2kw vs 4 kw radar

jklewissf · #1 (**permalink**) 11-29-2002

I had a Raytheon RL 9 on my NorSea and was content with its performance on the few occasions I really needed it. I sail San Francisco bay and despite the legendary fog really felt the radar was more useful in mexico where the lighted aids to navigation dont always work.

Im moving up to a large boat and have been told that I should consider a 24" 4 kw radar. I have looked at the 4kw display and am not convinced it adds that much value for all the windage and cost.

Any input on this would be helpful.

WHOOSH · #2 (**permalink**) 11-29-2002

J:

At what height will your array be mounted? Using that and computing distance to the horizon, I''m guessing you''ll be well inside 10 NM. Add on some add''l distance for picking up a ship''s superstructure and you remain well inside the range of a 2kw 18" array in e.g. an SL72. IMO the advice you''re getting is one reason we tend to hear how much more expensive a bigger boat is than a smaller one - we upgrade the bigger boat because it''s bigger (not out of need) while tending to downsize things on a smaller boat, a good example being nav lights, as tho'' smaller boats need to be seen less or at less distance than bigger ones. You''ll get better between-target definition with the wider array at very close ranges but I find it tough to make a good case for a 4kw unit mounted 20-30'' above sea level.

OTOH the MARPA computational abilities of the upscale units are very impressive and provide add''l help to a short-handed crew. But you''re right - that''s substantially more expense.

Jack

windship2 · #3 (**permalink**) 11-29-2002

Isn''t it true that a 4kw is twice as powerfull as a 2 kw unit?
To me it''s not only about seeing the big stuff, it''s about seeing the small stuff too.Lobster pots moorings etc.
Wouldn''t a 4kw unit see the small things better?

Dennis

jklewissf · #4 (**permalink**) 11-30-2002

Jack,

It is my intention to put the radome on an arch about 10 feet off the water. I know that limits the range but dont want the weight or sail interference that a mast mounted radome causes. I had figured that the 2kw unit would meet my range needs under all but the worst weather conditions but wondered about the resolution advanatge of the larger array.

What you have to say certainly validates my concern that 2kw may be more than adequate for my needs and that the extra windage and expense is not justified.

In 1994 I did the single handed transpac and had my RL9 on board at the time. Range and resolution were somewhat of a moot point since the radar spent about half its time looking at the ocean and the other half looking up in the sky. Because of the motion of the boat I could not use the alarm zone feature of the radar most of the time at sea.

Most of the skippers on that race left their strobe lights on at night and one was spotted by a large commercial ship at 13 miles because of the strobe. They were in radio contact with the ship and he told them that, even though he knew where they were from the strobe, he was within 3 miles of them before he could pick the sailboat out of the sea clutter on his gigawatt radar!

Thanks for the feedback.

John

TDanz87646 · #5 (**permalink**) 12-02-2002

John
Don''t you know that it is against the rules to keep the Strobe on all the time. It is for emergency use only. If I saw your light, I would as is required to go to your assistance. Having got to your vessel and find out that you were asleep or drinking beer, I would if I had a gun shoot a hole in your hull. Wake up guys, and learn to sail.

RichardElliott · #6 (**permalink**) 12-02-2002

A mast mounted radome adds very little weight aloft and does not interfere with the jib when mounted near the spreaders, i.e. the spreaders clear the jib.

jklewissf · #7 (**permalink**) 12-02-2002

I am aware that leaving the strobe on is illegal. Most of us who did the single handed transpac that year decided that we would rather be illegal than dead so we left both the tricolor and the strobe on and left our vhf radios on so that anyone concerned about our well being could hail us and wake us up. If we were awake and able to maintain a lookout we turned the strobe off.

Several of the skippers of large ships that spotted boats in the race expressed approval of this decision. They had been told the race was headed to Hawaii and being able to see us at 10-15 miles was helpful.

All in all I think that single handed ocean crossings are more irresponsible than leaving the strobe on. I would not do that again.

John

windship2 · #8 (**permalink**) 12-02-2002

Is it true that the higher the array is mounted the more it cannot see close to the boat?
To me, bay and coastal sailers should not have their arrays high on the mast.

Dennis

jklewissf · #9 (**permalink**) 12-02-2002

I agree that bay and coastal sailors should have good radar visibility near the boat but that also seems like a good idea off shore too. You cant watch the radar constantly and I would not want someone to slip into my blind spot while I was not looking.

I''m going to mount my radome just high enough to prevent the beam from hitting me in the head.