I read in Practical Sailor about radar, and their reccomendations were
the Furuno 1715 (? I think), and not rated as good was the 1623. I
have a race boat, and want a radar, but as small and light as possible.
While sailing aboard Derek Baylis, a Wylie Cat 65 this past weekend, I
asked the captain what he thought of the 1623, since that is what was
on board. He answered that it was the worst piece of junk for a radar
he's ever seen, and he has much experience. Here I was ready to buy
one, but now not so sure about the 1623.

A few questions. Is there another small radar that is good? Is the
quality of the radar directly related to the size of the radome? What
are the pros and cons of locating a radar on short mast aft, as many
cruisers have, or on the main mast of a sloop?

thanks for any help,

Luc

There is a review on radars in practical sailor recently. Their high
pick was the furuno 1725(?) I had it a liked it.

Bob

Charlie Morgan wrote:
On 7 Nov 2006 10:29:11 -0800, "luc" wrote:

I read in Practical Sailor about radar, and their reccomendations were
the Furuno 1715 (? I think), and not rated as good was the 1623. I
have a race boat, and want a radar, but as small and light as possible.
While sailing aboard Derek Baylis, a Wylie Cat 65 this past weekend, I
asked the captain what he thought of the 1623, since that is what was
on board. He answered that it was the worst piece of junk for a radar
he's ever seen, and he has much experience. Here I was ready to buy
one, but now not so sure about the 1623.

A few questions. Is there another small radar that is good? Is the
quality of the radar directly related to the size of the radome? What
are the pros and cons of locating a radar on short mast aft, as many
cruisers have, or on the main mast of a sloop?

thanks for any help,

Luc

The 1623 is a very good quality, but small and basic, RADAR. It would
help to know precisely why that captain didn't like it. He may be
comparing it to very large, open array equipped commercial boat RADAR.
No smaller RADAR with a covered array is going to compete with that.
That doesn't make the smaller units junk, though.

What kind of situations do you encounter that RADAR seems like it
would be helpful. Do you cruise as well as race? What sort of areas as
far as traffic, and general conditions?

CWM

luc wrote:
I read in Practical Sailor about radar, and their reccomendations were
the Furuno 1715 (? I think), and not rated as good was the 1623. I
have a race boat, and want a radar, but as small and light as possible.
While sailing aboard Derek Baylis, a Wylie Cat 65 this past weekend, I
asked the captain what he thought of the 1623, since that is what was
on board. He answered that it was the worst piece of junk for a radar
he's ever seen, and he has much experience. Here I was ready to buy
one, but now not so sure about the 1623.

A few questions. Is there another small radar that is good? Is the
quality of the radar directly related to the size of the radome? What
are the pros and cons of locating a radar on short mast aft, as many
cruisers have, or on the main mast of a sloop?

thanks for any help,

Luc

Hi Luc,

The size of the radar antenna is very much related to the ability to get
good "resolution". There are many different examples, here are a couple:
A small gap looks like straight land line (until you get very close),
Two nearby boats or objects looks like one single boat. Objects apear
bigger than they are.

There is a value in the specs that you can search for. Its called
Horizontal Beamwidth in english. The bigger the antenna the higher the
liklyhood that this value is small. The smaller the value the less
extended objects will appear on the screen - the better the resolution.

You will probably find radomes with values between 3 and 7 degrees. You
dont need to bother too much about the vertical beamwidth. Its usally
arround 20+ degrees. Watch out if it gets much lower since you might
then have difficulties getting a good reading in a small boat during
high sea.

Garmin GMR21 radome horizontal beamwidth = 3,6 degrees.
Garmin GMR404 open array horizontal beamwidth = 1,1 degrees.

I would of course like to have the 1,1 degrees but it would come at a
very high cost and a very bulky antenna. One that you can hit your head
on when it spins (yes this happens more often than one would think) and
wouldnt work well on most sail boats.

there are of course other aspects as well. How well they push back the
side lobes and how fast the pulse rate can be and that the pulse rate
changes with the range setting. Oh yeah, how fast they rotate. The
faster you go on the water the faster you want the radar to spin, since
this affects how fast your screen image will upate. Low-end radars
update once ever two seconds (it actually updates all the time but it
takes two seconds for the radar to update the whole image from 0 - 360
degrees).

Automatic tune, gain, rain clutter and sea clutter can be good but
people who dont like to rely on this probably want solid knobs they can
use to change these values, not having to dig arround in menus.

The "worst" radar I have tried was some sort of no-name radar with black
and white lcd screen and probabaly a horizontal beamwidth of 7 degrees.
The shorest range was 0.250nm. But it still worked great and did the job
in the fog! Its sooo much better than no radar at all

I dont know if you will be using the radar in-doors or out-doors. Maybe
that will affect the type of screen you go for. Night time there's no
problem with sunlight that would normaly cause a problem for LCD's. But
I dont really know because all the LCD's I've used was indoors.

Regards
david

luc wrote: " I have a race boat, and want a radar, but as small and
light as possible"

Luc,

Your concerns/focus are misdirected if your going to focus on small and
light. With a race boat, if your going to do it at all, you should make
it (a) worth doing, e.g. insure your going to get performance you can
use and in doing so consider a 4kw unit (better to see other sailboats
most of which have an unbelieably weak radar return) and a color
chartplotter (radar overlays gps map) to make it more probable you can
make use of the image (b) focus on insuring the radar unit dosn't foul
the sails or add to much weight aloft, e.g. consider mounting the radar
on a pole (adds even more weight) off the stern or mount off the
backstay or if on the mast put a ring around it so your sails or
halyards wont get caught on it, and (c) realize that the weight of the
radome is really inconsequential compared to the mounting hardware and
chartplotter, and inconsequential compared to distorting your wind
instrument results in light air or choppy seas if you mount it high up
in your mast (at a minimum it needs to be a couple of feet above your
boom, so your boom dosn't get caught in the radar return)

My next radar is going to be 4kw, because I am just amazed how my 2kw
can get a strong return from a childs mylar baloon sitting on the
surface of the sea, and is entirely blind to 40 foot and smaller
sailboats, as well as many motor boats.

One thing I am glad I did with my radar, is put it on a self leveling
mount, so I can use it under sail.

Dan





luc wrote:
I read in Practical Sailor about radar, and their reccomendations were
the Furuno 1715 (? I think), and not rated as good was the 1623. I
have a race boat, and want a radar, but as small and light as possible.
While sailing aboard Derek Baylis, a Wylie Cat 65 this past weekend, I
asked the captain what he thought of the 1623, since that is what was
on board. He answered that it was the worst piece of junk for a radar
he's ever seen, and he has much experience. Here I was ready to buy
one, but now not so sure about the 1623.

A few questions. Is there another small radar that is good? Is the
quality of the radar directly related to the size of the radome? What
are the pros and cons of locating a radar on short mast aft, as many
cruisers have, or on the main mast of a sloop?

thanks for any help,

Luc

"luc" wrote in news:1162924151.581326.150280
@m7g2000cwm.googlegroups.com:

A few questions. Is there another small radar that is good?

You get what you pay for. It's that simple. More power has more
range..IF it's up high. It can't see over the horizon. Its horizon is
the same as yours on a clear day. The difference is it can see through
fog and in the dark. The stronger its transmitter, the stronger its
returns from the targets and the strong transmitter making stronger
returns can see more at the same distance in bad weather. Read that,
smaller targets, too.

Is the
quality of the radar directly related to the size of the radome?

The larger the antenna array, the narrower its beamwidth (horizontally).
The narrower the beamwidth, the better it is at resolving the target's
position. A wider beam makes an arc of a target on the display, from
angle it starts seeing the target to the angle it loses the signal from
the target. A bigger antenna, with a much narrower beamwidth, cause a
smaller target on the display, raising the accuracy of the bearing of the
target. The narrower beamwidth also turns one wide target on Radar A
into 4 distinct targets from the big antenna on Radar B. B simply
resolves the targets as individuals because the beam is narrow enough to
stop receiving one target before starting to receive the next as it
sweeps by. So, instead of a blob, you get 4 dots showing better
positions. It's all about horizontal beamwidth. We want narrow
horizontal beamwidth but WIDE vertical beamwidth. If the vertical
beamwidth is too narrow, when your boat heels over or pitches and rolls,
none of the beam that's so narrow lights up the target, so no signal
returns and he doesn't show up on the screen. These tilting mounts sound
nice and do, slightly, improve target painting, but the radars' vertical
beamwidth is so wide, by design, you'll see the target out the beams
heeled over 35 degrees, anyways. The tilting mount centers the RANGE of
the allowable vertical tilt it will tolerate.

What
are the pros and cons of locating a radar on short mast aft, as many
cruisers have, or on the main mast of a sloop?


That's easy. Climb up to where you think you're going to put the radar
while drifting in the harbor. How far can you see? That's how far the
radar can see. It sees targets over the horizon that are tall enough to
come up above the horizon, like tall TV towers, big buildings, water
towers, lighthouses. If you can't see it, the radar can't, either, no
matter what its antenna size and power. It's not magic or clairvoyant.

There's another problem. As you raise up the antenna higher and higher
to see that ship 32 miles away, the vertical beamwidth ends at a higher
and higher altitude, farther and farther from the boat CLOSE IN. From
the top of the mast, that big bouy you're about to run into disappears
from the screen in the fog because the bottom of the radome is a radar
shield to keep from cooking the kids' brains on deck. So, the higher the
radar is located, the further out from the boat the close in targets
disappear because you're shooting the signal right over the top of them.
In a sailboat, I don't get too excited seeing a target over 6 miles away
unless it's doing over 100 miles per hour. What I get excited about is
seeing that damned Bouy in the middle where the two channels intersect in
the fog....you know....so I don't run over it and scrape up the gelcoat,
looking like a complete fool...(c; I always thought it unfortunate
someone doesn't make a sector scanning radar to mount on the bow that can
see only 1000 yards in an arc of 120 degrees, straight ahead. It would
have a very short pulse length, which is the other limit on how close the
radar can see the target from the boat. Radar travels at 300 meters per
microsecond. During the time the transmitter is transmitting, the
receiver is shorted out to protect its sensitive receiver
electronics...on every pulse, we hope. If the transmitter is on for 1
microsecond, any target's echo less than 150 meters away (out, reflect,
come back), comes back while the transmitter is on and the receiver is
off. So, no target is received. If the pulse width (transmitter on
time) is .1 microseconds, the distance is 15 meters and way too late to
turn...(c; Modern radars adjust their pulse widths and the number of
pulses per second (repetition rate) as you reduce range, because close
targets don't need so much RF power so wide to see them with the display
set so close. (Your sonar also works this way, but at sound speed in
water, lots slower.) The pulse width also determines how much resolution
your radar sees on targets close together in line with your signal. If
two boats are in line with your sight and 100 meters apart, the wide
pulsewidth shows one thick target. Narrow pulsewidths resolve them as
two targets because the signal that bounces back shuts down from the
close target before the signal from the outer target starts, leaving a
gap in signals, and a resulting gap in display blip.

In a slow sailboat, compared to something going 30+ knots draining the
tanks, I think 25 ft up is a good compromise between range out 6 miles
and range close in on that nasty bouy with the gelcoat cutting
barnacles....(shudder)

Of course, once the proper short transmitter is beaconing all the bouys
and obstructions, and the boats are forced to either beacon their AIS
data or stay at the dock, all this becomes moot....Watch this:
http://www.aisliverpool.org.uk/currentmap.php?map=48
Just move your mouse pointer over any ship in the Irish Sea and look at
what AIS is all about. Radar's obsolete...It's time America joined the
21st Century. If you can afford to go to sea, you can afford an AIS
transponder, which will get cheaper and cheaper if the market were
expanded rapidly.



Larry
3rd mate engineering, S/V "Lionheart"....
A boat can never have too many electronic gadgets....(c;

One point Larry missed: That big array will focus the transmit power available.
So 4 KW with a small array will get the same range as 2KW with a small array.

Right Larry?

Also: even in typical power boat, how often do you care about traffic more than
a mile a or two away? I'd rather have really good results close in and NOTHING
more than a couple of miles away (I do boat in an area where there's very little BIG
boat traffic. Maybe a dozen cruise ships a year, and they come in after my boat's
on the trailer on the way home, and leave while I'm diving.


"Larry" wrote in message ...
"luc" wrote in news:1162924151.581326.150280
@m7g2000cwm.googlegroups.com:

A few questions. Is there another small radar that is good?

You get what you pay for. It's that simple. More power has more
range..IF it's up high. It can't see over the horizon. Its horizon is
the same as yours on a clear day. The difference is it can see through
fog and in the dark. The stronger its transmitter, the stronger its
returns from the targets and the strong transmitter making stronger
returns can see more at the same distance in bad weather. Read that,
smaller targets, too.

Is the
quality of the radar directly related to the size of the radome?

The larger the antenna array, the narrower its beamwidth (horizontally).
The narrower the beamwidth, the better it is at resolving the target's
position. A wider beam makes an arc of a target on the display, from
angle it starts seeing the target to the angle it loses the signal from
the target. A bigger antenna, with a much narrower beamwidth, cause a
smaller target on the display, raising the accuracy of the bearing of the
target. The narrower beamwidth also turns one wide target on Radar A
into 4 distinct targets from the big antenna on Radar B. B simply
resolves the targets as individuals because the beam is narrow enough to
stop receiving one target before starting to receive the next as it
sweeps by. So, instead of a blob, you get 4 dots showing better
positions. It's all about horizontal beamwidth. We want narrow
horizontal beamwidth but WIDE vertical beamwidth. If the vertical
beamwidth is too narrow, when your boat heels over or pitches and rolls,
none of the beam that's so narrow lights up the target, so no signal
returns and he doesn't show up on the screen. These tilting mounts sound
nice and do, slightly, improve target painting, but the radars' vertical
beamwidth is so wide, by design, you'll see the target out the beams
heeled over 35 degrees, anyways. The tilting mount centers the RANGE of
the allowable vertical tilt it will tolerate.

What
are the pros and cons of locating a radar on short mast aft, as many
cruisers have, or on the main mast of a sloop?


That's easy. Climb up to where you think you're going to put the radar
while drifting in the harbor. How far can you see? That's how far the
radar can see. It sees targets over the horizon that are tall enough to
come up above the horizon, like tall TV towers, big buildings, water
towers, lighthouses. If you can't see it, the radar can't, either, no
matter what its antenna size and power. It's not magic or clairvoyant.

There's another problem. As you raise up the antenna higher and higher
to see that ship 32 miles away, the vertical beamwidth ends at a higher
and higher altitude, farther and farther from the boat CLOSE IN. From
the top of the mast, that big bouy you're about to run into disappears
from the screen in the fog because the bottom of the radome is a radar
shield to keep from cooking the kids' brains on deck. So, the higher the
radar is located, the further out from the boat the close in targets
disappear because you're shooting the signal right over the top of them.
In a sailboat, I don't get too excited seeing a target over 6 miles away
unless it's doing over 100 miles per hour. What I get excited about is
seeing that damned Bouy in the middle where the two channels intersect in
the fog....you know....so I don't run over it and scrape up the gelcoat,
looking like a complete fool...(c; I always thought it unfortunate
someone doesn't make a sector scanning radar to mount on the bow that can
see only 1000 yards in an arc of 120 degrees, straight ahead. It would
have a very short pulse length, which is the other limit on how close the
radar can see the target from the boat. Radar travels at 300 meters per
microsecond. During the time the transmitter is transmitting, the
receiver is shorted out to protect its sensitive receiver
electronics...on every pulse, we hope. If the transmitter is on for 1
microsecond, any target's echo less than 150 meters away (out, reflect,
come back), comes back while the transmitter is on and the receiver is
off. So, no target is received. If the pulse width (transmitter on
time) is .1 microseconds, the distance is 15 meters and way too late to
turn...(c; Modern radars adjust their pulse widths and the number of
pulses per second (repetition rate) as you reduce range, because close
targets don't need so much RF power so wide to see them with the display
set so close. (Your sonar also works this way, but at sound speed in
water, lots slower.) The pulse width also determines how much resolution
your radar sees on targets close together in line with your signal. If
two boats are in line with your sight and 100 meters apart, the wide
pulsewidth shows one thick target. Narrow pulsewidths resolve them as
two targets because the signal that bounces back shuts down from the
close target before the signal from the outer target starts, leaving a
gap in signals, and a resulting gap in display blip.

In a slow sailboat, compared to something going 30+ knots draining the
tanks, I think 25 ft up is a good compromise between range out 6 miles
and range close in on that nasty bouy with the gelcoat cutting
barnacles....(shudder)

Of course, once the proper short transmitter is beaconing all the bouys
and obstructions, and the boats are forced to either beacon their AIS
data or stay at the dock, all this becomes moot....Watch this:
http://www.aisliverpool.org.uk/currentmap.php?map=48
Just move your mouse pointer over any ship in the Irish Sea and look at
what AIS is all about. Radar's obsolete...It's time America joined the
21st Century. If you can afford to go to sea, you can afford an AIS
transponder, which will get cheaper and cheaper if the market were
expanded rapidly.



Larry
3rd mate engineering, S/V "Lionheart"....
A boat can never have too many electronic gadgets....(c;

Luc,
The Furuno radars are as good, if not better than all the others, but the
point you are missing is performance. You have stated that you need a radar.
Here there are two things that outweigh all the others. The first is array
size. Target descrimination is everything. The small scanners spread their
power across a beam width of 3 to 4 degrees. A 6 ft open array has a beam
width of 1.2 to 1.8 degrees. This effectively doubles the power delivered to
a target. The weight difference is only 10 to 15 lbs. Since range is NOT as
important as close in targets mounting the radar aft outside of the sail
plan, extra size and weight is of no consequence. Add to that more power and
you have a radar that truly discriminates one target type from another. So,
the rule is bigger and more powerful is better. If you have the electric
power and the room , use it.
Steve

"luc" wrote in message
ups.com...
I read in Practical Sailor about radar, and their reccomendations were
the Furuno 1715 (? I think), and not rated as good was the 1623. I
have a race boat, and want a radar, but as small and light as possible.
While sailing aboard Derek Baylis, a Wylie Cat 65 this past weekend, I
asked the captain what he thought of the 1623, since that is what was
on board. He answered that it was the worst piece of junk for a radar
he's ever seen, and he has much experience. Here I was ready to buy
one, but now not so sure about the 1623.

A few questions. Is there another small radar that is good? Is the
quality of the radar directly related to the size of the radome? What
are the pros and cons of locating a radar on short mast aft, as many
cruisers have, or on the main mast of a sloop?

thanks for any help,

Luc

Note: My earlier recommendations (4kw, stern mounting, etc.), take into
account you have a racing boat, are around other racing boats, and if
your are really compelled to add a radar at all, focus on features that
will make it worth doing and features that are more important in
minimizing the impact on racing ( than the weight of the radome ) in
planning your total purchase and installation, rather than for example
range. Even if you could save 5 pounds off the typical 18 lb weight of
a radome, it wouldn't necessarily improve performance since the weight
of the entire system (assuming no additional batteries are needed) will
be north of 50 lbs, and the 5 lbs especially won't matter as your deck
crew is dealing with a halyard or sail getting caught in it even for a
few seconds.

Also ... in case you started doing the math of how much power you will
need and possible upgrades of your electrical system, and are
attempting to convert that 2kw or 4kw into amp hour draw on your
battery, hold up.

Also ... note that 4kw radomes such as Raymarine's only use 38 watts of
battery power while active, and 10 watts in standby. The transmitter is
in the "off" cycle of each pulse, for most of each second. Since all
the electronics in the radome are on all the entire time, the
chartplotter of course is on all the time, the total power consumption
between a 2kw and 4kw system is negligable.

Also ... in case you started doing the math of how much power you will
need and possible upgrades of your electrical system, and are
attempting to convert that 2kw or 4kw into amp hour draw on your
battery, hold up.

A 4kw radomes such as Raymarine's only uses 38 watts of battery power
while active, and 10 watts in standby (per the documentation). That is
a lot less than the 4000 watts you might be thinking 4kw implies. The
transmitter is in the "off" cycle of each pulse, for most of each
second, giving the electronics some type to store up those 38 watts and
release them in a powerful pulse. Since all the electronics in the
radome are on all the entire time, the chartplotter of course is on all
the time, the total power consumption between a 2kw and 4kw system is
negligable.

Dan