[floatsome]

Here is a photo of my Northstar chartplotter's power/data cable. There are two black wires. I presume...

1. I can run the flat black wire that is bare inside the cable (and continuous with the shield) to DC negative.
2. I can run the shiny black wire that is probably also ground and presumably continuous with the flat black wire/shield to the Brown wire on the Uniden VHF (in their manual: "GPS ground") for NMEA. The NMEA output wire from the GPS is white and connects to the green"GPS data in" wire, it seems to me.

The manual for my model (550i) does not explain those two black wires, but the Navman manuals online look similar (Northstar was Navman), so presumably my interpretation is correct.

Have I got it right?

 

[eolon]

Hello:

The bare wire is the shield drain wire. It should only be terminated at one end. Which end is the trick. the convention is that the shield is connected at the source only. In the case of a depth transducer, for instance, the shield is terminated at the transducer, and not connected at the instrument end.

Connecting both ends creates a ground loop and makes the signal very noisy - the shield essentially acts like an antenna and picks up all the noise in the boat. I would be very suspect of connecting your shield wire to a ground of a VHF or anything else - this is a ground loop waiting to happen.

On some Navman / Northstar instruments (the depth 3100) there is no black wire, and they expect you to use the bare shield wire as the negative or ground. Not a good design.

I would try wiring everything but leave the bare wire unconnected first; if everything works, then leave it unconnected.

NavBus NMEA standard wiring is yellow and white wires, unless wiring to a Repeat 3100, which uses yellow, white, and green as NMEA.

This:http://www.navmanmarine.net/upload/Marine/Internet_Manuals/install/navbus_eng_web.pdf <http://www.navmanmarine.net/upload/Marine/Internet_Manuals/install/navbus_eng_web.pdf> has a schematic of the NavBus junction box, which details all the connections and wire colors that Northstar and Navman use.

Best Regards,


e

.::.

 

[scottyt]

it looks like the flat black wire is a shield braid, the foil gives it a better shield, but harder to connect. they probably just heat shrink it so it stays together and is easy to connect. i would say to connect it to as close to the battery as you can, to give it the best shielding ability.

i think the cable just has a foil and a braid shield, not a big deal, but a good design

 

[floatsome]

Thanks for the information, but I still am fuzzy on details about the various ground wires.

The Navman manual you pointed me to shows the same diagram in Navman manuals I found, clarifying that the shield is shrink-wrapped so that it can be connected to something, but they are not clear on what to do with it. One Navman manual I found says either black wire can be connected to ground (presumably boat's DC-negative), and that they are connected inside the cable. But I want to connect the NMEA GPS-to-VHF wires too. So, I have two problems: picking the right GPS wire to connect the GPS to DC-negative, and picking the right GPS wire to connect to the VHF's ACC cable Brown wire.

The Northstar manual does not specify whether the shiney black wire is "NMEA ground", or just a common ground. It does not mention that there are two black wires in the power-data cable.

The Uniden customer support knowledge base gives this:
"Here is the basic wiring method between the Solara DSC radio and a GPS: (+) Radio GPS data IN wire (GREEN) TO (+) GPS/NMEA data OUT wire; (-) Radio GPS ground wire (BROWN) TO (-) GPS ground wire". Is that any DC-negative ground wire, or a special NMEA ground wire?

The VHF's manual tells me to connect its Green to "GPS data in" (that would be Northstar's White NMEA out wire in the power/data cable), and its Brown wire to "GPS GND", but I can't figure out which GPS wire to use. Can I just run it to boat's DC negative ground, or is there something special about the NMEA module's ground wire signal?

To add to the confusion, the radio's ACC cable also has a thick Black wire labelled "DC GND", which obviously can connect to boat's DC-negative, but it is not clear whether it is necessary to hook that one up too. http://www.uniden.com/pdf/solara%20dsc-BKom.pdf

What if I connect this way?

1. The GPS shiny Black wire to boat's DC-negative.
2. The GPS White wire to VHF Green "GPS data in".
3. The VHF Brown "GPS GND" to boat's DC-negative (or does it have to be a ground from the NMEA module in the chartplotter??).
4. Leave the shield "wire" (flat black) unconnected?
5. Undecided about the black wire in the ACC cable of the VHF (the main red and black power cord wires are already connected and the radio works).
6. The VHF ACC cable thick black wire to boat's DC-negative.

 

[eolon]

Leave the shield drain wire unconnected. It is connected to the -DC internally and should not be connected, in order to act properly as a shield for RF noise.

The VHF "GPS GND" is the other wire of the NMEA signal - the white wire from the chartplotter.

The "GPS IN" wire from VHF (green) should go to the Navman Yellow wire.

THe VHF "ACC" thick black GND goes to a boat ground (-DC). Do not connect it to the NMEA gnd. If at all possible, connect this wire to the same ground point that the chartplotter is connected to. Connecting it to a different ground location on the boat may let the radio "float" at a slightly elevated voltage above ground and misbehave.

So:

1. The GPS shiny black to boat ground
2. GPS white to VHF brown
3. GPS yellow to VHF green
4 No connection: shield wire
5. VHF black ACC wire is a external speaker gnd and is not connected unless you have an external speaker.
6. THe VHF ACC thick black to boat gnd (not NMEA gnd)

That should work...

If it doesn't work =) try swapping the GPS NMEA wires, yellow and white (I wish companies wouldn't use "IN" as a designation - "+" makes it easier to connect stuff.)



Best Regards,


e

.::.

 

[floatsome]

So:
1. The GPS shiny black to boat ground
2. GPS white to VHF brown
3. GPS yellow to VHF green
4 No connection: shield wire
5. VHF black ACC wire is a external speaker gnd and is not connected unless you have an external speaker.
6. THe VHF ACC thick black to boat gnd (not NMEA gnd)

The Northstar GPS manual says to combine the yellow and black wires (doesn't say which black wires) and connect them to DC-negative when connecting the unit to power, and says GPS white is NMEA out to a device like the VHF. The GPS yellow wire is connected separately after the ignition switch for a switching situation that allows for auto power off, so in this case it is not NMEA out from the GPS. The colour codes must somehow be different. I'm going to have to try to get through to Northstar, I guess. Thanks for helping.

 

[eolon]

The Northstar GPS manual says to combine the yellow and black wires (doesn't say which black wires) and connect them to DC-negative when connecting the unit to power, and says GPS white is NMEA out to a device like the VHF. The GPS yellow wire is connected separately after the ignition switch for a switching situation that allows for auto power off, so in this case it is not NMEA out from the GPS. The colour codes must somehow be different. I'm going to have to try to get through to Northstar, I guess. Thanks for helping.

Hmm... I have a NavMan 550i Chartplotter and it doesn't say what yours is saying at all. Weird.

Best Regards,


e

.::.

 

[floatsome]

Hmm... I have a NavMan 550i Chartplotter and it doesn't say what yours is saying at all. Weird.

This is indeed wierd. Here is the Navman Tracker 5500i manual: http://www.navmanmarine.net/upload/Marine/Internet_Manuals/5500_5100/5500_5100_eng_web.pdf. See page 35, which shows the same colour codes as the Northstar 550i, but provides a bit more information than my Northstar manual. That page says this about the black shiney wire: "Pin 1 Black Ground (power negative, NMEA)", which suggests to me that it can be wired to both DC-negative for chartplotter power and NMEA ground on the VHF. It says this about the flat black wire: "Note: Shield is connected to pin 1, black wire", which as you suggest could be left unconnected, for the reasons you provide. About the yellow wire: "Auto power in (connect to positive power in to enable auto power)".

 

[floatsome]

No wonder I'm having trouble getting this sorted out. From
http://www.bmea.org/wp-content/uploads/2007/08/nmea-guide.pdf

"There are only two wires involved - how difficult can it be? Well, although you can’t do any damage if you get the wires the wrong way round, the major problem with NMEA interconnection is that there is no set reference standard with regarding to NMEA connections - the two wires can be any colour and the terminals can be called anything - NMEA Data and Common, NMEA + and -, NMEA A and B and so on. Some manufacturers don’t have a dedicated Common terminal, in which case you have to connect the common wire from the other unit to the battery negative of the equipment you’re interfacing with."

and

"Reading the various user manuals you will then find that there is little consistency when it comes to references for the NMEA connections - some talk about NMEA Data and Common, others NMEA + and - or even NMEA A and B. Whatever they call them you basically have a wire that supplies data, plus a return wire. Don’t be distracted by the wire colours of any cable that might come with the
unit - there is no colour standard for NMEA cables and it will vary depending on the manufacturer and which cable they are using.".

I have emailed Northstar tech support.

 

[floatsome]

Apparently this will work:
1. Boat's DC negative to shiney black wire.
2. VHF's NMEA- to boat's DC negative.
3. Leave shield wire unconnected.
4. GPS white wire to VHF NMEA+.

I've got power to the chartplotter now, but can't test the GPS to VHF NMEA link until after the boat is outside and the chartplotter can see the sky.