Would a radar detector work? - Page 2 - SailNet Community
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post #11 of 17 Old 01-13-2011
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Originally Posted by chrisncate View Post
Don't radar detectors work line of sight though?
Yes I'm sure they do - sorry don't know what else to do with the question.

Perhaps you mean "It doesn't tell you where the radar signal is coming from". Well, it doesn't matter where it is coming from, the purpose of a detector isn't to locate the radar source, just to warn you that there is one. Locating the source is down to your eyesight or your own radar.

I apologise if I've missed the point.

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post #12 of 17 Old 01-13-2011
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Actually the CARD does tell you the approximate direction the signal is coming from ( N,S,E or West) and has a signal strength bar.
From their website -"If the C.A.R.D. antenna is mounted on your stern rail and has an unobstructed view, you should receive an indication if there are any radar emitting ships. The overall range is 5 - 8 NM for most merchant traffic."
Used it for one atlantic crossing , but as I previously said it won't work with your own radar system on, and I also found that either NOT all ships have their radars on or the CARD missed some.
Next trip I purchased a Furuno radar, previously had another small radar, and used the watchman mode extensively- worked much better for me especially since I was singlehanding.
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post #13 of 17 Old 01-13-2011
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It would depend on the height of the radar emitter and the height the CARD unit is mounted at. The higher they are, the greater the range.

Originally Posted by chrisncate View Post
Lol, I am such a horrible communicator... sorry about that! It's even worse in real life. I am socially retarded basically.

I meant to question wether or not radar goes over the horizon, and if it does not, isn't the horizon closer than 24 miles? Would the radar detector go off if the source of the radar was over the horizon?


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post #14 of 17 Old 01-13-2011
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Formula (approx distance) d = 1.2246* SQRT(h); d in miles with h in feet.

Using this, you get 3.87 miles distant at a 10 foot height; 5.47 miles at 20 feet. 50 feet up gets you out to 8.659 miles. This is, ostensibly, distance to the horizon so taller objects 'over' the horizon could still be visible. Light refraction also affects the truly visible range... might not affect radar.

This method does not account for the curvature of the earth. Consider how "far" you could(n't) see sitting in a life raft.....


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post #15 of 17 Old 01-13-2011
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For the mathematical challenged there is a nomogram for estimating distance on page xii.


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post #16 of 17 Old 01-14-2011
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Well you just got all the good links Jackdale.

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Re: Would a radar detector work?

AIS detector is the gadget you are looking for, some newer vhf radios come with them already built into the radio transmitter.
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