I've never used "big ship" radar and I don't now the specs for them, so I'm curious if
they have the same beam width issue as recreational radar.

The Beam Width on the small Raymarine units is 25 degrees, which means there is a blind
spot with a radius roughly 5 times the height of the antenna. From that picture, assuming
a 50 foot mast, the radar looks about 150 off the water, which could imply the boat is
"below the radar" when its several hundred yards away.

In addition, radar usually "blanks out" the processing for very short range - I forget the
distance but I think it was around 50 to 100 feet for small radars.

So I'm curious: is it possible that a small sailboat could be "invisible" to radar once it
get close to a large ship?

jeff

"Shen44" wrote in message
...
Subject: Radar
From: "NH_/\)_"
Date: 08/28/2003 20:08 Pacific Standard Time
Message-id:


Thanks a reply I was waiting for

NH_/)_


"anonymous" wrote in message
.. .
On Thu, 28 Aug 2003 14:04:13 GMT, "NH_/\)_"
said:

The sailboat was small yes... but it still should have been
picked up
on radar. Somebody did a major F-up.

Having spent a few years on the bridge of a naval vessel I can tell you
that
sailboats often don't show up on radar. 'Course it's been a few years for
me, and maybe the Navy's radar has improved since my time.


If that sailboat didn't show up on radar, it wasn't turned on. However, the
"Mark I" eyeball should have been working well, considering all the people on
"lookout" aboard a USN ship running the channel.