Mounting heights for antenna/radar on new radar arch

I just installed a new custom radar arch from Atlantic Towers (about 4 hours with 3 people) for Mirage, a 1976 43' DC I bought in November. Going to load her up with new electronics as well from Garmin (a GPS 4212 for each station, GSD 22 depth sounder, XM Weather/Satelite, GMS 10 network hub, and GMR 21 radar) and Shakespeare 2030-G TV Antenna. I have 4 antennas I intend to install on radar arch (Radar Dome, GPS, XM, and TV) and plenty of room (3 platforms on arch). What I'm wondering is if there is a best practice for moutning heights of these items (i.e. GPS Antenna above Radar Dome, TV Antenna below Radar Dome, TV antenna as far from radar dome as possible, etc). Any advice is very much appreciated!

There should not be any problems mounting the antennas in any order you want. The radar should be centered. There could be a blind spot where you mount the TV antenna depending on its size. As long as it is not a great big dome there should not be any problems. All the antennas are on different frequencies and they are enough away from each other on the spectrum. Good luck. I have been thinking about putting a arch on my 43DC. What model did you get? And if I dare ask what did it set you back. Also did you mount it to the hard top or the fly bridge sides.

BILL

Unless I misunderstand, the angle off level, fore and aft, will be the primary consideration for mounting the radar. The earth drops 6 inches/mile, so from the arch the radar will about 15-16' off the water, aka a theoretical horizon of 30-32 miles or so.

If aimed high, it will be above the horizon and if aimed too low, it will look out only a few miles. Actually the radar is most handy when running in foul weather and maybe less than full cruise and this is based on running my 43'DCFB, a very similar craft. So it should have some adjustments made and the mount should allow that.

I prefer to be able to look out about 12 miles at 9 knots (hull speed and off the step, i.e. off plane). As you speed up, the bow will rise and the radar will look further out, which is good. But maximum resolution is important so aiming lower is better IMO. I sometimes return from a cruise in the dark into a river channel with lots of small fishing boats, so I like to be able to spot them on radar; this combined with the spotlight. When idleing in to avoid (absolutely) hitting one of them. And they don't all run running or anchor lights as they should, so you are on your own on seeing them!

When it comes to the other antenna, I would prefer at least four radios, and each should have its own antenna. So two radios below and two on the flybridge would result in four antenna mounted probably on the flying bridge. Again, due to the horizan, the higher they are, the more they are affected by rolling, so very high mounting is less important than stability for a stable signal. Usually one of the 5' or so models of sticks should be good.

P.s., I would love to have an arch at some point. If its possible to pimp out a 43'FBMY that is a cool way to do it!

I installed an Atlantic Towers Arch on my 48 YF and have been very satisfied. (That was after they sent me a wrong sized arch, but took it back no questions asked.)

Two general suggestions: If you boat in an area with a lot of thunder/lightning, consider drilling and tapping one leg of the arch and add a stud and add a wing nut so you can easily attach a grounding cable with a big weight (maybe a zinc) to hang over the side. A square foot of underwater surface area is recommended. (I tried a copper flashing square and the first thunderstorm blew it out of the water.)

You can also add a lightning rod higher than your antennas. If the arch is anodized, polish it with wax or boat polish to keep it shiny and smooth for an extended period. Rinse off salt spray.

When you snake wires DOWN the arch tubes, insert at top, extract at bottom. Connect two lines with the first wire snaked thru...then each time you run another lead, add the next piece of line...that way you have to snake onl;y the first wire...and keep a spare line after you last rune...then you'll be ready for the next when you add something else....maybe you can run multiple antenna leads at one time on a single line.


I'd make the other antennas either higher or lower than the radar if possible...My TV antenna for example is close to the radar but about a foot above in height. There are guidelines for mounting duplicate antennas that will be in simultaneous operation, say two VHF antennas, but different devices on different frequencies seem to do generally ok.

After mounting your radar, be sure to test align it on a target directly ahead and if off a bit, adjust it electronically via the set up menu...it would be embarassing to run into a buoy or another boat in dense fog.

Thanks for the replies. I just got done reading Nigel Calders "Boat Owners Mech and Elect Manual" and was wondering about grounding the tower for lightening. I like your solution to it. I did not know you could adjust radar internally (thought it had to be manually shimmed for any type adjustment).

The boat was on the hard when we installed the arch last weekend so I hope we got it level. They (Atlantic Towers) made mention of it somewhere that it is better to get the arch ascetically pleasing and then shim the radar to compensate for happy compromise between plaining and idle. I had the arch custom made (they have the template for the 43 DC on file so they didn’t come out to measure) for $1699. I added the anchor/nav light for $139 so I could remove front mast and also the rear spot lights for $99. I live on Long Island so they delivered for $100 cash from NJ (whole thing delivered $2037). They would do the install for $350 as well, which I would have done had I known what a pain this was to install. I installed as far back and high on fly bridge sides. Guy who delivered it apparently worked for Atlantic Towers and recommended the spot – said you want the legs of tower as short as possible as it will be more rigid (even though custom made, you still have to cut the legs to fit yourself, getting the height and position right is what is such a pain in the ass). Best piece of advice he gave me was to buy ratcheting tie down strap to pull legs together (not mention in instructions – great video how to install at http://atlantictowers.com/at_sub/install_fr.htm). You have to pre-stress legs to add rigidity to structure as well as to get mounts to line up. I initially had delivery to my house thinking I could put on top of minivan to bring to yard – nearly had a heart attack when I saw the size of this thing. It only weighs about 120 lbs, but awkward. Paid them an extra $40 and they brought straight to yard where we left on front of boat until I installed. This is definite 3 person job (4 too many as fly bridge too small for that many working people). Also, for getting at nuts on back plate of mounts, I opted to install 6” speakers in the holes (will add stereo later) I had to drill for access. Definitely does pimp the boat – brought her from the 70’s into the 90’s

I am new to radar and definitely worried about the 21” TV antenna causing a big blind spot. Been caught in fog enough mornings between Montauk and Block Island and came in more than a few times to Mattituck inlet at night (no lights on beach or jettys) on my sailboat with nothing but handheld GPS that only gave lat/longitude to really appreciate the added security of radar and chart plotter. Great info on GPS and XM Antennas as well – I will line them up in tangent to radar view so at least I should only get 1 small blind spot. Maybe I have enough room to mount TV antenna on underside of arch? That would take care of problem (and potentially create a new one if not tv antenna housing not water tight from underside).

I had Atlantic Towers install in arch on our previous boat - also in Long Island. They came out, measured, then came back out and installed the arch. Did a great job and though I usually do all my own work, it was well worth it. I wouldn't hesitate to use them again if I wanted such work.

If your TV antenna is a satellite tracker, you want to keep it out of the radar beam as best you can. We installed a KVH and have it about 8' forward and a couple of feet below the 48 mile open array. No problem. But the KVH rep warned that a strong recreational radar signal can fry a component of the KVH.

Bob