mast mounted radar

[Paul_L]

Originally Posted by sailaway21

If Paul has seen containers carried ten high on deck I'd certainly like to see a photo of them loaded thus. (!) (Five high is common with the top tier being empties, seven high aft only if they're empties after two high. Each container is 8' high.)

I could have sworn that I counted 10 high stack on one of the giant container ships we passed last summer. But that is not the point. I used 150ft as the target height in my distance calculations. In the response to that it was implied that I was stacking the deck and that 70 ft should be used so the results could be used to come to a different conclusion. I just checked the height of the Panamax container ships, not the biggest container ships but very common, they are 190 ft tall. So using 150 ft in the calcs is reasonable.
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To add to what MaineSail has posted, once again, it's hardly the norm that you'll pick up a target on each sweep of the scanner, especially smaller targets. This has two impacts on how you use your radar in practice. The first is that you realize that, no matter how sophisticated your system, you are going to lose targets or experience spotty reception. This is the difference between what the manufacturer and his engineers tell you and real world performance.

Exactly, understanding the limits of your tools is important. If two boats travel through the night in rough conditions and one sees 5 target through the night and the other sees 3, which one is safer? The one in which the watch standers understand the limits of the radar and that there was really probably 10 targets.

Your comments on needing multiple sweeps for accurate ARPA are true, but they also apply to non-ARPA case. In the typical mom and pop cruising case you can't have a dedicated person on radar watch. Targets need to be visible in multiple sweeps to get reasonably detected. A radar high in mast on a small boat will roll and pitch widely, reducing its ability to get multiple sweep detections. A radar mounted lower on pole will roll & pitch less, but get hidden behind waves more reducing its ability to get multiple sweep detections.

Mounting a radar high on the mast in a small boat will increase range. This increase is not as far as many think, but it is significant. A 24in radar will discriminate targets significantly better than 18 in. A 48 in will beat a 24in, but isn't appropriate for a small boat. Weight and windage in the rig causes negative affects on sailing and stability of sailboat. A radar mounted on a pole or the mast will work fine on a small boat.

Where you mount yours is no business of mine.

Paul L