From: gerard@progress.COM (Gerard Bras)
Newsgroups: rec.boats
Subject: Re: radar
Keywords: Experience with lowcost Radar
Date: 13 Apr 92 22:30:44 GMT
Article-I.D.: progress.1992Apr13.223044.21475
Organization: Progress Software Corp.

jstand@mcnc.org (John K. Standish) writes:

>Very often I find myself navigating at night offshore in the `graveyard
>of the Atlantic', sometimes on purpose but usually the weather drives me
>back to port, with only my Loran/Compass, and extremely limited vision
>spotting the lighted buoys.  The cure is obvious, I need RADAR, and 
>with a 30 ft boat I really don't need a 4-5 Kw open array Furuno.

In my experience radar can be quite useful on a small boat.  It does,
however, have some limitations.  The major thing to understand is that
while radar shows a lot of information it takes some experience to 
be able to interpret it correctly.  In particular, if you expect an
exact image of what you'd see if you weren't socked in you'll
be dissappointed.  It will show you high coastlines in good detail, all 
floating aids will show, and so will a lot of floating hazards like
other boats. What won't show is low rocks, some low coastlines, lobster
pots, floating trash, sandbars, rubber dingys (actually I have pick up
some but not reliably) other hard to spot junk.

One problem with radar is that it tends to show a lot of spurious stuff.
You have to watch it for a minute or so to get a real idea of what's out
there.  Also, targets are not shown in proportion to how well they 
reflect radio waves.  This means a small boat witha a radar reflector
can really light up while another one without the reflector may never
show at all.  So you still have to watch and listen carefully.

On the plus side, radar can be an awesome navigation tool.  When you
know what the target are you can get *very* accurate fixes with it.
I used my radar extensively when I went to Maine last summer.  I don't
know if it saved my life but it was really nice to have on those
foggy days.  Often it made the difference between sailing and hanging
out in the harbor.  WHen you have limited cruising time like us working
folk, this is something to think about.  On the days when I was out in the
fog, nothing ever came close that I didn't spot on radar first, at least
nothing I noticed. :-)

>I would like to know if anyone has experience with the less expensive
>dome style Apelco or Raytheon (< $2000.00)) with 16 - 24 mile range.

I put in a Raytheon R20X last year.  I installed it myself, no problems.
It works beutifully, enough to compensate for lugging that ugly
radome around.  It ran just a little over $2K.

Sailboats present some special problems running radars.  First and fore-
most, small radars have a horizontal plane of around 25 degrees.  This means
that if you are heeled way over you are going to lose "vision" to the 
sides.  There are leveling mounts which can compensate but they cost extra.
The real cadillac model, the Questus, costs almost as much as the radar
itself.

The other sailboat issue is power.  These babies like it!  It's something
like 7 amps when it going so figure this into your battery capacity.

>My biggest concern is the ability to navigate a channel at night and 
>discernabilty of objects (buoys, oncoming vessels, ect) and effect of
>clarity by rain.   

Good radars have filtering which will clear out rain and sea clutter.  DOn't
get one that doesn't have this, though I think all do.  Making channels
is where a radar really shines.  I've maneuvered in harbors where I
already knew the lay of things by radar.  It really works.

>(ie. I'd rather buy a high quality 16 mile range than a poor quality
>24 mile system--- or find out `straight-away' if I am nuts to settle
>for less than the best)

You are only nuts to spend money on a unit that doesn't meet your needs.
The thing you want to look at are in order: angular resolution which is
strictly related to antenna size, display quality, pulse rate varying with
range selection, useful ranges, and output power.  For your needs the
short (<3mi) ranges are the important ones.  This is what swung me to 
the Raytheon units.  In general though I would stay away from the real
cheapies.  The ones I saw had horrid displays.  $2K seemed to me where
I was really starting to get a piece of gear for my money.

Bear in mind that the 16 or 24 mile figure is hypothetical.  Radar is line
of sight.  On normal sailboat installations this amounts to about 10
miles, give or take a few.  The mileage the manufaturer quotes is based
on output power, and more importantly how long the circuitry waits for
the echo.  This is very much related to pulse frequency which is why
you need variable rate.

>Please advise

Please understand that you've asked about a very complex subject.  I'm
by no means an authority.  I looked at a bunch of units, talked to people
who already had radar, bought and installed one, and ran it for six months,
and read some books.  That's the extent of what I know.

One more thing.  My radar listens to my Loran through NMEA0183.  It shows
the LORAN data on the radar screen.  It will translate radials into compass
headings which is a real convenience when orienting the display to a chart.
I would consider this a "must have" on any radar I bought, although I
didn't consider this in my purchase.  It's almost enough to get me to
spring for an electronic compass.

As to specific brands, I'll risk lawsuit and hazard my opinions.  For me it
came down to Raytheon and Furuno.  Icom amde a pretty nice unit but the 
was too big for my nav area, although I think they have a more compact unit
now with the same size screen.  Apelco and all the LCD units were, IMO, not
worth getting.  I did not see the Goldstar units but Coast sells them cheap.
The Raytheon units come with the longest cable, a very expensive part if you
have to buy another.  They also have, by far and away, the best documentation.
It's basically a service manual, complete with part numbers, diagnostic info,
and schematics.  You may not care now but if you need it fixed in some out
of the way place you might.

And another thing.  Regardless of what the salesman tells you, the radar
is very likely to interfere with your LORAN if they are mounted close 
together, like mine are.  Some sheilding took care of this, though.


cheers,
-gb-