New radar

[MarkJohnson]

Having just fitted and commisioned a Furono 1722C radar, I used it in earnest on a night sail over the w/e, on my Sadler 32 (Mast Mounted)

Very pleased with it, but was surprised that the radar image seemed to be about 10 to 20 degrees out of true. The unit is connected to GPS for the plotter operation (also impressive) but not to an electronic compass.

As a result, I can only use the head up mode. I have read the manual fairly carefully, but cannot find a method of calibrating the heading and thus skewing the display to show the bearings better.

I have looked at the mast head unit, and it seems to be aligned pretty well.

Am I expecting too much? In thick fog in a shipping lane, I would be hoping that the bearing to targets would be reasonable, if I am to avoid collision. That was the main point of buying the unit.

regards

Mark Johnson



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[StephenW]

Mark - the JRC 1500 has a software means of re-aligning the display so I'm sure yours must have this facility too. Have you tried the Furono website (assume they have one)?

Agree radar gives a lot more info about whats nearby

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[Talbot]

The radar only gives more information if you know how to interpret it and how to set the controls to provide the best picture - otherwise it can give you a totally false confidence.

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[MainlySteam]

Am not familiar with the 1722 (which I think is a radar/plotter), however, in case no one comes back with the definitive answer the following may help. I believe, from memory, that on the Furuno dedicated radars (certainly the higher level models) that if one hits the Menu key one can then select an "Others" or similar option. When selected that then gives you another selection of options one of which is "Installation Setup" or such like. I believe that you will find the alignment you need under that, should your unit follow a similar menu pattern.

John

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[jonjo]

Re: Yawn

The guy has an installation problem, he is not looking for a generic lecture.

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[Jools_of_Top_Cat]

I have just commissioned my radar after an agonising wait due to a cable fault with the unit. I tested mine in earnest during daylight and at one point had a buoy and a yacht ahead and a yacht following us up the channel to Porthmadog.

So there I was looking at screen while motoring in, popping my head up through hatch to see what the radar was seeing and back to screen, well practice init!

Anyhow I had decided that I had a somewhere near 7° error to stbd when in head up. On the Raymarine sets I think it is called 'bearing alignment' and looks a little like the fine tuning bar that appears on some televisions, where you see the pointer scroll on the bar as you adjust.

So I adjust it out to where the screen looks about right, but after a few sweeps it is obvious I have gone too far, so I start bringing it back little by little, using autopilot now instead of SWMBO pilot. Little bit here, little bit there, right, perfect, I got a position I was very happy with.

I read off the screen, back to 0° alignment! I put it down to tiny movements of the boat pushing out the error on the screen, I am actively looking for a good fluxgate now to run in stabilised (course / north up). I am not suggesting this is your error, but just noting something I found with multiple small targets in daylight.

Probably best setting it up from a harbour wall or fore and aft mooring on a dead calm day, I would say pontoon but there are so many masts and boats all around you may have a problem distinguishing a good target.

Hope this helps.


<hr width=100% size=1>Julian

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[MarkJohnson]

Thanks to all. I will look at the installation set up again.

The 1722c is a chart plotter as well, which I bought at the boat show. I think that a compass added to the system will enable me to overlay the chart onto the radar screen (vice versa!) which will give spectacular results in shallow water areas.

Regards

Mark J



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[Talbot]

Re: Yawn

That is why my comment was in response to the statement <<Agree radar gives a lot more info about whats nearby >> and not to the original poster. It is also aimed at all those people who buy the radar (and GPS) and believe that they are getting the whole picture without understanding the factors that effect it.

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[Oldhand]

Re: Yawn

Calibrating the radar heading marker should be a standard installation task as it will only be correct by fluke on a new installation. It is a very important thing to get right and I can't beleive this particular Furuno doesn't have a mode for setting it up. The calibration should be done by using a small target, i.e. a buoy, with the minimum gain to obtain an echo and comparing the bearing of the centre of the echo with a bearing accurately obtained by other means. A useful way of confirming that the echo being used is the target you are intending to use is to make the target a waypoint and if the echo and waypoint marker are coincident, then it is very likely to be correct.

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[bedouin]

This may seem obvious - but if you don't have an electronic compass how can you expect the radar to give a north up display?

I suppose it could make an approximation using CoG but that is likely to be inaccurate to the point of being dangerous in some situations

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[Wiggo]

That's exactly the issue, AFAIK. It can only infer CoG from successive GPS fixes, so at slow speed on a yacht, it will be hopeless at guessing where north is. You can correct the alignment for head up display in the setup, but to get North up requires a fluxgate compass. That will let you have North up, but for chart overlay, AFAIK you need a high speed fluxgate, poss with a rate gyro. Either way, you need 10 fixes/sec for overlay. Bank on around £500+VAT for the kit, or thereabouts.

<hr width=100% size=1><A target="_blank" HREF=http://homepage.ntlworld.com/graham.wignall/boats/eulimene600x800.jpg>The old and the new</A>