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Full Version: [LW11] connecting an A70D chartplotter to a NASA GPS repeater
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I have NASA GPS repeater connected to my chart plotter - A70D. The repeater gives "no GPS signal". It is only when I put a course into the plotter that the repeater then comes up with a fix and works as expected, giving SOG etc.

This is a pain as every time I start up the instruments when racing I have to go down below to set a course on the plotter. The plotter is also connected to the same port to the VHF/DSC and gives a fix on startup there no problem.

I have rewired the NMEA junction box but still the same. I am using port 2 NMEA 4800 out of the plotter and have connected as per the NASA instructions with red to power, blue to NMEA +out and screen to NMEA -ve out.

I have been told this may be because NASA uses the old single wire and ground whereas raymarine use the newer NMEA +ve and -ve ? And it has been suggested I use a NMEA protocol bridge like this -


Will this work????? (and if so how to wire it ie NASA blue to yellow RX?). If not is there another solution Thanks
Dear adamcovell,

You are connecting the NASA GPS to the wrong connections, as you are sending a signal out of the GPS on NMEA you will will to go in on the A70D.

As follows

NMEA OUT GPS + > NMEA IN + (white) A70D
NMEA OUT GPS - > NMEA IN - (green) A70D

or you can use the other NMEA IN port on the A70D
Orange/ White is +
Orange and green is -

Many Thanks
Hi louise,

Thanks for coming back.

The NASA device is not a GPS receiver it is a GPS repeater. I have a Raystar 125 Plus GPS receiver that goes into the chart plotter.

I then want take the data out of the chart plotter to the NSA GPS repeater which is located in the cockpit. I only get data appearing there when I put a course into the chart plotter

I have attached a diagram of my whole set up that I used to re-wire things recently. You can see the Nasa GPS repeater in the middle.


Dear adamcovell,

Thank you for the response.

The RS125 when connected via NMEA0183 the shield/ negative needs to be connected to the NMEA0183 IN negative on the plotter. Looking at your diagram this would be the orange/ green coloured cable on the plotter.

Does this resolve the issue?

Many Thanks
I shall give that a go on the weekend .. thank you
I would add that you can see from the diagram I have 2 GPS receivers, 1 is plugged into the AIS (AIT1000) box and then connected into the port 1 of the chart plotter (A70d) . The second is the RS125 (into NMEA port 2).

When I reconnected these items i did the AIS first and powered up. This gave a fix straight away. I then wired in the RS 125 and it seemed to also work. This is how the boat was when i got it.

Is it a bad idea to have 2 GPS receivers connected like this? Could this be causing problems with the repeater?
Dear adamcovell,

Thank you for your post.

A AIS transceiver typically has its own dedicated GPS source and cannot use the GPS source that is for the network.

You can use the GPS source for the AIS to supply the network with GPS data when sending out on NMEA0183 on a low baud rate.

I would expect to see 2 GPS antennas in this case and looking at your diagram the AIS unit is connected only on 38400 baud rate keeping the GPS solely for the AIS.

Many Thanks
Thank you very much for your comments- all makes sense!
You are welcome.
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