I have checked the internet repeatedly and can find no information about
using small boat radars. It is the most complex device with the least
information about its' use we can buy for a boat. Does any body know where
i can get 'tips' and suggestions for using radar safely and effectively?
The manufacturer Si-tex/Nobeltec don't have anything beyond the most basic
how to turn on and make minor adjustments.
New guy

On Sat, 06 Sep 2003 02:17:49 GMT, new guy wrote:

I have checked the internet repeatedly and can find no information about
using small boat radars. It is the most complex device with the least
information about its' use we can buy for a boat. Does any body know where
i can get 'tips' and suggestions for using radar safely and effectively?
The manufacturer Si-tex/Nobeltec don't have anything beyond the most basic
how to turn on and make minor adjustments.
New guy

When you turn your radar on, there will be a long delay while we wait
for the magnetron transmitter tube up in the radome to warm up and
stabilize. The display will warn you of the warmup and will tell you
when you can turn the transmitter on......

Boat radar isn't really that complicated. It transmits a pulse. From
the time the transmitter shuts down, a few microseconds after it
starts (It's called Pulse Width), the receiver starts listening for
the transmitter's signal to bounce off something.....something that
MUST reflect radio waves....which isn't wood, fiberglass or anything
else non-conductive to electricity.

The modern receiver is a computer, not a direct-displaying analog
device like you see in an old movie. Analog or digital, it all works
on the speed of light....a defined speed of radio waves.

You really don't need more information to make it work. Your boat is
at the center of the display, the center of the sweeping cursor that
going around exactly the same speed and direction as your antenna.
The radar only sees what's in front of the antenna, painting targets
on each sweep. The size of the blob of target depends on how big the
target is, how narrow the antenna's beamwidth horizontally
is....you'll soon recognize the size of the ships from the display by
comparing them on a day you can see them.

The computer sets the length of time it leaves a target on the screen,
these days, not how long we can keep the phosphor of the old CRT lit
up with just one blast like WW2. Your new computerized display is also
capable of making a "trail" of returns it has seen on moving targets
and the better ones display where the computer projects the target
will be using its current course and speed into the future.

All you really need do is turn it on. The computer will adjust the
controls for you, once you tell it how to display the picture.......

Headings - the choices......

For a new user of radar, I always recommend the display be set to
course up. This makes the display the same as what you see looking up
from the helm. It's easier to visualize and any obstructions you need
to avoid are "ahead" of you coming at you, in the center of the screen
from the top of the screen, no matter where the boat is actually
pointing. Targets to port are on the port side of you in the center.
Targets to starboard are on the starboard side of you in the center.

If you have a stand-alone radar with no GPS or compass heading input
to it, that's the only display it will have....bow pointed up......

If your radar's computer has input from a GPS receiver and/or a
compass sensor, you get more below....

You can also tell the computer you wish to make the display North Up,
where the top of the screen is North, no matter what your boat's
course is. You can also set the display to Course Up, so the top of
the display is always pointed at the next waypoint, even if you are
heading off in another direction. Each has its uses.....

RANGE - RADAR means RADio Detection And Ranging. You are at the
center of the display looking out to the "radio horizon", whos
distance depends on how high your radar antenna is. The radio horizon
is a little farther than your visual horizon if you were sitting on
the radar antenna's platform. This is NOT dependent on how POWERFUL a
transmitter you have. Power IS our friend when we want to see targets
with tiny radar cross sections. So isn't repetition rate, but yours
is fixed so you're stuck with it.

Range shows up on your radar display as the distance away from the
center of the screen where the sweep starts....exactly as it does if
you're standing on the deck looking around towards the horizon. The
further away from the center of the display a target is, the further
away from your boat it is.....very simple.

Range Calibration - There are, basically, 2 ways to tell how far a
target is. Simplest is Range Rings. The computer will display a set
of circular rings at intervals of 1/8, 1/4, 1/2, 1, 2, 4, 8, 16 miles
from the center of the display so you can kind of eyeball how far a
target is without doing anything to the display. The display is
linear in RANGE.

The Cursor - To get a more exact BEARING and RANGE to a target, the
computer provides a cursor and does all the triangulation calculations
for you, on the fly, as you move the cursor around with the arrow keys
on the display. Press and hold the arrow key and the cursor keeps
moving. Joysticks and trackballs are for rich people. Po' folks use
arrow buttons. Use is quite simple. Put the cursor over the target
blob and read the bearing and range off the edge of the display or a
little window on it. Old radars had mechanical range counters like
the odometer in a 1957 Chevy on a rotating knob that controlled the
cursor distance from the center. Another knob turned the cursor line
in azimuth and was calibrated in bearing, somehow. Aren't computers
great?!

So, now we know where the target is and how far way he is........let's
track him.......

The more sophisticated boat radars have some kind of automatic target
acquisition and ranging where the computer will automatically "keep an
eye" on your favorite targets for you. Raymarine calls it MARPA.
Raytheon loves acronyms because they still work for the military who
love acronyms. Marpa, or whatever your company calls theirs, is
pretty easy to use. You point the cursor at a target and press the
MARPA button. The computer notices the target and puts a little box
on the screen appropriately labeled. From this point on until you
cancel the target or it simply disappears out of range, the computer
will move the MARPA cursor for you, watch you course and his course
and raise hell if they look like they're going to collide or get
within X nm of each other set by a parameter you've defined. Our
SL70CRC Plus will track 10 targets simultaneously. In the "Old Navy",
this took a compartment full of huge computers. Today it's one IC and
draws so little power it doesn't even get warm running continuously.
Dispite the 2nd Amendment, the government won't let us have an
NMEA-directed missile launcher to assign to MARPA targets.

ALARMS - Wake me up if something doesn't look right.......

Your modern boat radar has several alarms you can set......

Intrusion Alarm - You define your little piece of seawater as a wedge
from your boat out X miles from here to here in azimuth from the boat.
The imaginary wedge you've created in the computer's mind follows the
boat as it runs. If any object enters the boundaries of the wedge
THAT GIVES A RADAR RETURN, the computer sets off an alarm to let you
know. The important part is THAT GIVES A RADAR RETURN. Case in point
was on a trip up from Daytona Beach last year. I had the radar watch
setup to 3 miles and about 60 degrees on either side of our course
while we were eating breakfast in the cockpit of an Endeavour 35
sloop, calm seas, following wind about 12 knots....easy sailing. I
looked up from my eggs and grits and a HUGE WOODEN CABLE REEL AS BIG
AS A HOUSE floated by about 50 yards from the beam! No alarm??
What's dis?? I rushed around to look at the display as the reel went
aft of us....THE RADAR SAW NOTHING FROM 50' AWAY TO THE HORIZON
AFT....

Radars only see REFLECTIVE targets.....which don't included empty
wooden cable reels.....dammit. I still shudder to think what would
have happened to us if we'd rammed that thing at 8 knots at 3AM with
no moon. It's something to ponder, keeping you awake in the V
berth....

Radars cannot replace the human watch.....

That's basically "it". Ask us questions, now. What kind of radar
does your boat have, might be a good answer first. Someone on here
has your specific make/model. I'll be glad to help with the
operational stuff on the Raymarines I have hundreds of hours staring
bloodshot eyes at all night.


Larry

Extremely intelligent life must exist in the universe.
You can tell because they never tried to contact us.

There are videos available from most radar mfg. I've seen them at West Moron
and I think most store have a rental arrangement..

I had one for my Furuno 1721 and it was good, with all the basic info you
need to use the unit effectively.

There is also Starpath Radar Trainer. It is a computer software program that
allows you to learn various radar navigation on your computer. I have an old
DOS version that is still very good. I suspect the Window version should be
even better. It is also available for the Mac.


--
My opinion and experience. FWIW

Steve
s/v Good Intentions

"new guy" wrote in message
...
I have checked the internet repeatedly and can find no information about
using small boat radars. It is the most complex device with the least
information about its' use we can buy for a boat. Does any body know where
i can get 'tips' and suggestions for using radar safely and effectively?
The manufacturer Si-tex/Nobeltec don't have anything beyond the most basic
how to turn on and make minor adjustments.
New guy

For a few weeks use it in daylight and good visibility. Then you will have
an idea of what it can see, and what it can't, when the visibility is bad.

Larry,

Any bugs with your Ray MARPA or does it generally work as advertised? Can it
track targets when your boat is slewing in azimuth like in a big following sea?


Considering upgrading radar to a MARPA capable one and am trying to decide
which one really works well. Had differing reports including one that said his
worked poorly until he upgraded his heading reference to a KVH Gyro Trac. The
pure fluxgate heading sensor didnt do well.

Any info appreciated.

My suggestion is to leave the radar on constantly in the learning phase. On a
clear day you can learn a LOT by comparing what you see (and don't see) on the
radar compared to eyeballing the scene. I still marvel at how well (low flying)
Pelicans show up. I'd have thought they were the ideal stealth plane. What
reflects so well?

On 06 Sep 2003 18:54:20 GMT, (BOEING377) wrote:

My suggestion is to leave the radar on constantly in the learning phase. On a
clear day you can learn a LOT by comparing what you see (and don't see) on the
radar compared to eyeballing the scene. I still marvel at how well (low flying)
Pelicans show up. I'd have thought they were the ideal stealth plane. What
reflects so well?


Hmm....I never saw a pelican swallow a radar reflector ball....(c;


Larry

Extremely intelligent life must exist in the universe.
You can tell because they never tried to contact us.

"Larry W4CSC" wrote in message
...
On Sat, 06 Sep 2003 02:17:49 GMT, new guy wrote:

It's easier to visualize and any obstructions you need
to avoid are "ahead" of you coming at you, in the center of the screen
from the top of the screen, no matter where the boat is actually
pointing.

Targets behind and to the side may well be threats, especially in a
slow-moving sailing vessel. You need to watch the progress of a target
(either electronically or by some plotting method), if it stays on a
constant relative bearing - ie runs down a line from the centre of the
display to its first detection point, then it will hit you. Many sets
without MARPA allow you to put an electronic bearing line (EBL) on 1 or more
targets to monitor this. Of course this also applies to rocks; 'will I
clear that headland ?' is really the same question as 'will that ship hit me
?'

That's basically "it".

I would add that radar can be a great navigation tool. It gives a very
accurate range (less accurate bearing) which allows you to identify features
on land and produce an instant fix by drawing circles on the chart with
centres on the features and radius their distance off. The same procedure
will allow you to confirm the identity of a doubtful feature given a known
position or known features. You can also set up an electronic range ring in
advance of a tricky bit of pilotage and use it to stay a known distance off
land. Just remember that the return from a bit of land does not neccesarily
come from the point where the colour changes on the chart; at a long range
you may be seeing high ground miles inland. At closer range it may depend on
tidal height.

A responsible navigator uses every piece of information at his disposal.

Steve

My Raymarine MARPA works well. It's pretty fun to play with when you're in
the ICW and there are a lot of shrimp boats right offshore. Target about six
of them and watch their predicted tracks.

--


Keith
__
"When I die, I want to die like my grandfather who
died peacefully in his sleep. Not screaming like all the
passengers in his car." - Will Rogers
"BOEING377" wrote in message
...
Larry,

Any bugs with your Ray MARPA or does it generally work as advertised? Can
it
track targets when your boat is slewing in azimuth like in a big following
sea?


Considering upgrading radar to a MARPA capable one and am trying to decide
which one really works well. Had differing reports including one that said
his
worked poorly until he upgraded his heading reference to a KVH Gyro Trac.
The
pure fluxgate heading sensor didnt do well.

Any info appreciated.

Hey, don't laugh. I tracked something one day that had to be either a bird
or a UFO. Although I'd have preferred to see the latter, I have to believe
it was a bird.

--


Keith
__
Did you ever walk into a room and forget why you walked in? I think that's
how dogs spend their lives.
"Larry W4CSC" wrote in message
...
On 06 Sep 2003 18:54:20 GMT, (BOEING377) wrote:

My suggestion is to leave the radar on constantly in the learning phase.
On a
clear day you can learn a LOT by comparing what you see (and don't see)
on the
radar compared to eyeballing the scene. I still marvel at how well (low
flying)
Pelicans show up. I'd have thought they were the ideal stealth plane.
What
reflects so well?


Hmm....I never saw a pelican swallow a radar reflector ball....(c;


Larry

Extremely intelligent life must exist in the universe.
You can tell because they never tried to contact us.