False target

[northcaptain]

I have a false target/echo appearing on my DRS4D (Navnet3) at approximately 2 miles at bearing 300 degree. The radar is mounted aft starboard (transom) and there is the mast of the boat in front. But the main bang have been adjusted. Is there a way to diagnose and troubleshoot that false target in order to get rid of them ?

If there is no guard zone it is only an annoyance but if i define a guard zone which include that false target, it creates many Arpa proxies over time.

Thanks

 

[Johnny Electron]

It sounds like a ghost image caused by a radar reflection or water. If you get water inside a radar dome or array it will cause ghost images/reflections. You might open your dome and inspect it for water. If everything is good, then it is most likely a radar reflection from something on your boat. You can get a good idea of what it is, by using your TX SECTOR BLANKING feature of the NN3D. (MENU – SYSTEM – RADAR tab) You can blank (not transmit) your radar in each sector and reduce the degrees until you narrow down what the radar is bouncing off of. Then you would need to remove the item causing the reflection, or relocate your radar scanner to avoid it. In some cases, if the item is behind you; the TX SECTOR BLANKING can be used to prevent the reflection and leave the scanner in place. I would not advise making a “Blind spot” to the front of the boat by using this feature.

 

[northcaptain]

Hi Johnny

Thanks for the help in diagnosis this issue. There is no water inside the cover, by chance. I have not tried the sector blanking yet. I will for sure. What i can say though is that there is really nothing in the apperture of the radar except the mast (it is a sailboat and the mast is about 10 inches large). The radar is mounted aft on a dedicated pole and the mast is about 15 feet in front of it. But the ghost image is shown 2 miles away. I thought the "main bang" and radar optimization could reduce the interference caused by close local objects - do you think it can be the mast that is producing that kind of ghost image ?

Andre

 

[Johnny Electron]

Can you please post some photos of the installation and the radar image? Please also include a photo of the radar with the sea clutter at zero. What is your mast made of? Since your radar is aft starboard and the image is 300 degrees, it makes since that it could be your mast causing you reflection issues, especially if it metal of any sort.

 

[northcaptain]

I will go out on water tomorrow and will take pictures of the radar screen with sea clutter at zero. In the meanwhile here are pictures of the installation. It is true that both the mast (aluminum) and the sail furler (aluminum extrusion of about 1 inc diameter) are in front of the radar and at an angle to port of the radar. But they are so close that i thought the radar optimization and main bang adjustement would remove them from the radar map.

Is my understanding correct ? I admit knowing nothing to the way a radar works internally...altought i can use one.

Regards

Andre

 

[Johnny Electron]

Main Bang suppression is only going to blank the display of the "Main Bang" ball of video you normally get in the middle of the screen. It will not keep your magnetron from firing signal or going out and striking objects. When you have an object close to your scanner, especially metal, it will cause the RF energy to reflect/bounce. The only way to change that is to move the radar, move the object causing the reflections, or use sector blanking and stop transmitting into the object. Just like your eyes, the radar is not going to see through the metal. Worse, it will reflect and cause you to see spots. What many sailboats do is mast mounting the antenna and set sector blanking to prevent the transmission into the mast. You might have luck by relocating the antenna, but your problem is no doubt all the metal you have in front of you.