Broadband/Digital radar for yachts

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BlueSkyNick

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I have a 1996 Autohelm simple radar with 2kW scanner, but it still works fine. When I upgrade, I will go straight to digital, but want it to be developed, fully supported, and sensibly priced before I do.

Chatting recently to an electronics engineer trained by Raymarine in this stuff was interesting. Apparently, Simrad and Garmin have an offering which takes the analogue signal from current scanners, via a convertor into a digital display unit. Raymarine have a HD product, which includes a new scanner so the whole system is digital end to end. Pricing will be competitive, because Raymarine need the market penetration and sales volume. Downside is that only a 4kW scanner will be available, no 2kW, and the digital system consumes more power.

Allegedly, take one look at the system, and you stop worrying about the power consumption !!

Anybody had any real life experience yet?
 
I've not seen anything of these new systems, but I'm inclined to take the various claims as containing a certain amount of marketing hype. AFAIK, the beam width, and hence the definition, of a radar pulse is dependant on the antenna size. That's the laws of physics in operation. I've not seen or read anything that suggests that the antenna of a "digital" set is basically different from existing designs, just that the return signal is processed somehow to provide a sharper image. This may be an improvement, but a silk purse cannot be made out of a sow's ear, and small boats will continue to be stuck with small antennas operating in the existing frequency band, or am I missing something?
Re "broadband" radar. There was a lot of publicity about a year ago, but it doesn't seem to have made much impact yet.
I think the terms "digital", "HD" and "broadband" have great hi-tech advertising appeal !
I too would be interested in any views.
 
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HD radar is supposed to work in a different manner to the traditional radar - it (iirc) sends out a continuous signal at changing frequencies - so as it is aware of what it sent out and when - when that frequency is returned it knows how far away it is and depending on if surrounding frequencies are returned as well - knows how big it is ... at least - that's how I read it - could be wrong!

As the technology has moved on so we can expect far better definition out of it - one downside may be that it takes more power - and I can't think how RM will take an 'analogue' scanner and make it as good as the digital version ... but I guess that remains to be seen.
 
[QUOTE HD radar is supposed to work in a different manner to the traditional radar - it (iirc) sends out a continuous signal at changing frequencies - so as it is aware of what it sent out and when - when that frequency is returned it knows how far away it is and depending on if surrounding frequencies are returned as well - knows how big it is ... at least - that's how I read it - could be wrong!

[/QUOTE
That description is broadband radar, which has been reviewed and seems to have good resolution but only over very short range. Press comments also suggest that it is very susceptible to interference and reflection.
The technology is not new and the small craft version was to be available early this year. I suspect that the problems aren't yet solved.
The link given above for the Raymarine HD spec. gives a beam-width of 3.9deg. for a 24 inch antenna. That's the same as for "normal" pulse radar. As a cynic, I remain to be convinced!
 
I'll have to wait till the current one goes TU ... it's raymarine stuff - so no telling how long it's got ... it'll probably wait until the prices go up then die ... that's usually the way. :(

Hmmm - seemed to have managed to reply before your post ... Does that mean Christmas comes early for me or late for you?

Dan - this is getting rediculous - please SACK the pillocks that manage your servers and get someone in there who can SYNCRONISE THE TIME ... it ain't that difficult ... I manage across 7 different locations ...
 
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earlybird said:
[QUOTE HD radar is supposed to work in a different manner to the traditional radar - it (iirc) sends out a continuous signal at changing frequencies - so as it is aware of what it sent out and when - when that frequency is returned it knows how far away it is and depending on if surrounding frequencies are returned as well - knows how big it is ... at least - that's how I read it - could be wrong!

[/QUOTE
That description is broadband radar, which has been reviewed and seems to have good resolution but only over very short range. Press comments also suggest that it is very susceptible to interference and reflection.
The technology is not new and the small craft version was to be available early this year. I suspect that the problems aren't yet solved.
The link given above for the Raymarine HD spec. gives a beam-width of 3.9deg. for a 24 inch antenna. That's the same as for "normal" pulse radar. As a cynic, I remain to be convinced!
Click to expand...

I guess they could use pulse-compression techniques to reduce the pulse length; that would improve the range resolution significantly, but would require a much higher bandwidth in the transmitted pulse, and also significant real-time processing capability - the "conventional" way of doing it using travelling wave tubes may not offer sufficient longevity for consumer goods.

As far as azimuthal resolution goes, you could improve things by using some form of deconvolution. However, for this to work you'd have to have a very high PRF, so that samples were spaced at small angles.

Realistically, neither will work with an existing antenna; you'd certainly have to have something optimized for a broader band-width and then you might as well use something capable of a narrower beam-width. Phased arrays, anyone? No moving parts!
 
Having talked with the Navico Product Expert (the Professor who is Officer in Charge of Broadband radar which sells through the Simrad, Lowrance and Northstar brands), I am convinced of the following,

1 Being a new technology, it will benefit from strong development

2 It currently suffers from interference from other radars, but work to reduce/elliminate this has progressed well since its first launch. What this means in practice (say thick fog when entering Portsmouth) I do not know.

3 Tests of using installing it underneath a conventional pulse radar for simultaneous use have not been carried out. Therefore, additional tests are being carried out given this scenario.

Would I buy one? Not until I know the interference issues have been nailed. I want to know that when I am close to another vessel, its radar is not going to cause havoc with mine.
 
Beam width and resolution aren't directly related. The wider the beam the less accurate the bearing usually (though that's not 100% true either) but it's never wise to rely on basic radar for an accurate bearing anyway.

Resolution is fairly vague term when used in radar by marketing men but it is often taken to mean the ability to pick out individual targets. FMCW (Navico's Broadband for example) excels at this, especially at close range where there's no massive pulse to overpower the receiver. It also effectively gives more information back to processor to interpret and produce the display.

Processing even a pulsed radar signal digitally can make a massive difference though - think of the advances these days in face recognition software, image enhancement, audio noise removal and so on. When even a pocket camera can recognise not just faces but whether or not they're smiling we shouldn't be surprised that a radar set can interpret a radar return and put an enhanced image on a screen. They all work the same way - they look for a recognised pattern in a huge amount of data (or they look for something that doesn't fit the pattern and remove it).

Technically it's wrong to claim that digital radar improves resolution as the as un-processed resolution is the same but the software "guesses" where the actual target is inside the return; in practice it gets it wrong so rarely it's not a problem.

I think Panbo did run a conventional radome and a Broadband radar on the same arch without problems but found there was some interference from other boats - one comment made was that they hadn't tested it in areas of heavy shipping so they hadn't had 10' arrays throwing mega-watts down it's throat. I'm sure the problem is easily fixable though as the military systems solved it many years ago with just some clever filtering.

Edit: this is the link to the Panbo tests http://www.panbo.com/archives/2009/08/18_radomes_3_weirdness_edition.html. Hardly a definitive test I agree...
 
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