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Old 03-08-2017, 11:25   #1
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Does having my radar transmitting make me more visible to others with radar?

I use radar almost all the time because I feel it increases my situational awareness in the crowded waters I sail in. Had a thought about it today though: If my radar transmitter is pulsing out radio waves, doesn't that signal get picked up by other vessel's radars and thus make me a more visible target?
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Old 03-08-2017, 11:39   #2
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Re: Does having my radar transmitting make me more visible to others with radar?

Having your Radar on does nothing to help increase your "radar signature" as seen by other vessels. Radar works by bouncing the signal "microwave" off an object then measuring the time for it to return, as well as calculating the direction from which the bounced signal returned. To increase your "radar signature" use a radar reflector on your mast that will "reflect" inbound radar signals from other vessels. AIS on the other hand allows other vessels to know here you are, the speed you are making, etc. So having both is a great idea! I hope that helps!
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Old 03-08-2017, 12:24   #3
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Re: Does having my radar transmitting make me more visible to others with radar?

Hey Captain Mark,

Thanks. Makes sense. I understand the basics of how radar and AIS work and I've always got my reflector up there.

If it does nothing to increase my own signature, then I guess my question is more technical - what makes the waves sent out by my radar different from the waves sent out by other radars - and how do the units differentiate between their own signal bouncing back and a signal that's coming from another unit.
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Old 03-08-2017, 12:34   #4
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Re: Does having my radar transmitting make me more visible to others with radar?

Not too technical, but put simply, it's all about the pulses of energy. And the timing of those pulses.

Yours does not exactly match the echo that the other radar is expecting on return.


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Old 03-08-2017, 12:46   #5
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pirate Re: Does having my radar transmitting make me more visible to others with radar?

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Not too technical, but put simply, it's all about the pulses of energy. And the timing of those pulses.

Yours does not exactly match the echo that the other radar is expecting on return.


If you want the longer version: As the emitter/detector array is highly directional it would have to be pointing precisely at you at the moment your radar fired off a pulse in that precise direction. The beam spread is about 2 degrees so that there is about a 1 in 180 chance of that happening if the other radar was not rotating and just facing you. Since both radars are rotating the probability multiplies and there is a 0.000028% chance of the synchronous situation being reached. Gotta love the smart people that figured that one out for us
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Old 03-08-2017, 12:47   #6
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Re: Does having my radar transmitting make me more visible to others with radar?

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Hey Captain Mark,

Thanks. Makes sense. I understand the basics of how radar and AIS work and I've always got my reflector up there.

If it does nothing to increase my own signature, then I guess my question is more technical - what makes the waves sent out by my radar different from the waves sent out by other radars - and how do the units differentiate between their own signal bouncing back and a signal that's coming from another unit.
I'm thinking your radar "waves" are not different from others but sent out at a different times.

Your radar is probably a pulse radar. So it has a pulse width.

I worked on an old air traffic control radar (still used on Navy Amphibs) that had a Pulse Width (PW) of 833 microseconds (or 833 millionth's of a second)
with a 40 mile range

A radar nautical mile is 12.36 microseconds. It would take 123.60 microseconds for the echo to travel back from 10 miles out.

The receiver will only be able to "look" for these echos during the PW time part of which is dead time when the transmitter was on and the receiver off so as not to harm it.

It would be quite hard for another radar to sync up with yours and cause interference I'm thinking

And then there's the rotation
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Old 03-08-2017, 13:24   #7
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Re: Does having my radar transmitting make me more visible to others with radar?

I see someone has had a go at answering that question. its a bit more complicated than that though. During the Falklands war, Argentinian pilots flew with there radar switched off, (when on final approach to targets) but they had radar detection, When the red light went on in the cockpit, they dropped lower, until it went off, eventually they were at sea level, then they released there exocet, the british ships couldn't see them, because they detected the radar transmission from the ship, then avoided it, and the british ships couldn't see there radar because it was switched off.
I don't know the full ins and outs. but if you decide to go in stealth mode, switch off your radar, it can get picked up, thats how they bombed the Iraq radar stations, bombs that home in on the radar transmission.
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Old 03-08-2017, 13:33   #8
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Re: Does having my radar transmitting make me more visible to others with radar?

Very interesting. Thanks guys. Makes sense... I guess I was looking for "the longer version".

To atlantical's point - Totally. I could have sworn I got the idea of having your own radar being a giveaway to enemies from reading about combat aircraft trying to stay stealth.
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Old 03-08-2017, 13:34   #9
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Re: Does having my radar transmitting make me more visible to others with radar?

A bit on how your radar may 'see' transmissions from other radars here.. https://books.google.com.au/books?id...spiral&f=false

And how to fix it here .. http://furuno.custhelp.com/app/answe...n-radar-screen

Those spiral lines used to be quite common years ago in busy waters... but I hadn't seen it for a long time before I retired ... I assume a certain level of IR is built in these days .
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Old 03-08-2017, 15:12   #10
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Re: Does having my radar transmitting make me more visible to others with radar?

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Originally Posted by Peregrine1983 View Post
I use radar almost all the time because I feel it increases my situational awareness in the crowded waters I sail in. Had a thought about it today though: If my radar transmitter is pulsing out radio waves, doesn't that signal get picked up by other vessel's radars and thus make me a more visible target?
No, RADAR is all about range finding, hence the name. A pulse from your RADAR will be discarded from any other radar receivers.
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Old 03-08-2017, 15:35   #11
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Re: Does having my radar transmitting make me more visible to others with radar?

While commercial radar will not detect other radar transmissions, the radar antenna is a pretty good reflector by itself. Whether rotating or stationary it increases your radar signature significantly.

If you want to detect other ship transmissions then you need to have a radar detector, similar to what you have in the auto world but check the frequencies and transmission pattern of your potential target.
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Old 03-08-2017, 18:31   #12
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Re: Does having my radar transmitting make me more visible to others with radar?

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While commercial radar will not detect other radar transmissions, the radar antenna is a pretty good reflector by itself. Whether rotating or stationary it increases your radar signature significantly.

.....
Only partly true; it only increases your radar signature in the direction it is pointing (stationary or not). So to be seen by the distant radar, both antennas have to be pointing at each other (within a few degrees); as this isn't likely most of the time, it doesn't increase your signature most of the time.
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Old 03-08-2017, 19:41   #13
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Does having my radar transmitting make me more visible to others with radar?

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Originally Posted by atlantical View Post
I don't know the full ins and outs. but if you decide to go in stealth mode, switch off your radar, it can get picked up, thats how they bombed the Iraq radar stations, bombs that home in on the radar transmission.

No, the Iraqi radar installations were taken out by Apache helicopters led by MH-53 helicopters because back then the Apaches did not have GPS
http://foxtrotalpha.jalopnik.com/des...lic-1753466057

However as the Air Force is the agency in charge of releasing all aerial combat footage and the Army downplays the air assets it has, very little usually gets out.
Being very familiar with what the Apaches video looks like, I can tell you a surprising amount of footage attributed to the Air Force on the news is actually AH-64 footage.
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Old 03-08-2017, 19:45   #14
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Does having my radar transmitting make me more visible to others with radar?

For many years there have been Wild Weasels that carry HARM missiles, or high speed anti radiation missiles, or missiles that seek and destroy Radar transmitters.
It is a very complex and dangerous mission, and there are all kinds of special assets to deal with radar, many, many assets that spoof it, cause it to display false targets, jam it, destroy it and lord knows what else.
https://en.m.wikipedia.org/wiki/Wild_Weasel
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Old 03-08-2017, 20:00   #15
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Does having my radar transmitting make me more visible to others with radar?

Your transmitting radar has no effect on a ships receiving radar.
However I believe that radar transponders exist for boats, that would give you a very large radar signal.
In WWII transponders were developed for military aircraft so that friendly radar installations could see them a long ways off and positively identify them as friendly, a transponder of course is a transmitter that transmits a signal that the other radar will see so to speak.


Just me but I don't think any of the radar reflectors we use on our little boats is as effective as we would hope. But they are better than nothing
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