16(our units max) mile range for weather.
As someone who has used both small and large radar arrays a bit, there are major differences in them. The larger arrays have narrower beam widths and more power which give you a clearer return off things. On large, stable vessels this is great but most people on this website will be on small sailboats that have significant motion and heel. I can say from experience that a 4′ open array that is rigidly mounted on a large sailing vessel does not work well when heeled over. A 2′ closed array that was gimbaled would have given much better information to us. Realistically, I don’t think that I could make use of the extra performance of a large array on a cruising size sailboat.
For our boat, I would never get a large open array unit. I really dislike the current trend of hanging huge amounts of gear off the stern of boats as it has many negative effects on the boats handling and the enjoyability of the cockpit that people seem to be unaware of. Also, to take advantage of these large unit’s capabilities, they become real power hogs which would require us to charge the batteries with the engine a lot more. I actually have the radar on standby instead of transmit during night watch most of the time when we are not near land with a couple of scans every 10 minutes just to save power. Finally, open arrays catch and wrap up lines remarkably easily which is the reason why you often see stainless rings around them. Domes are simply open arrays with a dome around them. For our own boat, I also like having the radar on the mast as it keeps the weight aft and prevent shading of our solar panel but it means we can’t use a leveling mount. If we owned a 60′ powerboat, our requirements would likely be very different and we might well use a large open array.
When our current unit dies, I will be looking hard at the broadband radar offerings as they have a much better image in close and use about half the power. They do sacrifice some things such as range but we very rarely use more than 6 mile range anyways. I do like the overlay features but will likely still maintain the ability to run the radar as a standalone unit.
Eric
Hi Bob,
Not a lot I would add, on a technical basis, to what Eric wrote above—he is always worth listening to and probably knows more about it than I do, although I don’t like on mast installations, so I differ with him there.
Having said that, your question did inspire a post. In fact I just wrote part one. Look for it soon…just as soon as I get my head out of Cascading Style Sheet hell (the new web site design).
Hi Bob,
First part of my thoughts on marine electronics is up. Second part with some specific recommendations in a week or so.
To follow-up. I talked with a rep at Edson and he said that their mount was not designed to handle the weight of an open array antenna. 🙁
So the choice is to stick with the normal small dome array, go with a solid, non-tilting mount, or cobble something to do the job.
I’m now researching how well the 4G domes do on rain squall tracking.
Before reading this I was going to skip the addition of a manual tilt adjustment. As I read a few posts on forums that said it really doesn’t seem noticeable. And the “probably motoring” in fog theory as well. But we are sailing out of Sambro, and it seems prudent to spend the extra time building in some kind of tilt device. Even though I really just want to get this job done sooner than later…
-Chad
Hi Chad,
Good to hear it was useful and I think you are making a good call on going to the trouble of installing a tilt device, particularly because, as you know, we often have wind and fog at the same time here in Atlantic Canada.
Hello Chad
Did you ever build a tilt device for your radar? If yes I would be interested in how you went about it. I am thinking of doing the same.
Barry
Hi John, would an aft mount radome on a pendulum be good for the furuno 1835 radome instead of the actuator system that you have? If it is on a pendulum, it will always aligned to the horizon isnt it?
Hi Ei KIat,
I’m not a fan of pendulum systems. Just too much flexing of the radar cable for me to be comfortable with the idea.
Hi John, By flexing, do you men cyclic fatigue stress on the radar cable? If there is an engineering solution to this, are there any other disadvantages to the pendulum system mounted on a pole? There are a lot of oscillating machinery out there and they must have a solution for “flexing” cable. I have not used a radar before and in my simple mind, the pendulum system mounted on a pole is self levelling, low maintenance and doesnt need to be attended to frequently in a rolling sea must be the “best” system if the issue of “flexing” cable can be addressed.
Hi Ee Kiat,
I have never owned one, so I can’t tell you what the drawbacks might be, other than the cable. As to a solution, I really can’t see one. The point being that the cable being used is that supplied by the radar company and I’m pretty sure that they would not design it to withstand many hundreds (thousands?) of flex cycles an hour, even assuming that were possible.
Bottom line, to me at least, radar is the most important electronic device on the boat and so I will not take any risk of compromising its reliability.
Hi Ee Kiat and John,
Most good wire manufacturers will rate wire for cycles if it is intended for a cycling application. These ratings are based on the wire being appropriately constrained in something like cable chain so it can be hard to apply the ratings to some applications. I have actually been pleasantly surprised at how well wire stands up to flexing and how high the ratings are. As you would expect, the thing that kills everything is if the bend radius gets small. All that being said, I am not optimistic that you will be able to find the rating on the wire used for radars although you might.
There are fancier solutions for this such as slip rings but I would not want to get involved in any of that in this application. A great example of how this is handled in industry would be robotic arms such as the Kuka. Most of the cables are run inside of cable carriers (basically flexible conduct) which help maintain bend radius and then those carriers are carefully attached at certain points. They also run the cables outside of the arm specifically to stay away from the tight bend radii at the joints that would be necessary if run inside. Robotic arms with swivel bases usually have circular cable chain at the bases that allow large angulation which would be impossible with a small service loop. If you want to go down the rabbit hole on this, there are companies that have whole product lines on cable management such as IGUS.
I realize that this doesn’t answer the core question of whether radar cables will take years of flexing but if I wanted to figure it out, I would start by seeing if I could find a rating for the cable and then look at the bend radii and expected number of cycles.
Eric
Hi Eric, thanks for the post. And yes, i was thinking of robotic arms in the industry that turns over 180 degrees and how they overcome the problem of flexing. I havent got to that part of technology/engineering yet ! There seems to be 2 schools of preferences in this post with regards to gimballed radome ie mast mounted (usually ungimballed) and pole mounted (gimballed and ungimballed). I have not used radar before and I am really trying to get a picture of how much compromise are we talking about when heeled over. I try not to sail over 15 degrees heel and max heel for comfort would be 20 degrees for the family. I try to keep the boat flat if i can help it. Yes, working on all the compromises… power drain.. weight distribution… Thank you all for your helpful comments..
Hi Ee Kiat,
If you are sailing at 15 degrees of heal and don’t have a tilting radar your ability to see a target abeam will be much compromised to a point that in thick fog it will be dangerous. (I have tested this.)
Note that MC, particularly with her carbon mast and easily driven hull tends to sail at lower heal angles than most boats, and I would not be without the inclining radar.
So you need to ask yourself where you will sail and will you be willing to sail, or at least motorsail, to keep the heal angle under about 7 degrees when in fog. If the answer to that second question is no, and you want to sail in places like Atlantic Canada were we get thick fog and wind, you need an inclining radar.
Hi John, point taken. Thanks.
Hi John, I am working on the height to mount my radar on a pole at the stern with regards to radiation avoidance. The data provided for the radome states :
Beamwidth (nominal): Horizontal: 4.9° | Vertical: 20°
To calculate where the beam is transmitting from the stern, I suppose I should use the 20 deg angle on the vertical plane and make sure the -10 deg below the horizontal plane clears 2m above the bow of the boat (assuming a crew standing at the bow). Am I working this out correctly?
I am also curious as to why the horizontal beam is 4 times less than the vertical beam as I would think it should be the other way round as one would like to see more of the sea than the sky… Am I reading the beamwidth data correctly?
Do you know what does “norminal” means in this context? I thought it should give us the maximum..
Any advice on this would be most appreciated. Thanks.
Hi Ee Kiat,
I’m no radar expert, but I have set up my radar so the vertical beam (-10) clears people in the cockpit. I have not worried about crew forward although we do go to standby when reefing or otherwise at the mast. That said, I think I’m right in saying that the power of the radar falls off with the square of the distance so we are probably being a bit paranoid with that precaution.
Hi John, I am deciding on the size if the pole to mount my Raymarine Quantum2 radome. May I know the reason for such a beefy pole on MC? I was thinking of a2 inch stainless when I had a closer look at the size of M C radar pole. It must be at least 3 or 4 inch. it also appears that most images of sailing boats with a wind Generator and radar in the internet, the radar pole is always the larger of the 2. I would think that it should be the other way around as the drag and weight of the wind gen. will be larger then the radar. Would you be able to shed some light?
Hi Ee Kiat,
Our pole is aluminium, so that’s one contributor. That said, even at 3″ diameter (if memory serves) it needed a couple of braces to stop it vibrating a lot when it’s gusty. Point being that I think bracing is more important than pole diameter.
I have bought a Furuno 1831 radar with dome, but for our Alpa 11.50 seems overdimensioned both for the screen and for the dome, that perhaps with it’s diameter is more adapt to a 45-50 foot sailboat.
Do you agree ?
Hi Michele,
I guess you bought the radar second hand, since I think I’m right in saying that the 1831 was discontinued a couple of decades ago? I’m assuming you bought it with the 24″ closed array and in that case I think that the type of radar you buy is more a function of where you sail, how much of the time you will be operating in fog, and how much traffic and debris you will be dealing with, rather than boat size. Larger scanners resolve better and so the operator is less likely to miss a target. So I guess the issue is that if one hits something, or is hit, because the scanner was too small the size of boat won’t much matter.
All that said, although I have not used one personally, I believe Furuno’s 19″ scanners do a pretty good job. You might look at: https://www.furuno.com/en/products/radar/MODEL1815
If you do keep the 1831 make sure you check the age of the magnetron and replace it if in doubt.
Being able to point well in light air is very important to me. Also shading the aft mounted solar panels with a dome shadow seems important. Would mounting a radome about 3-4m above the cabin top disrupt air across the main enough to make any difference? Is shadow on the solar a real problem?
Hi David,
On the mounting, do you mean on the front face of the mast? If so, and windage is a negative, particularly in front of the main, that said, if you are not racing I don’t think the difference will be noticeable from that one change. Performance, particularly to windward, gets screwed up on cruising boats when we just keep on adding windage, cockpit enclosures, radar, wind generators, stuff lashed to the life lines, excessive solar arrays, and on it goes.
Of course all those things have benefits, but too many of them is a problem.
And yes, the shading from a radar unit will make a big difference to panel output. This can be ameliorated somewhat by wiring the panels in parallel, but that has the drawback of doubling the wire gauge required to reduce voltage drop.
In summary, it’s all tradeoffs.
I knew I’d find intelligent input on this topic. Fitting out 1978 NY 40 (Doug Peterson vintage IOR design) for transatlantic cruising. Was about to go with backstay mount until a buddy at a boat yard told me 2nd hand talk of RF issues etc. I can’t see how that would play compared to pole or mast mount. Also reading excellent thread; only negative was about bending cycles of cable which is easily mitigated by long radus bending if not a full loop which could later be changed shorter to double the wear time plus leaving extra 12″- 18″ below deck for future off season pull up & re- terminate cable. As these ends can be changed. Is there any more ” anti- backstay ” arguments against something like that gimbal mount Questus other than cable fatigue? Appreciate all this knowledge out there. Great community. So glad I joined!!
Hi George,
After talking to a bunch of people with backstay mounts I still prefer pole mounts and have gone that way for our J/109.
One of the things I learned is that back stay mounts are a pain to keep aligned and working properly if the leach of the mainsail requires the scanner to be behind the backstay. The other issue is these units are a pain to assemble and disassemble when stepping and unstepping the mast. To me a pole mount is just simpler, cleaner, and generally lighter. It can also be used for mounting other stuff and as an outboard crane.