Q&A: Radar Scanner Position

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:

  1. The scanner is much less vulnerable to damage from an errant halyard or sail.
  2. 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.
  3. A scanner on the mast is more difficult to service than one on a pole and heaven help you if the cable needs replacing.
  4. Mast mounted radars are very vulnerable to damage when the mast is un-stepped.
  5. 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 a fraction of what 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.

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Meet the Author

John

John was born and brought up in Bermuda and started sailing as a child, racing locally and offshore before turning to cruising. He has sailed over 100,000 miles, most of it on his McCurdy & Rhodes 56, Morgan's Cloud, including eight ocean races to Bermuda, culminating in winning his class twice in the Newport Bermuda Race. He has skippered a series of voyages in the North Atlantic, the majority of which have been to the high latitudes. John has been helping others go voyaging by sharing his experience for twenty years, first in yachting magazines and, for the last 12 years, as co-editor/publisher of AAC.

19 comments… add one
  • Marc Dacey Oct 28, 2014, 11:26 am

    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.

    • John Oct 28, 2014, 12:19 pm

      Hi Marc,

      Yes, on a pole is way better than on the mast in my opinion. The arms are from Edson.

      • Marc Dacey Oct 29, 2014, 7:15 pm

        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?)

        • John Oct 30, 2014, 7:54 am

          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.

          • Marc Dacey Oct 30, 2014, 3:34 pm

            Nice! Thanks, John…

    • Eric Klem Oct 30, 2014, 9:34 am

      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

      • John Oct 30, 2014, 12:40 pm

        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.

  • Bill Attwood Oct 28, 2014, 2:39 pm

    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

    • John Oct 29, 2014, 8:16 am

      Hi Bill,

      Just scroll up to the article above, all my thoughts on the subject are there.

  • Steve Frank Nov 5, 2015, 6:17 pm

    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

    • John Nov 6, 2015, 9:56 am

      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.

      • Steve frank Nov 6, 2015, 10:45 am

        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

  • Bob Muir Jan 7, 2016, 11:51 am

    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.

    • Eric Klem Jan 7, 2016, 3:15 pm

      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

    • John Jan 7, 2016, 5:08 pm

      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).

    • John Jan 8, 2016, 6:10 pm

      Hi Bob,

      First part of my thoughts on marine electronics is up. Second part with some specific recommendations in a week or so.

  • Bob Muir Jan 7, 2016, 12:31 pm

    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.

  • Chad Jun 18, 2017, 3:30 pm

    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

    • John Jun 19, 2017, 8:06 am

      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.

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