small radar

[ssobol]

Does anyone know if they make a smaller/shorter range radar for small boats. All the one I have seen have antenna heads in the 15-20# range (12-18") and ranges of 24-36 miles.

I don't have a radar, but I would think that for a boat like a C-Dory a radar that has a range of only a few miles (5-10 max) would be plenty. I think that only things within a 1-2 miles is all that I would care about. Anything farther away is not really something that I would worry about. If something does show up within that range, the C-Dory is maneuverable and fast enough to get out of the way.

While you can use a radar only on the shorter ranges if you want, a radar unit that is sized to only reach just few miles might be smaller, lighter, and maybe also less expensive.

A low power radar with an small electronically steered xmit/receive antenna (no moving parts) might be just the thing for smaller boats.

[Sea Wolf]

I'm becoming notable around here for venturing opinions that are sometimes off-base and becoming a victim of hoof-in-mouth disease, but here' another one just for the Christmas Giving Season:

If you can't find a really small radar unit, then none of us can, either.

The newer units are a lot smaller and lighter than the ones of 15-20 or more years ago, thanks to integrated circuits, LCD displays, and other advances, such a improvements in magnetron design, and improved overall electronic efficiency.

Building smaller units than those presently available for retail sales apparently is not economically feasible.

Smaller units would not result in any cost (manufacturing) savings, may compromise quality and performance, and the increased market share for such units would not support their special development, since the existing products cover such a wide range of boating needs.

You might find this article interesting, but it doesn't specifically address the size issue:


Small Radar Systems Explained



On right, Old School Radome courtey Jon C- Lou.

Brought to you by another Boring Day in Rainy Northern California...........

Joe.

[Sunbeam]

I agree that it might be nifty to have a really small/light radome, and close range is the most useful for us most of the time.

OTOH, presuming one is not available (and I don't know of one myself), there are some uses for the 10-20 mile range, even on a C-Dory (usage dependent of course). A couple that come to mind are seeing weather ahead (squalls can show up), or seeing a land mass 15 miles away so you can compare it to your chart and see where you are (say on a larger body of water). In other words, it can be useful for more than just seeing nearby boat traffic.

My guess is that currently, a shorter range radar would just be put in the same outer radome cover anyway, so you wouldn't be gaining much. But one half the size and weight could be cool for some boats. I have not looked but I wonder if something small is made for anglers or kayakers?

Always fun to see what is made for other uses that might be adapted (kayaking, etc.)

[potter water]

Power of the radar does matter to some degree, but a really small radar isn't going to be a mile or two. the signals are extremely high frequency and only have a little power, though it comes in pulses, so not much average current draw when they are running. The dome size has as more to do with the 360 degree coverage of any radar, large or small. Much of the cost of the radar, whether large or small is in the computing and displaying hardware. So not much to be gained if you are expecting "small radar" to have a little bitty dome. I think that a 20 mile range for a boat in the 22 cruiser class is not too far. It is a good thing to see a container ship that far away. If you are seeing it a a couple miles, then you are already going to have to make emergency maneuvers, depending on your relationship to it.

[ssobol]

Of course this is just thinking out loud but, IMO a fair part of the radar unit is the requirement to have a rotating antenna. This is precision made mechanical unit.

Say you had an array of small fixed antennas (maybe dozens) arranged in a ring facing out. You could electronically fire a pulse through each antenna in turn to get what amounts to a sweep. You could fire the antennas sequentially or in some other pattern if necessary and use the unit software to create the radar image. An antenna of this type would do away with the mechanical aspects of the current styles of rotating antennas.

The disadvantage of using a bunch of small antennas vs. a larger rotating antenna is that reduction in the ability to radiate power. This might be countered somewhat by the ability of each antenna to "listen longer" than is possible with a rotating antenna, but due to the propagation speed of the pulse/return pair might not really make much difference. The reduction in the power available for the each pulse would reduce the effective range of this radar.

Solid state electronics and hardware and software logic controls might make it possible to do this.

It was just an idea.

[joefish]

SoBelle, I'm with you. A big honkin' radar system which I would rarely use is not for me. I was heading to Maine and seriously considered it but never made the purchase. The future always moves toward smaller and lighter when it comes to electronics so if we wait/live long enough our wish will come true. For now the best I've seen is this http://fishinggearguru.com/broadbandradar.html

[Sea Wolf]

[Sea Angel]

Joe; DEW Line??
OH, yes. I do remember it and how much older I am now from those days.

As to the question of the RADAR antenna size, I liken it to not the power it can handle(which is a factor), but more to the bearing resolution.

The bearing resolution (antenna transmitted beam width) is how well you can separate a target that is actually two targets at a given range; i.e., are there two boats, or one large one on a given range and bearing. Another example would be to see the separation of a day-mark located at the end of a jetty as you approach it at a right angle to the jetty, or the opening to a river mouth along the coast line.

Note the transmitter 'on and off' cycle will determine the range separation parameters along the sweep bearing line.

I went with the 4KW antenna setup to help with the differentiation with an abundance of small boat traffic in the Lower Chesapeake Bay area.

So, as they say - "Size does matter".

Just my 2 cents worth.
Art

[Foggy]

Short sighted are those who use their small boat radar only for collision avoidance
at close range. Weather avoidance has been mentioned already.

Besides GPS, a compass, local charts and having DR skills, small boat radar is an
excellent navigation aid. Viewing a "lollipop" on a radar screen as a destination
waypoint in fog, heavy seas or at night is more than comforting.

I wouldn't want a small boat radar limited to less than 5 - 10 miles.

Aye.

[Lollygaggin]

If you were lollygagging along at hull speed of about 4 knots and you noticed a cruise ship on a collision course at the 15 mile arc on your radar screen, you would only have about half an hour to react if it was making 20 or so knots. I think 15 mile range could be considered "short" when you think about how fast these large vessels are moving and how un maneuverable they are. Now, suppose it wasn't a cruise ship. Suppose it was a pilot vessel making 35 knots. The 2 mile radar you're talking about would give you about 4 minutes to react if you noticed it right away. IMHO. Hope my numbers are right Good luck with dilemma.

[journey on]

I have a slightly different opinion (of course,) on moders small boat radars. I think that the present small boat radars are darn good and are very compact and small for what they do. Additionally, expecting good data further than the horizon (~8 mi.) is not valid, that data is just a warning.. Below, I'll list some of the items that make today's small radar quite an accomplishment and quite cheap.

A few facts about radar. It works by transmitting an electro-magnetic (e-m) field at some power level, measuring the time of flight to/from a target and combining that time with directional information to give a range picture. The display shows the radar data on a multipurpose screen which is outside of today's radar's. Note that a GPS, for instance just receives data, doesn't transmit anything, especially over miles of ocean.

First, radar is line of sight, so it can only see to the horizon. A radar mounted on top of a C-Dory "sees" about 8 miles to the horizon, no matter at what range the radar is rated. A tall ship or big cliff increases that range, but not by much.

Next, radar uses high frequency e-m power to "see" whats out there. That's 9.3 GHz, about 10 followed by nine zeros.So, however small you make the radome, you need a frequency generator which starts with 13 VDC and ends up with frequencies in the gigahertz range with enough power to travel 24 miles and return. That circuitry is in the radome and takes up volume along with the processing electronics. By the way, the power used by the new Lowrance 3G radars is 165 mw to the antenna which is very very low. That's not 2Kw, but 0.0002 Kw.

Second, for a radar to scan one can point the e-m waves by turning the antenna, having multiple antennas used sequentially, or by bending the e-m field. Remember, we want to have 360 deg of view and have good discrimination of small targets. Better discrimination needs larger antennas. Rotating a single antenna seems the best practical solution, since it gives the largest antenna for good discrimination as well as combining the directional data with the antenna rotation mechanism. For a single antenna, the RF data goes to a single point and doesn't need to be switched. With the 20" dia enclosure (the antenna must be smaller,) the 3G has a resolution of ~5 deg.

And finally, I would suggest lifting a new radome. That 18" cylinder is just there for providing environmental protection to the antenna and support electronics. Remember the radome has to be mounted outside to have a clear FOV. It's mostly empty space, though good to 50 knts of wind. The antenna is a printed circuit board. The electronics is solid-state and integrated, no magnetron. The Lowrance 3G radar weighs 16 lbs, which is light. Small modern radars run ~1200 for HD.

All in all, modern small boat radars are a different world from say 20 years ago. OK, 30 years ago. For the job they do, they're small and cheap and give great performance from 500 ft to 8 miles. More if you're staring at a tanker or cliff, but again that's only a warning. Lowrance advertises that one can see a kayak at 800". I don't know if I believe that, but you certainly can see a bouy at 800' and it's accurate enough to overlay it on a chart.

Boris

[Lollygaggin]

Boris,

Excellent article, thank you. The price of the Lowrance radar is even better than our last purchase; the Furuno 1715 at 15 boat bucks. It was the smallest one that would do the job at the time. The 3G will be going on our next boat,,,,,, if we ever find it.

[Foggy]

['o cino]

DEW line huh? OK, now who remember's Ice Station Zebra? They could've used a short range radar in that application.
I'm all for smaller and more efficient is better, but the 15+ mile range is still desirable...if nothing else, than looking for birds.

[chimoii]

Anyone any experience with the DRS4W from Furuno? I have put off having radar until now and haven't needed it. The cost has put me off getting a 'nice to have' as I would have to spring for a new display as well as the radome. Now along comes Furuno with a $1,700 dome that is able to talk to my iPad. Sounds too good to be true (or the shape of modern technology)??