Connecting a gps receiver to a Nasa Clipper GPS Repeater

[Thors]

Could anyone help me? I'm trying to connect a masthead gps receiver with 5 wires (shielded large black wire,red wire,green wire, yellow wire ,black wire) to a Nasa Clipper GPS Repeater (black,red and blue(data)wires). What should I connect to what?

 

[ithet]

Firstly, you need to tell us what GPS receiver you have.

Secondly, why is your GPS receiver mounted on the masthead? For accuracy they should be mounted as low as possible (not like a VHF antenna).

 

[Thors]

Thank you for replying. It's a Topgnss receiver.

 

[Thors]

The five wires are labelled as follows,but there is no other information:
Green-RS232tx
Red-12v
Yellow-RS232rx
Both black wires-gnd

 

[prv]

GPS green to NASA blue. One of the black wires (the signal ground) should be connected to the NASA black, but it’s not clear which one. In practice, connecting both to the power supply negative will probably work.

Agree that the GPS receiver shouldn’t be at the masthead - moving it forty feet closer to the satellites won’t make any difference, but moving it around rapidly as the boat pitches and rolls will make it harder for it to figure out where it is.

Pete

 

[GHA]

Do you know what baud rate the gps receiver is set transmit at? The Nasa receives at 4800bps,

 

[MikeCC]

I don't think you're going to get much out of the NASA Repeater with that setup. It's main benefit is using it with waypoints from a GPS plotter so you can easily see course and bearing to waypoint, XTE plus a 'rolling road' display. I'm not sure it will even give you SOG without a waypoint. You'll be able to see your position though, and feed it to VHF as well if needed.

I'd echo comments about receiver location. Place it low down to minimise relative movement.

Agree with prv on connections. Could be that one black is nominally power ground and the other is signal ground for convenience.
If it's outputting NMEA, default baud rate should be 4800.

 

[[3889]]

A while since I had a NASA GPS repeater ( a great bit of kit IMO) but I think it can only display NMEA from a master GPS, not process a signal from an antenna. Not certain on this so stand to be corrected

 

[prv]

I think it can only display NMEA from a master GPS, not process a signal from an antenna.

This is true, but the unit the OP is connecting it to is a GPS, not an antenna.

Pete

 

[MikeCC]

A while since I had a NASA GPS repeater ( a great bit of kit IMO) but I think it can only display NMEA from a master GPS, not process a signal from an antenna. Not certain on this so stand to be corrected

Difference between GPS receiver, which OP has, and GPS antenna. Former processes signal and provides data, latter only a signal, like a TV aerial. A GPS antenna usually has coaxial cable and BNC or TNC connector.

 

[prv]

If it's outputting NMEA, default baud rate should be 4800.

That is the default for true NMEA0183, but a lot of things nowadays use NMEA sentences at faster baud rates. Receivers with a 5v power input often default to a 38,400bps data rate, for example. This one accepts 12v so the chances it’s been configured for 4800 are a little higher, but it’s not impossible that it could need to be changed. Should be possible using a PC and serial port, and either a terminal program or possibly the manufacturer‘s proprietary software.

Pete

 

[[3889]]

Difference between GPS receiver, which OP has, and GPS antenna. Former processes signal and provides data, latter only a signal, like a TV aerial. A GPS antenna usually has coaxial cable and BNC or TNC connector.

OK, something new to me. What is the advantage of having an external receiver (presumably with no display?) rather than an antenna, whether it be mounted at deck level or masthead?

 

[prv]

What is the advantage of having an external receiver (presumably with no display?) rather than an antenna, whether it be mounted at deck level or masthead?

That you can connect it straight to whatever needs to know position (a VHF, an AIS receiver, a plotter without an integrated GPS of its own...) without needing any intermediate box in between. Incidentally, the reception is likely to be improved by eliminating any long runs of co-ax; the receiver is millimetres from the antenna, inside the same housing.

Pete

 

[Thors]

Do you know what baud rate the gps receiver is set transmit at? The Nasa receives at 4800bps,

The GPS receiver is set to 9600bps as default, so I will have to reset it to the 4800 rate which the repeater accepts. What method would you recommend I use to do this?

 

[Thors]

GPS green to NASA blue. One of the black wires (the signal ground) should be connected to the NASA black, but it’s not clear which one. In practice, connecting both to the power supply negative will probably work.

Agree that the GPS receiver shouldn’t be at the masthead - moving it forty feet closer to the satellites won’t make any difference, but moving it around rapidly as the boat pitches and rolls will make it harder for it to figure out where it is.

Pete

Many thanks for your replies - very useful

 

[prv]

What method would you recommend I use to do this?

Whatever method its manual specifies.

Pete

 

[GHA]

The GPS receiver is set to 9600bps as default, so I will have to reset it to the 4800 rate which the repeater accepts. What method would you recommend I use to do this?

Only what Google says, some windows software did seem to be around, likely you'll need a serial /USB adaptor to get a Windows machine to talk to the GPS.

 

[MikeCC]

The GPS receiver is set to 9600bps as default, so I will have to reset it to the 4800 rate which the repeater accepts. What method would you recommend I use to do this?

Usually using some sort of terminal software and sending a command.

Did you see my post about using the NASA Repeater in the way you plan?

 

[[163233]]

I'm not sure it will even give you SOG without a waypoint.

It just repeats what it gets over nmea, so if the nmea input is providing SOG and COG it'll display it.

 

[GHA]

It just repeats what it gets over nmea, so if the nmea input is providing SOG and COG it'll display it.

Which nmea sentences?

I couldn't get mine to display anything sending RMC position unless a route was active in opencpn sending some sort of route nmea, can't remember which sentence.

From the manual>
USING THE REPEATERPress POSN. at any time, and the repeater will display the current position (Lat and Long) after a brief pause while it collects the fresh NMEA data from the receiver. Unless a waypoint is selected on the receiver, this is usually all the data available to the repeater.