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Old 13-10-2010, 18:08   #1
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Radar Mast Pole Height

I have a 2kw 18" dome, trying to figure the height off the deck it has a 25 deg vertical bandwidth,

So it would have a 12.5 D downward beam, will the height above the boom matter?

I know it needs to be above my head but I don't want to use a taller pole than needed.
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Old 13-10-2010, 18:28   #2
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The boom will definitely block, or attenuate, targets. I'd mount it a couple of feet above the boom height. Radar 'sees' much like your eyes. Mount it where you can reliably see stuff. Of course when heeled the boom may again block the radar, but usually there's enough rocking to have it out of the way some of the time. An 18" unit will see pretty well around the typical mast.

8 or 9 feet above the cockpit sole should do it.
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Old 13-10-2010, 18:33   #3
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That would be about 6' above the deck then.


I also saw the dome can be tilted up 5 deg with no effect?
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Old 13-10-2010, 18:49   #4
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Heeling does attenuate the signal. I suppose the 12 degree spec is the half-power point. So it will help to keep the heel less than that to really see stuff. Reef early. You can buy a radar mount that swings or adjusts, but I wouldn't.

In the fogs of California there is typically little wind...no heeling. In the squalls of SE Asia the rain completely attenuates the signal. It's always something.
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Old 13-10-2010, 19:54   #5
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6' above the deck only?

I think you will be shooting thru the eyes of anybody working on the deck.

b.
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Old 13-10-2010, 20:00   #6
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Height depends upon the size of the boat and the boom height. As stated by others you want to get the antenna above the boom enough so that when heeled the boom will not be "shading" the signal. The height of the pole is limited by the diameter of the pole and how rigid you can make it with various supports. You don't want the radar unit wobbling on the end of the pole like that circus guy with the spinning dishes on top of thin rods/sticks.
- - Why not mount the radar on the front of the mast? If you look at sailboats when the sails are out, there is a open area from about 1/3 to 1/2 the way up the mast. The foresail never gets/extends into that area.
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Old 13-10-2010, 20:27   #7
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No intention of using the mast.

I found an online calculator for every 12" the drop down of the beam 12.5 degrees is 2.66", so 10' in front of the radar pole of 6' the beam is at 3.44' above the deck.

If 8' that's 5.44" at 10' in front

Now if the dome is titled up 5 D, big difference.

At 6' 1.62" drop or 4.38' above the deck at 10'

A 8' pole = 6.38' at 10' in front


Does this look correct??

.
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Old 14-10-2010, 04:24   #8
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The only danger from a 2kw pulsed radar would be to the eyes if you stared directly into the centerline of the antenna for a long period of time at less than 3' with the antenna NOT rotating. Otherwise, the danger is nil. You could really put it anywhere you want, but normal practice for pole mounting is to put it at least above head height. Obviously, the higher it is, the longer your range. In your case, 7' to the bottom of the radar housing would be fine.

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Old 14-10-2010, 05:21   #9
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No intention of using the mast.
Why not? Surely, the higher the better?
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Old 14-10-2010, 05:31   #10
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"Higher the better" is better for the radar. Maybe not for the overall plan. I certainly wouldn't want all that junk way up there. The benefit is not that great. I don't get much use out of 24nm targets anyway, that's an hour away. I only need the 2nm and less ones.
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Old 14-10-2010, 05:36   #11
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Any weight aloft is a big negative (not only the unit but the bracket and cable), holes in the mast for mounting, the windage on the slot, just an inefficient location, spinnaker interference, to me just not pleasing to the lines of a boat and maintenance.
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Old 14-10-2010, 05:50   #12
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a little scared of the bosun's seat are we.....
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Old 14-10-2010, 06:39   #13
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"Higher the better" is better for the radar. Maybe not for the overall plan. I certainly wouldn't want all that junk way up there. The benefit is not that great. I don't get much use out of 24nm targets anyway, that's an hour away. I only need the 2nm and less ones.
an hour away for you but not for guy tracking you in a powerboat.......
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Old 14-10-2010, 06:42   #14
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Hi all: saw somewhere a removable unit mounted on the spinnaker track and only installed on an as needed basis,this solves the legimate objections of weight aloft ,esthetics, etc.. Might try this myself some day.
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Old 15-10-2010, 17:04   #15
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Hmmm,

Seems to me that when heeled the boom (usually on the leeward side of the boat, isn't it?) is now lower than the horizon, and hence not an issue in obscuring the radar.

On our boat, the PO mounted the radar on the arch, but BELOW the solar panels, and directly in line with the boom. Very bad choice! When heeled, the panels block the radar beam on the leeward side, and when not heeled the boom blocks forward view.

I for one much prefer the mast mounting, and am considering making that change on Insatiable II despite the cost and inconvenience. Of course, we've owned her for over 7 years now and it hasn't yet happened...!

Cheers,

Jim and Ann s/v Insatiable II lying Sunday Ck, Hinchinbrook Channel, Qld, Oz
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