Radar Transceiver Positioning

[webbwash]

So who amongst us is so familiar with the placement of radar transceivers that can quantify what effect the placement of a radar installation behind the blind of carbon fiber masts and sails will incur.

We know that the radars previously were placed as high on the forwardmost mast as possible with the wooden and aluminum spars. Current design philosophies put the radar on a separate stalk mast or bridge over the cockpit of a "modern" sailboat. However, who has done the homework to calculate the effect of these placements on current sail and mast technology.

Interesting thought?

[Greybarn]

We build sailboats between 30 and 60 feet in size. We see no difference in the shadow between aluminum and carbon masts with the radar mounted at the lower spreader. We also don't see any difference between dacron or any kind of laminated or molded sail.

[marshmat]

I suppose there would be variations depending on the exact nature of the materials used.... but navigational radar beams, for both aircraft and boats, will generally not be affected too much by carbon. The radomes themselves are often made of carbon on aircraft. Among the main factors at work here are getting the radar high enough and stable enough to have a good view, and getting its powerful beam well away from soft squishy living things such as crew members. If the rigging's gonna screw up the radar, it'll screw it up no matter what mast or stalk the thing is mounted on, the only difference will be which sector of the unit's sweep is the most screwed up.

[kenJ]

This is from the Catalina 34 site. He did a lot of research before he decided to put it on a pole at the stern. Personally, mines on the mast, out of the way, enough clutter at the transom.

I was confused only about one thing. Why did people mount their radars way up on their masts 30 and 40 feet above the water line. I wanted to use MARPA and collision detection so I needed to do some math and figure out the best height to mount a radar, that is unless I wanted to do weather forecasting.. Hee...Hee.

R2 = rä2 + (rä + H)2 - 2rä(rä + H) · cos α

Here is a link to my excel spread sheet I calculated based on the curvature of the earth: http://www.pc-land.com/simplelife/Radar2.htm

Heres one at zero object height that is easier to understand and figure with: http://www.pc-land.com/simplelife/Radar3.htm

Heres one with an object height of 10 feet and a radar height of 30 feet: http://www.pc-land.com/simplelife/Radar4.htm

The problem with the radar at 30 feet is the huge blind spot around your boat.

You will see that a radar height of 11.5 feet off the water and an object height of 10 feet off the water the radar range based on the earths curvature is 8.03 miles and an object height of 0 feet the range is 4.88 miles at a radar height of 16 feet.

The radar transmits its radio waves at 12 degrees angle above and below the center-line of the radar and so at 11.5 feet the radar just missed the bow of my boat. Perfect! and still has good range.