LCD Radars

[longjohnsilver]

My current CRT radar has stopped working and I am looking to replace it but want a clear display. I am told that the latest LCD radars give good definition but read that CRT is still best. If you have experience of LCD radars I would be interested to read your comments.
Thanks.

 

[Guest]

I have an LCD radar Autohelm LCD vintage 1996, fairly cheapy job, not v expensive, and everyone moaned ooh that's no good. But it seems fine, and I need it about twice a year, recently for long trip in France.

It's on a non-flybridge fairline targa, and when in use I trim the bow down to ensure full forward looking picture. In the med, sometimes sunny in parts, very foggy in other places, I can confidently plane well offshore so long as I have crash-stop visibilty for floating objects, and as long as if see summink you turn hard 45 degrees or more to port if anything on bow 3 miles away(so obv not these speeds unless 5+ miles off shore)

Incidentally I wd say that the most important thing abt radar is to use it quite a lot in complete daylight. Then you know absolutely what a sailboat, a small fishing boat, a ship all look like on the screen, and you know that you have all the adjustments just right. Good game too- I can fairly relaibly tell wife where the seagulls are around the boat by radar. I've not used CRT but I wdn't need anything better.

 

[Guest]

Re: oh and waterproofiness

the ahelm has had a very good spalshing (massive waves all over dash) and although other stuff hs packed in, this hasn't. Obv not an issue if you are inside.

 

[longjohnsilver]

Re: oh and waterproofiness

Thanks Matt. I along with most other people would only have to use radar in anger a few times a year so it is interesting to hear your views. If my set were to get wet it would either mean the windscreen had shattered or the boat was sinking - in which case I wouldn't really care about hitting anything else!!!
John

 

[ArthurWood]

LongJohn, The only problem I have found with LCD in hot sun, eg Florida, Bahamas, is that the screen goes black and requires a shade to prevent this. That introduces a problem if, like I do, spend a lot of time standing at the helm. The shade obscures the screen if it is mounted in the dash.

 

[Guest]

I've seem both and my own is CRT. The LCD units seemed a bit harder to read in strong light but were basically OK. Also the backlighting for night use was pretty uneven on the set I saw and definitely inferior to a CRT set.

Re usage, I agree with Matts that it is important to use radar in the daylight so that you understand what a various targets look like. My boat is in the water the year round so that I am often returning to the marina in the dark when its use is essential. Even in daylight I find that the radar will often "see" things before I do (probably down to my ageing eyesight) and from that perspective its a good all round safety feature.

Finally, I have a flybridge boat and, unlike many, the radome is mounted a good height above the helmsman's head when seated. It is not when you stand and for that reason I would not use the radar when conning the boat from the flying bridge (although perhaps micro waving my brains would help nowadays). I have seen many modern boats where the radome is simply not mounted high enough for safety, especially on flybridge boats. No doubt someone will tell there is no health hazard from all these powerful microwaves but I prefer not to test the theory.

Nick

 

[Bergman]

Nick

This is something I have wondered about myself. I see quite a few flying bridge boats with the radar only a small distance above head height, When one considers the vertical beamwidth there must be some irradiation of people on the flybridge.

I watched 4 RN inshore patrol boats the other week coming into the marina, all with a big radar scanner on an arch only inches above head height. Three out of 4 had the radar going even in the marina.

Is there an health hazard?

Compared with a mobile phone there must be a much greater foeld from a working radar.

I remember once talking to a chap who had been sparks on a cableship. He reckoned that it was "normal" practice to stand infront of the scanner for a few minutes before going ashore to prevent leaving any "reminders" with the local population.

Many a true word spoken in jest

 

[Guest]

Many years ago I worked for a defence contractor where we had a radar that could knock down birds - they would hit the ground ready cooked!

BUT what's important is the energy involved. Power output (measured in kW) is energy output per second i.e. kJoules/second. If you look at the spec of a radar set, a 2kW set might have a power consumption of 45W. This means that while it puts out 2kW of radar energy, it does it as a series of very short pulses, which average less than 45W.

So a mobile phone might bang out 0.5W right next to your ear, but it's an inverse square law - double the distance, and the power goes down by a factor of four. So to get about a mobile phone's worth of radiation out of your 2kW radar set, you would have to run round 24 times a minute in front of the radome, with your ear 4 inches from the scanner. Given the size of a 2kW radome, you'd need to have your head 5" inside the dome to get the 4" from the array.

There are clearly a number of technical problems associated with irradiating yourself this way, so I'm inclined to believe the manufacturers on this one when thay say the damn things are safe.

BTW, if anyone can work out a way of running around a radome 24 times a minute without tripping over things, please let me know

 

[Guest]

any idea why the Navy lot leavem on whilst at anchor? Is rules that they do this, for keeping watch?

Also anyone any idea if the twirly Furuno radar detectors are better than the domes? Or the same. Spose at least you you can see if its knackered. Any other differences?

 

[jfm]

Re: Do they fry your brains?

Matts the twirly has 2deg beam width while the radome has 4deg. So twirly better picture definition

Graham, I agree all you say. I posted on this subject a long time ago and then looked into it further. As you say the output is in pulses becuase the input is much less. Our radar is 4kw output but less than 100w average input. Also the beamwidth is 2deg so sitting on the flybridge you only get 2/360 of the 100w potentially frying your brain, and that is further reduced by the inverse square law as you say. Hence I don't worry anymore, and I figure they're no worse than a mobile phone or a dodgy microwave oven, or probly this PC I'm whacking right now (64" plasma of course). Now, where did you get that pic?

JFM

 

[Guest]

Re: Do they fry your brains?

what pic?

 

[Guest]

For reasons of reliability, rather than using an electric motor, the Navy uses hand turned radars. These are operated by the lookout by means of pedals. The Captain can therefore tell at a glance if the lookout is awake, from just about anywhere in port.

 

[Bergman]

Thanks for that

I am somewhat reassured about the unfryed brains of our gallant sailors.

I do remember however the TV pictures from the Falklands. The picture broke up completely each time the radar scanner went round. Perhaps these machines had rather more than 2kW.

I also remember siting in the car out side RAF Linton on Ouse some years ago. About a mile from their radar scanner. The car radio went off at each sweep of the scanner.

I don't worry personally, having once subsisted for 4 days on McDonalds "food" I guess my brain is too spongy to be affected

 

[Guest]

Yesssss, well that's military stuff for you. I seem to remember the bird cooker pumped out several megawatts...