RADAR DETECTION

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3reefs

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Keen to avoid being run down, but less keen to invest in a radar and worry about it running down the batteries.

I used to have something called a Lokata Watchman which was some help. It squeaked if we were being "painted" by another vessel's radar, and it gave an indication of the bearing.

Does anyone know what has become of Lokata, the Watchman, or even this whole technology and approach to collision avoidance?

Some months ago I saw a post about "CARD" (I think), but cannot now find it. Can anyone help, please?

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CARD - does it stand for collision avoidance radar detection?

It has four detectors , one per quadrant, so it gives you some indication of the direction. I was interested in one, but decided to go for a radar. Also the price for what amounts to just four simple amplifiers and an alarm circuit was unjustified.

I always wondred, if a simple microphone circuit and some op-amps, attached to and listening through the fibre glass hull to detect the prop-wash of a larger boat might not be usefull as a warning that another vessel is in your vicinity. That is I assume you have a sailining boat.

I cannot try this, I have a steel hull with internal isolation.

regards ongolo

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Tried the C.A.R.D. expensive unit for what its supposed to do my unit failed shortly after departing on an Atlantic crossing. suspect this was due to a nearby lightning strike, though nothing else on the boat was damaged. The failure was,nt total in fact it continued to detect nearby lightning strikes until I finally pitched it. Have recently installed a device called SEAME this is a radar inhancer, that is to say it apparently amplifies the echo return from your boat the manufacturer claims a x7 improvment in radar visibilty....it also indicates that you have been seen by another vessels radar but not nessesarily by the radar operator...

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A Hydrophone such as you describe will give a very false sense of security. You are likely to hear the propellor beat of ships on the beam, and those that have passed you. What you will not hear (and even submarines have some difficulty with, is the large bulbous bowed tanker coming straight for you, as his bulk hides the propellor from the detector.

Thus this system does not work for the most dangerous problem, only for thiose that either are not a problem, or are no longer.

50% of fog (i.e. Radiation Fog) is such that you will be using your engine anyway, and the latest radars are fine at only 2 KW. Thus the best detectors are those you rely upon yourself.

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CARD - does it stand for collision avoidance radar detection?

It has four detectors , one per quadrant, so it gives you some indication of the direction. I was interested in one, but decided to go for a radar. Also the price for what amounts to just four simple amplifiers and an alarm circuit was unjustified.

Well Sort of…..

I work on the aircraft equivalent of this, on Tornado’s and Harriers. I am not suggesting to be an expert, just thought I would try to add some cost clarification to the system you call CARD.

To attempt some cost justification, The CARD system should be able to receive a wide band of frequency, possibly 3GHz (10cm) up to 9.5GHz (3cm). This is no mean feat. Remember a dedicated radar only has to rx the same frequency as it pumps out, so you can use shared tuning etc. This card would have to be scanning at fast rates across the band.

µwave (microwave) amplifiers are extremely expensive and for this CARD system to do what has been said, the receivers and amps must be as near to linear across the band if some kind of directional ability is to be attempted, it will work in the same way RDF (radio direction finding) does, if the power rx’d in one receiver is more than the other, the target will seem closer to the higher power rx. This will ruin any bearing.

This kind of linearity across 4 quadrants at these frequencies is actually quite incredible; I am amazed someone has actually marketed these to amateur ‘non millionaire’ yachtsmen, seriously!

For the cost of one installation of the units I work on, I could seriously change my lifestyle and some. Ok it does a bit more, it is no secret that is can tell the pilot what threat he is faced with, but the receiver part of the installation is not a million miles from what the CARD promises.

I mentioned µwave amps, lets just say the stuff normally used does not have components, at these frequencies it will look like a bare circuit board, where a line of copper / gold can be a diode or filter etc. This is not Maplins technology. The really, really tricky bit is making a receiver ampilfy a frequency band of 6 GHz to ouput to the brain of the CARD a level power. That is what makes it expensive. Your FM radio will have a bandwidth of say 20 MHz and that takes fine tuning to get the amplifier correct, this unit has 4 matched 6GHz receivers.

Sorry to jump in, I just thought you might have been interested as to the high price tag of this kit.


<hr width=100% size=1>Julian

<A target="_blank" HREF=http://www.topcatsail.co.uk>Top Cat Homepage</A>
 
according to this link, it does indeed operate at 3cm to 10cm
No price though

<A target="_blank" HREF=http://www.mcintyremarine.com.au/card1.html>http://www.mcintyremarine.com.au/card1.html</A>

<hr width=100% size=1>There is no such thing as "fun for the whole family."
 
Talbot,

I see your logics and cannot contest that you are absolutely right.

regards and thanks

ongolo


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Hi Julian,

You are also right, but it was not me who called it CARD, it was the manufacturer. I tried to remember what it stands for.

Radar is a of course a specialized field and I am not into that, but I think it is like this.

If you like to process a signal you need certainly expensive amplifiers, but just to detect or not detect a signal makes one big difference to a circuit.

Compare the FM stereo transmitter/receiver complexity from hte studio to your radio with a remote controlled garage door. Both contain a radio transmitter/receiver, but the level of complexity is apparent.

So the manufacturer of CARD simply has to detect a signal, not decode it or process it in any way, but simply use the smallest amount of change in a bias to say "I am here". Further than to apply my logics and some knowledge of electronics (mostly digital C-MOS) designing with analog interfaces and what comes, I dont know. Maybe I am going to experiment with it one day?

By the way, how much do these radar detectors for a car cost and how complex are these gadgets? Just for interest sake, I dont know I live in a desert.

regards ongolo

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I'm putting a SeeMe on the new boat - the concept of big solid echo is likely to get someones attention, it means that if they are using ARPA they stand a better chance of being accurate, AND it gives me a visual indication that we have benn 'pinged' by a radar.

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I agree with what you say about just detecting a blip and setting an alarm, after all this is what the radar detectors in cars do init!

I have never heard of CARD until this thread, I am responding to what has been said about direction finding. I believe you are going to need more than a blip in order to achieve this, otherwise it will be so crude as to be useless.

Think of a scenario, a ship is steaming towards your starboard beam, a quadrantial (is that a real word???) system is going to rx the ships signal on 3 aerials, so the system will return information that the ship might be fore, stbd or aft..... how will you react to that.

Unless the real requirement is just to notify the skipper that there is a ship within 30 miles of his vessel, if that is really the case, I will agree more with you about cost and technoligy. But still, to build a 6GHz rx is not going to be cheap.

<hr width=100% size=1>Julian

<A target="_blank" HREF=http://www.topcatsail.co.uk>Top Cat Homepage</A>
 
there's a short reference to passive radar equipment contained within one of the MCA's projects (no 4xx something about AIS algorithms - you can find it on the MCA site). The opinion of the authors was that such devices are only of use in the very best of conditions ....

buy a radar might be best option .... ?


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Sea-Me

I have heard 1st hand anecdotal evidence that these are very good, and I have one on my shopping list. One worry though is that they are so good at 'magnifying' your radar presence that the other vessel might well assume that you are large enough to carry radar and to therefore be seeing him, and that consequently you will do your bit to keep out of his way.

<hr width=100% size=1><A target="_blank" HREF=http://www.writeforweb.com/twister1>Let's Twist Again</A>
 
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