New Radar

M

mcc272

New member
For those contemplating adding radar or upgrading their radar, there is a new radar in the process of being introduced that looks positively amazing. It is broad band radar. I first read about it on Panbo at the following link:
http://www.panbo.com/archives/2008/11/n ... _deal.html

Lowrance, Simrad and Northstar are the Navico brands that will have it when it starts to ship in the next couple of months. The scanner transmits at 1/2000 the power of a typical radar. This has 2 very important benefits -- electrical draw is dramatically reduced and secondly, the radiation from the scanner, which can have serious health impacts, particularly on the eyes if you get in the beam, is limited. Lowrance says it "emits 10 times less energy than an average cell phone." The unit is instant on rather than a 3 minute warm up like a typical radar. Finally, target separation at close range is just amazing as there is no "main bang" at the center of the screen like a pulse band radar. The closest range is 1/32 mi rather than 1/8 mile and based on the video, you could easily navigate in closely packed mooring field in dense fog. It is worth checking out www.lowrance.com and following Panbo for additional details as they come available. Note that this is "broadband radar" not the "high definition digital radar" that Lowrance offers.

Coupled with the new HDS chartplotters from Lowrance which have super screens and which come up to 10" screen size, an ideal size for our boats, these units are pretty exciting. Exciting enough to get me, a dedicated Furuno guy who just came from a boat with 2 Furuno radars and who was planning to put a 4kw NavNet 3D unit on his CD22 to take a big step back and figure that this new broadband radar from Lowrance with a 10" Lowrance HDS unit might be a far better solution.
 
Certainly a product which bears watching. I have Lowrance products and have had excellent service. Some have had problems with technical help (See The Hull Truth Electronics forums).

My experience is that warm up time is 60 to 90 seconds in most smaller radars. The radiation hazard is only at very short distances--and not off the center axis of the beam.

The videos are impressive--and I am sure that Furuno and RayMarine will also have comparable units shortly. The one thing which does not change with the broad band radar is the descrimination--that is the ability to separate two images at a distance. This still depends on the size of the scanner (beam width being smaller, gives a better separation).

This is an illustration of what I refered to a month or so ago on exciting times in marine electronics--and there are more to come.
 
I wouldn't panic if one had a regular old fashioned 2 Kw radar. If this new radar transmits at 1/2000 the power of a 2 Kw radar, does that mean it transmits at 1 Watt? That would be an increase in sensitivity of 2000 or 33 dB. With no apparent increase in the antenna size, that's startling.

By the way, that 1 watt is total power going out in the radar pulse, not average transmitting power, if that's what they mean. Since everyone else uses a minimum of 2000 watts (2 Kw,) that's a unique development.

Also, could someone clarify what broadband radar is? The radar with which I'm familiar transmits at a single frequency, which is swept to produce the chirp. If you go broadband (i.e., a wider frequency spread,) you're spreading the transmitted energy out over a wider spectrum, and you have to have a wide band receiver to collect it all. I wouldn't think that would give the best discrimination.

I'm confused.

Boris
 
Navco describes the "Broad band" as thus:

"Navico Broadband Radar sends a continuous transmission wave with linear increasing frequency (hence the term Broadband).
The wave retains its frequency as it travels out and reflects back from any objects. Meanwhile, the transmitter continues to output an increasing frequency. The difference between the currently transmitted and received frequencies, coupled with the known rate of frequency increase, is the basis for precisely calculating a “time of flight” and target distance. Since FMCW constantly builds up radar return energy
(vs. a single pulse), this system provides target detection superior to pulse radars while transmitting at far lower energy levels."

There is a good discussion of power of the magnitron vs the SS devices and differences in the discussion section at the link which Jim refered to:


http://www.panbo.com/archives/2008/11/navico_broadband_radar_a_really_big_deal.html

Basically it is an old ineffecient magnatron, vs the new solid state transmitter, different waveforms, and much shorter pulse duration which give the same "power" as a unit which uses considerably more current. But these new broad band units may not be as good at 24 miles. I rarely run my radar at more than 6 miles and more frequently at 3 miles. The 1/32 mile range certainly has an advantage going into a crowded anchorage during low visability.
 
I don't generally run my radar on longer ranges than 3 miles. Frequently, I am at 1 mile and less in crowded areas such as harbors. I do use the long ranges to detect thiunderstorms and to plot their movement and it will be interesting to see how the broadband units will work for that. My home waters are sufficiently crowded, even in low visibility conditions, that longer ranges are not useful as it looks like the screen has developed a case of the measles. I would feel differently if I was cruising offshore or passagemaking where there was less traffic. The only time I ever relied on 12 mile range to identify targets was when we had the Indian (feather, not dot in the words of one of my Indian (dot, not feather) friends)) which ran up and down LI Sound at nearly 50kt. I could identify them at 12 miles as they were the only thing at that range that visibly moved. We run on radar 100% of the time and that way, running at night or in reduced visibility is not a big deal as we have so much experience adjusting our radar and interpreting the results. Radar is very much a technology where paractice makes perfect or at least lets you get a whole lot closer to perfection.

Jim
 
Thanks, Bob

My understanding of why they only send out pulses is so that the receiver will not receive the transmitted signal, until it returns as an echo so there's no spillover from the the transmitter directly to the receiver. (I'm sure that there's a better way of stating this.) So they gate the receiver ON for the expected time of flight. However, one can correlate signals over time. This is done in synthetic aperture radar (SAR), for example, but they're consecutive pulses. I'm going to have to try and find out how this Navico radar differs from the ones I've used, and it'll be interesting.

Remember their technique gives them a 33 dB gain over a standard receiver. That's what so impressive. By the way, my comments reflect my unfamiliarity with broadband radar, not my disbelief.

Boris
 
For those interested parties, here's a presentation of Navico's radar: Navico Presentation It's a PDF file, describing the operation. They do use a chirp, which is a swept frequency pulse. Also they use SS devices instead of magnetrons. Magnetrons aren't vacuum tubes, but metal cavities used to create microwaves, and in the JRC on Journey On are driven by transistors. However, Navionics does their scanning with 0.1 watt. I'm impressed.

They also recommend this radar as a short range radar, perhaps as an augmentation to a 2-4 Kw radar. The range results given in the presentation don't go out over 1/16 mile.

Boris
 
journey on":jvrhjisc said:
For those interested parties, here's a presentation of Navico's radar: Navico Presentation It's a PDF file, describing the operation. They do use a chirp, which is a swept frequency pulse. Also they use SS devices instead of magnetrons. Magnetrons aren't vacuum tubes, but metal cavities used to create microwaves, and in the JRC on Journey On are driven by transistors. However, Navionics does their scanning with 0.1 watt. I'm impressed.

They also recommend this radar as a short range radar, perhaps as an augmentation to a 2-4 Kw radar. The range results given in the presentation don't go out over 1/16 mile.

Boris
Click to expand...

On their specifications for the unit they claim a range of 24nm - same as other radars and limited mostly by the earth's curvature at that range.
 
I think I'll keep my Furuno and when these become available, upgrade my Lowrance to the latest (depending on price)

Sea clutter and rain are only briefly mentioned--and it will be very interesting to see how well they are filtered out. Also in one of the slides (thanks Boris for the link)--the pilings are shown as elongated echos--this is understandable, but may be confusing, since "anchored boats" are shown as dots.

Also it appears as if this type of radar does not need tuning--whereas the conventional magnitron type often performs much better if tweeked by the operator than by the "auto" function.

I never found that radar current draw was a problem on any of my boats, even sailing across oceans.

It will be interesting to see what the price is--theoretically this could be made cheaper than conventional radar.
 
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