Radar v Chartplotter interference

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david_steward

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I have a new Navman 5600 colour chartplotter. It works very well, except for when my 8 year old Raytheon R20X radar is transmitting.

After a variable amount of time, sometimes a few minutes, other times half an hour, the chartplotter crashes. The screen freezes and the unit has to be turned off at it's circuit breaker. More recently, the unit has crashed then performed a factory reset. There are no problems when the radar is in standby mode.

I have tried a multitude of possible fixes.

I have re-routed the gps antenna and the plotter power leads. I have connected the power leads to a different circuit breaker to the radar. There is no nmea connection between the radar and the plotter. I moved the gps antenna. I temporarily moved the chartplotter away from the radar display. No luck

After all this, I discovered that the plotter still crashes when it is not even connected to it's gps antenna.

The plotter is wired correctly, with the screen wire earthed to ground.

The two displays are about 12" apart. There is no scope for seperating them further. I have another gps, a Garmin 128 which is unaffected by the radar.

Is the interference likely to be in the DC power supply system?

Or direct RF interference from the radar scanner to the plotter display? They are at least 12 feet apart and not in line horizontally.

This is driving me nuts, coz as you would expect, both manufacturers feel the other's kit is the problem!

Any ideas?





<hr width=100% size=1>We don't want a sports cruiser, totally impractical. Err ok then.

Dave S
 
Reading all the things you have tried, it appears that the radar transmitting affects the digital electronics in the plotter. A few suggestions spring to mind, apologies if you've already tried them:
If moving the radar display has no effect, what about the radar antenna?
If it doesn't have a metal casing you could also try making a Faraday cage for the plotter display by wrapping it in baking foil (or something thicker if possible), which is connected to earth.
Make sure antenna screens (esp. the Radar) are earthed at a single point (not both ends) to avoid earth loops.
If the noise is getting in on the power supply you could try and fit a common-mode choke to each, even some ferrite beads on the power lines might help.

Good luck

<hr width=100% size=1>
 
Reading all the things you have tried, it appears that the radar transmitting affects the digital electronics in the plotter. A few suggestions spring to mind, apologies if you've already tried them:
If moving the radar display has no effect, what about the radar antenna? (easier said than done I know!)
If it doesn't have a metal casing you could also try making a Faraday cage for the plotter display by wrapping it in baking foil (or something thicker if possible), which is connected to earth.
Make sure antenna screens (esp. the Radar) are earthed at a single point (not both ends) to avoid earth loops.
If the noise is getting in on the power supply you could try and fit a common-mode choke to each, even some ferrite beads on the power lines might help.

Good luck

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Thanks for your reply, I will try the foil approach.

Sorry for my ignorance, but please can you explain exactly what a common mode choke is, where I would get one, and how to fit.

Many Thanks

<hr width=100% size=1>We don't want a sports cruiser, totally impractical. Err ok then.

Dave S
 
If you go to www.farnellonline.co.uk and look at component No. 870-742 you will see an example. It is a pair of chokes (inductors) on the same ferrite and will remove high frequency signals that appear on both lines, which is what you will have if the power line is picking up the radar transmission. They are usually between the power supply and whatever on-board regulation there is. The one I pointed you at is a bit more than that, is called simply an in-line filter, having a couple of capacitors to improve its efficiency as well. Costs about a tenner, depending on current rating, places like Maplins and Tandy ought to do them as well.

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Whilst agreeing with the previous replies, they are a probable culprits. It may be that the interference is from the Radar antenna and is being picked up by the GPS antenna. If non of the previous suggestions have any effect you may have to move the GPS antenna around to different locations and see if that works.

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Thanks for your reply, but as I mentioned, the plotter crashes even when it's gps antenna is disconnected.

This has lead me to discount the gps antenna as the source of the problem.






<hr width=100% size=1>We don't want a sports cruiser, totally impractical. Err ok then.

Dave S
 
I don't have a solution but I can offer these points. I have Garmin plotter and Raymarine radar display mounted within a few inches of each other on the chart table. Both are connected to a supplementary fuse/switch box beneath the table, cable length about 18 inches. I have tried to keep the antenna cable well separated from the radar scanner cable, although I understand that this has no bearing on your situation. I have not experienced an plotter crash problems.

I would infer from this that you are maybe experiencing RF interference. Is the scanner mounted in a position that the plotter could be receiving direct transmission? Check the vertical angle that the scanner transmits, adding 50% for exaggeration. Only other thing I could suggest is that you rig a temporary power supply for the plotter and check it where there is no possibility of interference.

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I had another two thoughts about your problem. If you disconnect the GPS antenna but leave it open circuit it may be picking up the radar signal nearly as well as with it connected. If it is a passive antenna you should be able to put a short circuit between the antenna core and screen. If the plotter still crashes then the pickup is in the circuit board or power line as you already suspect. If not, it could be through the antenna. It is a good point from the other two about the radar antenna as well, although it is unlikely on a small boat you will be able to move it very far anyway. Vertical seperation is more important than horizontal, obviously. It would be interesting to try another (identical) plotter to see if it is a fault or a design feature, but again that may be easier said than done.

The other thought was why the plotter might be crashing at all. Check the power connections for the radar and especially the plotter for corrosion or dodgy joints, all the way back to the battery and including any fuses. If the plotter is having to draw its current through an effective resistance, and the radar is dipping the battery volts a little when it pulses, the plotter electronics may be suffering voltage dips rather than direct RF interference. It's a long shot, but connection problems account for 90% of all electronic faults.
Good luck.

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