Radar wedge - a further explanation

M

maryswensen

New member
Having not received a reply to my original request regarding the radar wedge, I am going to hopefully clarify my question. We have a new C Dory 22 and have read that the bow does rise quite a bit. We are adding a radar unit and wonder whether or not a wedge is required to compensate for the bow rise. The antenna will be a roof mount on a five inch stand.

All thought will be appreciated!

Best

Mary C.
 
Technically a wedge will improve forward looking radar on the C-22. Mine is 4 degrees and is built into my radar mount. Personally I don't think it makes much difference within a mile or two though, and that's my major concern. If memory serves me, the transmitted lobe on a typical 2k radome is 5 degrees in the vertical plane but it's a lobe, so you're gonna get most everything you need from the power contained in a fairly wide section contained in the lower half of the lobe. I've observed the small Coast Guard boats operating around here and tied up to my marina pier and none have a wedge. YMMV

Don
 
This has been discussed quite a bit in the past. The experts are probably cruising at the moment. Check the discussion HERE and lots more HERE. Your tower may well have 3 to 5 degrees of dip built in, many do. Whether it does or doesn't, it will work fine.

Regards,

Mark
 
And just as a point of comparison, sailboats routinely mount the radome on a fixed mount, and then sail heeled over 10 to 15 degrees without any significant degradation in radar performance.
 
We also have about a five degree wedge with our radar, but as the others have said, for short range work it is probably unnecessary. Also, we have two uses for our radar -- night or fog, and then we are usually traveling slowly and the wedge is probably not needed since the boat is near level -- and the second use is in storm, and then we're slow by definition but pitching about like on a bucking horse, and that five degree wedge is up there on the cabin roof chuckling at us.
 
The 5 deg wedge, if nothing else, makes it look 'proper'! Didn't do a comparison with/without the tilt, but I can see those low bouy markers in the marina channels 50 ft in front of us while going out or coming back! Of course like El/Bill said, you're mostly level at slow speeds so the antenna's vertical beam should provide enough to see what's ahead. I'd just rather give the antenna all the chance it can get to see straight ahead without relying on beam width, etc.
 
The vertical beam of a radar is between 25 and 30 degrees. I have never used a wedge in any of my boats, including the 3 C Dories I have owned. Some boats which run at a 10 degree angle, would definately benefit. But consider that in limited visability your speed will probably be slow (at least it should be)--and the boat will be running fairly level).
 
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