Radar or Not ?

[Jim Cate]

G'Day all,

One of the weaknesses of yottie radars (1-4 kw) is that they get blanked out by heavy rain. In general, more power, better performance under these trying conditions. So, I wonder how the broad band technology works in such conditions? Anyone with experience?

Cheers,

Jim

[Dockhead]

PBO just tested a bunch of radars, including the recent Simrad 3G broadband radar.

http://www.pronav.no/gendocs/Practic...2011_Radar.pdf

Their conclusion was that the Simrad broadband is the dog's b****cks. It has a practical range of 12 miles, they say. The power has been doubled since the BR24 and the range is now not as dramatically less than pulse radar of the size we usually use on yachts. And the resolution is dramatically better.

Simrad have just announced another version of this, which they call "4G" (really abusing the terminology here, I think), which has some improved signal processing and, they claim, even better performance.

Broadband radar does, however, suck in heavy rain, apparently.

[sneuman]

Originally Posted by zeehag

until i sailed south this past spring, i never used any radar or other such device. on this trip i used radar 3 times-- just to see if something was moving and turned it off again. bash and barny are smart-- save for later. decide whether you reallly NEEED it or just WANT it.

The problem is that Colregs Sec.1-5 states that you use "all available means" to keep a lookout. In other words, if you have a radar, you MUST use it.

So, committing to a radar means committing to having it on whenever you're underway.

[David M]

I have what is called "broadband" radar, (which is a misleading term). If one manually adjusts the rain clutter setting it works fine.

[Dockhead]

Originally Posted by David M

I have what is called "broadband" radar, (which is a misleading term). If one manually adjusts the rain clutter setting it works fine.

Is it a BR24? What kind of realistic effective range do you get with it for, say, detecting ships?

[psneeld]

Originally Posted by David M

I have what is called "broadband" radar, (which is a misleading term). If one manually adjusts the rain clutter setting it works fine.

Even 2-4kw old style radar sucks in "heavy rain"...moderrate showers though with good rain clutter attenuation is impressive once you learn how to use it.

[David M]

Agreed, the rain clutter adjustment does not make things perfect again, just better than if there was no adjustment.

[Bash]

Amazing how often the radar and chartplotter disagree, where the radar is saying a breakwater, for example, is 1.5 clicks away while the chartplotter thinks it's still 2 clicks away.

Guess which one is right.

[psneeld]

Originally Posted by Bash

Amazing how often the radar and chartplotter disagree, where the radar is saying a breakwater, for example, is 1.5 clicks away while the chartplotter thinks it's still 2 clicks away.

Guess which one is right.

Depends on how well you can read a radar..I've had plenty of commercial fishermen fined even though they fished with Noah in the old days because they didn't understand some of the basics of radar...

Properly sorting the two sets of data or using a good system overlay eliminates that issue.

[Bash]

Originally Posted by psneeld

Properly sorting the two sets of data or using a good system overlay eliminates that issue.

That's entirely wrong.

I use an overlay system most of the time inshore. The problem lies with fundamental chart inaccuracy. The radar measures what's actually there.

[David M]

Radars generally don't lie. If it is saying something is there, then it is probably there, especially with really solid contacts like a breakwater or a channel marker.

There is occasional ghosting caused by multipath propagation but ghosting is usually pretty obvious. It has a certain pattern. With a radar overlay, if there is some ambiguity I almost always choose the radar over the chart.

This is what makes navigation an art, deciding through experience what is more likely to be true and what is probably BS.

File:Multipath propagation diagram en.svg - Wikimedia Commons

[conachair]

Originally Posted by Dockhead

Simrad have just announced another version of this, which they call "4G" (really abusing the terminology here, I think), which has some improved signal processing and, they claim, even better performance.

Broadband radar does, however, suck in heavy rain, apparently.

Simrads does look pretty cool though.

http://www.simrad-yachting.com/Produ...band-4G-Radar/

http://www.panbo.com/archives/2011/1...demo.html#more

2 scales on the same screen - nice

[Bash]

Originally Posted by David M

Radars generally don't lie.

The only time I've been lied to by a radar was coming out of Marina Del Rey in heavy fog. The radar kept showing boats traveling around 200 knots overtaking me from dead astern, spaced out at one-minute intervals. They kept coming and coming even though we never spotted one of them.

I finally realized I was on the takeoff flight path directly west of LAX.

[David M]

Hah..me too. I enjoy watching flights taking off and arriving at SFO and OAK when I am in the area. I tag them using ARPA. It's sort of a geek thing to do when I am not busy with other things.

[SailFastTri]

Originally Posted by Tortuga's Lie

SailFastTri,
Thanks for the comparison, that's the help I was looking for. As I said, I was leaning towards the broadband and since we're only traveling at 6 knots +/- storms don't approach that fast, at least not as fast as if we were on a power boat traveling at 25 knots....
Anyone else have first hand experience cmparing both types of radar?

One thing to add, is that with the BR24 broadband radar I can enter a harbor using 1/4 or 1/2 mile range and clearly see every channel marker and boat on a mooring, as separate marks. That's really useful at night or in pea-soup fog, especially considering many charted markers are moved due to storms, and many places have uncharted private markers. I could never get that level of close range detail out of the huge blobs on-screen with the 4kw radar it replaced.

If I need to choose between close detail of hard objects that present immediate danger, vs. longer range (beyond 8 miles) it's very easy to decide which information is of greater value for safety.

I almost never zoom out beyond 8 miles because I have AIS to "see" ships and am more concerned about losing close-in resolution to see smaller traffic. It appears from the PBO write-up Dockhead posted that the newer broadband radars give even better long range performance than my unit.

To me it seems like a no-brainer. If you already have a suitable multi-function chart-plotter then stay within your brand and use the best radar compatible with it. If buying a new MFD/C-P then I would choose (again) to go with one of the Navico brands that support the broadband radar technology.

If you care about integrating wind and engine and speed instruments with the MFD/CP (can't see why that would be important) then NMEA should let you mix vendors and have all the bells and whistles on one display.