Optimal Mounting height for Radar

[AKfisher]

I just purchased a new DRS4D NXT and I plan to mount it on my mast about 5 ft higher than my current radar is mounted...to about 20 feet off the water. This will totally clear hard stays and other obstructions besides the mast itself which I should clear by a meter. However moving it higher raises a couple of questions for me.

Can a realatively small increase in height affect the radars ability to see very close in targets? Is there an easy way to calculate this? Ability to see targets as close-in as possible is a top priority.

Does a higher mount mean less effective radar when rolling or pitching in heavy seas? Do the nxt radars compensate for this effect?

 

[Quitsa]

In concept you can enhance close range performance by using a down angle on the radar mount and “aiming the center of the beam closer to the bow. The higher your mount, the more you would have to angle down. With a 24 degree vertical beam, at 20 feet high, with a level mount the lower edge of the beam would be 94 feet forward of the radar. With a 5 degree down angle, it would be 65 feet. In real life, the boat will not be stationary and might be pitching up and down from waves so the theoretical limit will move in and out.

The best way to get the result you wish to see is to choose a moderate down angle of 2-3 degrees and try it out. If the close range performance is not what you would like, shim it down another couple of degrees and try again. Of course at some point you will harm the performance at longer ranges.

The good news is that solid state radars do not suffer from the large main bang of magnetron radars and have much shorter minimum ranges. Also with a sailboat you don’t have to worry about the big changes in running angle experienced with a planing hull powerboat. For example, my boat goes from running flat at 6 kts to a bow up attitude of 6-7 degrees at 10-12 krs and down to a bow up attitude of 3-5 kts at higher speeds. Thus inevitably there is a compromise in choosing the right mounting angle.

 

[AKfisher]

That's very helpful info! Thank-you.