Spurious ARPA Targets DRS25A-NXT

[Quitsa]

I have been bothered for some time by the excessive number of targets that are automatcally selected and tracked by my radar. The attached was taken with the gain and sea clutter set to "auto" with adaptive sea state. Almost none of the targets are boats or other objects that one might want tracked. I end up clearing all targets frequently to clean up the display. Usually the radar picks up the boats first and then starts getting all of these spurious targets.

Any ideas what causes this or how to mitigate it?

 

[FishTech]

The typical causes of that are the heading sensor not being properly calibrated and aligned, the radar "antenna heading align" not being accurate, or something installed on the vessel within the radar beam.
Do you have any installation photos?
Can you post a picture of the radar data in the sensor list? I've seen two cases of the 25ANXT having an FPGA software that does not match the app software.

 

[Quitsa]

The typical causes of that are the heading sensor not being properly calibrated and aligned, the radar "antenna heading align" not being accurate, or something installed on the vessel within the radar beam.
Do you have any installation photos?
Can you post a picture of the radar data in the sensor list? I've seen two cases of the 25ANXT having an FPGA software that does not match the app software.

The heading data is coming from an SCX-20. It appears to be perfectly aligned. For example, if I am going straight towards a nice clean fixed target such as the entrance buoy to my harbor, the target will show on screen exactly on the heading line. Also the chart overlay lines up perfectly.

There is nothing at all mounted in front or to the sides of the radar antenna array. The tower pipework, outrigger bases, and various items such as VHF antennas are mounted aft of the radar in a 120 degree or so sector. They don't seem to cause interference because I can see targets astern quite well and in any case, the spurious targets are generally forward in the sector with no obstructions.

I will check the software versions shown in the sensor data and post what I find. I recall installing the radar software update issued last year -- I wonder if that is the problem, though I think it was doing this before.

 

[Quitsa]

Here is the current installed software on the DRS25A-NXT:

 

[FishTech]

Your software is good. 01.11:01.05 is what we want to see on the open array NXT radars.
Do you recall resetting the ARPA settings after the update? That might clear it up.

 

[Quitsa]

That may well have been the problem. As it happens, yesterday I was updating the DFF-3D software from the sensor update package and decided to reinstall the radar software while I was at it although it already had the latest version. I came across that instruction on resetting to factory default and reset all the radar and ARPA settings to factory default. It seems to have fixed or at least greatly mitigated the issue. I saw only a couple of spurious targets getting tracked, which possibly may have been birds out of visual range. It was quite calm so the next test will be what it does when there are returns from waves.

Thanks.