How to tell when someones radar is left on?

[a64pilot]

Guy’s yes, the Radar detection feature is neat, but that’s not what makes it such a good piece of kit.
It’s a transponder, meaning instead of a tiny weak little return signal off of your little fiberglass boat that the ship may very well never see, it sends an active return signal making you very, very visible. I’d say like a supertanker but I don’t know that.
As I said the normal return signal from a Radar pulse is extremely low power, so even a tiny weak transmitter puts out much, much more power than the normal return.

1980’s I built a police Radar Jammer off of readily available plans, it’s output power was tiny, maybe 1/10 of a watt but probably less, making it safe to use. Anyway what made this one nest was it was frequency adjustable, so you could send out the frequency that would correspond with 100 mph or so and the Cop would have no idea what was going on, cause it was plain no one was going 100 mph in that school zone, or set it low to send a 20 mph return for the freeway etc.
Unfortunately you have no way of knowing other than low or high speed what was being sent, it wasn’t that sophisticated and it was only X Band I believe.

[a64pilot]

Plus a Radar receiver has an enormous advantage over a Radar transmitter, the receiver will work for a very much longer range as it receives the full output power, while the Radar itself only sees the very much weaker return.

[Viking Sailor]

Sorry a64pilot but the Echomax Active must first detect/receive the radar signal before it sends an echo. Thus, if it can only detect the radar's signal if it is within 400 feet the echo received by the radar will appear to be 400 feet or less away.

[thomm225]

Originally Posted by Viking Sailor

I looked at getting one until I read on their site that the detection range for the new low power radars is measured in feet. These were designed for detecting the high power pulsed radars.



I do have a C.A.R.D. radar detector that due to its low power consumption turning it on when my radar is off. I don't expect that it is any better at detecting the low power radars then an Echomax Active.

Thanks for that info.

Still feet are still better than nothing.

I would never be able to sleep very well anyway if I were single handing at night and still sailing so I would be totally alert to anything different especially an audible alarm.

Scroll down in the link below for response distances on various radars

https://www.echomax.co.uk/faq.html

[a64pilot]

Originally Posted by Viking Sailor

Sorry a64pilot but the Echomax Active must first detect/receive the radar signal before it sends an echo. Thus, if it can only detect the radar's signal if it is within 400 feet the echo received by the radar will appear to be 400 feet or less away.

Yes, any transponder only replies to a received signal, first used to my knowledge in WWII for aircraft, and has been the basis for air traffic control for a very long time.
Without a transponder first it’s often unlikely that Air traffic control will even get a “skin paint” and if they do all they know is something is at X location, with a transponder they know who and know their altitude too, now with ADSB they know airspeed also as well as rail number direction of travel etc.
Read the second paragraph under Rationale to understand why it’s almost certain the the Echomax will always receive that signal, and it’s going to reply I’m sure almost instantaneously.
https://en.m.wikipedia.org/wiki/Low-...ntercept_radar

Your going to know your being painted long before the other Radar knows your there.

Now what I flew had the AN/APR-48 RFI or Radar Frequency Interferometer, which is a very sophisticated radar detector,
https://www.lockheedmartin.com/conte...B-brochure.pdf
what it could do among other things is give an exceptionally accurate angle of arrival for threat Radars, so you can’t determine range to the Radar on one hit, but you can know extremely accurately exactly the direction on which it lies, get a couple of more hits and the computer can triangulate it and tell you precisely where it is.
Also if there are other aircraft and they are networked together then the slight difference in the angle of arrival can determine exactly where that Radar is.

All that is to try to show that a radar receiver has a huge advantage over the Radar, think of a man walking around in a dark field at night with a flashlight, he can only see what the beam illuminates of course, if your on the edge of the field then of course you have him in sight the whole time.
You are the receiver, you’ll detect him a long ways before he detects you.

But your not trying to hide from him, in fact you want him to see you, so your receiver triggers your own lantern, lighting up 360 degrees, he’s going to see you then, that lantern is your transponder transmitting.

Now I have no experience with the Ecomax myself, it could be junk for all I know, but the theory is sound and is what 70 yrs old or so?

[NorthernMac]

I’ve seen aircraft and airport radars cause RF interference.
Had a guy try to do a photo shoot for a aircraft even, had one of those remote wireless flashes, he couldn’t understand why it was going off on it owns, pointed at the radar, every time it would sweep past off the flash would go.

Also always good to be thoughtful of your bright lights, radar, wake, etc around others.

My money would be it messed with his TV or Bluetooth speakers or something.

Originally Posted by a64pilot

Yes, any transponder only replies to a received signal, first used to my knowledge in WWII for aircraft, and has been the basis for air traffic control for a very long time.
Without a transponder first it’s often unlikely that Air traffic control will even get a “skin paint” and if they do all they know is something is at X location, with a transponder they know who and know their altitude too, now with ADSB they know airspeed also as well as rail number direction of travel etc.
Read the second paragraph under Rationale to understand why it’s almost certain the the Echomax will always receive that signal, and it’s going to reply I’m sure almost instantaneously.
https://en.m.wikipedia.org/wiki/Low-...ntercept_radar

Not sure about that, I’ve had ATC call primary targets for me quite a few times “primary target only, altitude and type unknown”, even had them call possible bird activity. Lots of the airport radars can even show cars on the roads by the airport.

[a64pilot]

Originally Posted by NorthernMac

I’ve seen aircraft and airport radars cause RF interference.
Had a guy try to do a photo shoot for a aircraft even, had one of those remote wireless flashes, he couldn’t understand why it was going off on it owns, pointed at the radar, every time it would sweep past off the flash would go.

Also always good to be thoughtful of your bright lights, radar, wake, etc around others.

My money would be it messed with his TV or Bluetooth speakers or something.





Not sure about that, I’ve had ATC call primary targets for me quite a few times “primary target only, altitude and type unknown”, even had them call possible bird activity. Lots of the airport radars can even show cars on the roads by the airport.

They can if they are close to the traffic, but with a transponder it increases their range greatly.
Which is exactly what we want on our boats right, not only to be seen, but to be a large bright target when far away.

They can see cars depending on how they have their Doppler notch adjusted, a Doppler notch is of course based on Doppler shift and is a way to filter out all stationary targets, or targets below a set speed to eliminate ground clutter.
You can use the Doppler notch to defeat threat Radar by making sure your closing speed is lower than its Doppler notch, a fixed wing can do that by flying a circular route spiraling in towards the Radar.

Of course a standard pulsed Radar can tell the speed of an object by knowing precisely the frequency transmitted, then the difference in frequency of the return signal will equate to a speed, due to Doppler shift.
The Longbow Radar on the Apache would often display highway traffic as aircraft due to their speed, no ground vehicle on the battlefield cruises at 80 MPH.

What I have yet to figure out is how a FMCW Radar which sweeps frequency up and down handles Doppler shift. You see it knows range by knowing the exact time the frequency that is received was transmitted, since the speed of light is a constant it can compute distance.
But a moving target will change return frequency and would therefore interfere with range estimation.
I assume it just ignores Doppler shift assuming nothing is going very fast on the water?

I’ve called B&G tech support and I don’t think they know, or at least the guy I talked to didn’t.

[Viking Sailor]

From the Echomax FAQ:


Active X RTE response to FMWC - Broadband radar.

Solid state- FMWC - broadband radar use a low transmit power which has steadily increased since their introduction 10 or more years ago. In the early days the Simrad 4G used 0.165 watts transmit power which was not enough to be picked up by the Active X - XS in normal sleep mode outside a range of 200-300m. Fortunately the power increases are now sufficient to activate the Echomax Active RTE and respond as shown below for the various listed makes.



These ranges are in comparison to 100% trigger at ~7nm for X and S band high power ship's radars.

[requiem]

Regarding hard-to-detect radars, I'd assume one way to start is by ensuring your signal is below the noise floor, but still have equipment sufficiently sensitive to detect the echo. How to extract the echo would be similar to processing GPS signals, which IIRC are also below the noise floor.

As to the FMCW Radar, I'm not a radar person and only know the basics, but I think this might help a bit:
https://www.radartutorial.eu/02.basi...0Radar.en.html

[Cherod]

Originally Posted by Terry Moffatt

I came into a anchorage the other night and forgot to turn my radar off right away. About a half hour later someone yelled over that my radar was not turned off. I appreciated that and quickly turned it off, but wondered … how did he know it was still transmitting?

you could just have asked him,, and then apologised .

[a64pilot]

Originally Posted by Viking Sailor

From the Echomax FAQ:


Active X RTE response to FMWC - Broadband radar.

Solid state- FMWC - broadband radar use a low transmit power which has steadily increased since their introduction 10 or more years ago. In the early days the Simrad 4G used 0.165 watts transmit power which was not enough to be picked up by the Active X - XS in normal sleep mode outside a range of 200-300m. Fortunately the power increases are now sufficient to activate the Echomax Active RTE and respond as shown below for the various listed makes.



These ranges are in comparison to 100% trigger at ~7nm for X and S band high power ship's radars.

But that is “trigger” range and not detection range correct?
One would assume that you wouldn’t want to trigger a transmission for every detected signal or you would be transmitting towards Radars that had no chance on picking you up, one would assume that to trigger a transmission that received power would have to meet min power.

I wonder if they publish a detection range, or is the alarm and trigger points the same to make is simple and prevent false alarms?

The Radars in the chart. Some are ships Radar’s aren’t they? 3 GHz is S band and us little guys don’t have S band do we?

[EmeraldCoastSailor]

Can my radar interfere with someone's else radar? I have never seen other's radar interfere with mine; well at least I never detected any interference. For years I have always assumed the radar reflector tube that I hang below my spreaders on a pennant halyard was "good enough". Never thought about an active radar reflector before this post.

[Viking Sailor]

Originally Posted by a64pilot

But that is “trigger” range and not detection range correct?
One would assume that you wouldn’t want to trigger a transmission for every detected signal or you would be transmitting towards Radars that had no chance on picking you up, one would assume that to trigger a transmission that received power would have to meet min power.

I wonder if they publish a detection range, or is the alarm and trigger points the same to make is simple and prevent false alarms?

The Radars in the chart. Some are ships Radar’s aren’t they? 3 GHz is S band and us little guys don’t have S band do we?

Trigger range is when the big ship can begin tracking the little stand-on sailboat. And yes, the JRC S-Band radar has an 8 foot antenna with a 96 nm range. So, if a big guy doing 16 kts start tracking the little guy at 4 nm that gives the big guy 15 minutes to track the little guy and figure out how to get out of his way. Or not!!!

[a64pilot]

Trigger range has to surely be when the transmitter is triggered.
If it were detection range, then that shouldn’t vary by much.

Assumption is that trigger range would be a function of the transmitter power of the received Radar, and that chart seems to bear that out.

[a64pilot]

Originally Posted by EmeraldCoastSailor

Can my radar interfere with someone's else radar? I have never seen other's radar interfere with mine; well at least I never detected any interference. For years I have always assumed the radar reflector tube that I hang below my spreaders on a pennant halyard was "good enough". Never thought about an active radar reflector before this post.

I believe but do not know that they are so sensitive to frequency that one will ignore the other due to slight variations in frequency, but I’d bet get them close enough and they would interfere.
I think it’s partially similar to why one cell phone doesn’t interfere with the others. Maybe a bad example.

I get people upset telling them this, but that little tube doesn’t do much.