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Old 12-02-2021, 18:52   #16
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Re: Raymarine Seatalkng/N2k Losing GPS/AIS signal

So I completely removed the old GPS device and it happened again today.

The new GPS is at the masthead and is away from EM interference outside of the VHF (besides this was happening before we had it).

My only conclusion is that the chartplotter is malfunctioning somehow since it now appears that this only happens when the chartplotter is on (I left the instruments running all last night and it did not happen). So I am going to disconnect the chartplotter from NMEA 2K and see what happens.
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Old 12-02-2021, 20:22   #17
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Re: Raymarine Seatalkng/N2k Losing GPS/AIS signal

If the new gps is at the masthead and is n2k, then the run up to it has to be the backbone. That means it must be terminated at the masthead.
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Old 13-02-2021, 10:59   #18
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Re: Raymarine Seatalkng/N2k Losing GPS/AIS signal

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Originally Posted by zboss View Post
So I completely removed the old GPS device and it happened again today.

The new GPS is at the masthead and is away from EM interference outside of the VHF (besides this was happening before we had it).

My only conclusion is that the chartplotter is malfunctioning somehow since it now appears that this only happens when the chartplotter is on (I left the instruments running all last night and it did not happen). So I am going to disconnect the chartplotter from NMEA 2K and see what happens.

Let's see if I understand your configuration and issue.


  • You have an E125 with an internal GPS.

  • You have a Raystar 125 GPS that was connected via NMEA 183, but is now disconnected.

  • You have an N2K based GPS at the top of the mast. Brand not specified. This is attached to the backbone via a short spur cable at the top of the mast and that the NMEA/Seatalk backbone is properly terminated at the top of the mast.

  • You have an AIS transciever with its own GPS connected to the N2K/Seatalkng backbone. Brand not specified

  • You have some data display of some sort, I70 or Autopilot control that you can see the GPS position data with the E125 turned off.

  • You have gone to the data sources menu on the chart plotter, set the data source to manual and selected the N2K as the default data for GPS?



When you have the chart plotter connected to the backbone the system looses GPS position at random times. With the Chart plotter off the GPS position displayed on the other instrument is stable. When the chart plotter is on and the Seatalkng/N2K spur cable is disconnected from the backbone the GPS on the other instrument is stable.
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Old 14-02-2021, 14:42   #19
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Re: Raymarine Seatalkng/N2k Losing GPS/AIS signal

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If the new gps is at the masthead and is n2k, then the run up to it has to be the backbone. That means it must be terminated at the masthead.
Its not the new GPS. The OLD GPS had the exact same problem. The new GPS has a brand new cable and is self terminated.

It appears that the OLD GPS isn't the problem either.
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Old 14-02-2021, 15:19   #20
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Re: Raymarine Seatalkng/N2k Losing GPS/AIS signal

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Let's see if I understand your configuration and issue.


  • You have an E125 with an internal GPS.

  • You have a Raystar 125 GPS that was connected via NMEA 183, but is now disconnected.

  • You have an N2K based GPS at the top of the mast. Brand not specified. This is attached to the backbone via a short spur cable at the top of the mast and that the NMEA/Seatalk backbone is properly terminated at the top of the mast.

  • You have an AIS transciever with its own GPS connected to the N2K/Seatalkng backbone. Brand not specified

  • You have some data display of some sort, I70 or Autopilot control that you can see the GPS position data with the E125 turned off.

  • You have gone to the data sources menu on the chart plotter, set the data source to manual and selected the N2K as the default data for GPS?



When you have the chart plotter connected to the backbone the system looses GPS position at random times. With the Chart plotter off the GPS position displayed on the other instrument is stable. When the chart plotter is on and the Seatalkng/N2K spur cable is disconnected from the backbone the GPS on the other instrument is stable.
Almost right. All the equipment, including the instruments, lose GPS signal using either antenna - but not my phone.

The VHF is also not the cause. Lost GPS last night with no one around and the VHF off.

The equipment never loses wind speed, wind direction, or anything else on that mast head. We never lose depth, speed (well occasionally but that is expected of the UDST800 under certain circumstances), or temp from the sounder unit.

I haven't completely dismissed the idea that something outside of the nav system on our boat is causing GPS interference but multiple phones and ipads never lose a signal.
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Old 14-02-2021, 16:49   #21
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Re: Raymarine Seatalkng/N2k Losing GPS/AIS signal

Is gps stable when you aren't using the atopilot?
Is by any chance your autopilot a raymarine s1/2/3 and somebody hooked up the red seatalk connection the NMEA2000 network?
I have seen some strange malfunctions with this scenario.


Otherwise, I would look at gps priority problems on the network.


Edit: I see that you have isolated the problem to the plotter.


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Old 14-02-2021, 18:13   #22
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Re: Raymarine Seatalkng/N2k Losing GPS/AIS signal

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Originally Posted by zboss View Post
Almost right. All the equipment, including the instruments, lose GPS signal using either antenna - but not my phone.

The VHF is also not the cause. Lost GPS last night with no one around and the VHF off.

The equipment never loses wind speed, wind direction, or anything else on that mast head. We never lose depth, speed (well occasionally but that is expected of the UDST800 under certain circumstances), or temp from the sounder unit.

I haven't completely dismissed the idea that something outside of the nav system on our boat is causing GPS interference but multiple phones and ipads never lose a signal.

The wind speed and direction, assuming they are Raymarine are not coming from the mast head directly. They are analog signals that go to an ITC-5 which translates them into NMEA 2000 if you have an I70 or read them directly if you have the older I50 or I60 series. If you have the older ones they would not be affected by a problem on the N2K bus.



You state that the N2K GPS is self terminating. How is it plugged into your Seatalkng bus? If it is plugged into a spur connector and has a terminator on it that could cause all kinds of problems on a Seatalk Network. It would have to be plugged into the backbone and while Seatalk NG supports N2K spur connections it is not clear to me that they support NMEA 2000 extensions to the backbone.



OK I just looked it up and they do support this configuration, but they caution that it must be connected through an adapter cable to the backbone connection and that there be only two terminators on the entire system, one on the Seatalk bus and one on the N2K bus. Results are unpredictable if there are more than 2. As you say the N2K GPS is self terminating then it must be plugged into the Seatalk backbone, not a spur access point and one terminator on the Seatalkng bus must be removed.



It is not beyond the realm of possibility that you have some sort of interference with GPS signals in your area, but the fact that phones seem to work and the E125 is both GPS and Glonass which operates on different frequencies this is unlikely. I take it that the problem existed before you added the N2K gps and that is why you added the N2K GPS, is that correct?
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Old 15-02-2021, 06:22   #23
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Re: Raymarine Seatalkng/N2k Losing GPS/AIS signal

Interesting... I have an Axiom12Pro and Axiom9 which do something similar - an error pops up “AIS connection lost”, and any current destination waypoint or route is cancelled.

When the “connection” is restored, the target list populates instantly (I.e. they were in the unit somewhere, they all appear too quickly to be newly received over the air). I infer that the “connection” is an internal software one, not a physical plug or wire.

At one time I had both serial NMEA0183 and N2K feeds for AIS. it seems a bit better with later firmware and the serial input disconnected. Sent many logs to Raymarine, which I was told were “like gold” but no feedback as yet.

In short, it could be software.
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Old 18-02-2021, 08:12   #24
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Re: Raymarine Seatalkng/N2k Losing GPS/AIS signal

I replaced the battery in my Raystar 125 yesterday and it's working fine again. The battery is a CR2032 and was a simple matter as the holder is exposed as soon as you take the back off of the unit.
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Old 22-02-2021, 06:48   #25
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Re: Raymarine Seatalkng/N2k Losing GPS/AIS signal

I finally tracked it down to a bad VHF cable with shielding exposed and apparently grounding incorrectly. I replaced the ends and all is good.

I did not know that RF interference on GPS could happen from a VHF even when receiving a signal that is practically non-existent. I fixed the cable and we seem to be back in business.
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Old 22-02-2021, 08:14   #26
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Re: Raymarine Seatalkng/N2k Losing GPS/AIS signal

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Originally Posted by zboss View Post
I finally tracked it down to a bad VHF cable with shielding exposed and apparently grounding incorrectly. I replaced the ends and all is good.

I did not know that RF interference on GPS could happen from a VHF even when receiving a signal that is practically non-existent. I fixed the cable and we seem to be back in business.
Are you saying a non-transmitting VHF cable was interfering with your GPS reception? That doesn't seem plausible. Was the cable also being used for AIS transmission?
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Old 22-02-2021, 08:28   #27
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Re: Raymarine Seatalkng/N2k Losing GPS/AIS signal

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Are you saying a non-transmitting VHF cable was interfering with your GPS reception? That doesn't seem plausible. Was the cable also being used for AIS transmission?
It may not be plausible but it happened! and no... we have a different antenna for ais.
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Old 22-02-2021, 08:53   #28
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Re: Raymarine Seatalkng/N2k Losing GPS/AIS signal

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It may not be plausible but it happened! and no... we have a different antenna for ais.
Well then, I'll be interested in the physics when someone smarter than me explains it on CF
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