Topic: 998c si hd NMEA out to Cobra radio - which wires?

[jjmoney]

Hello everyone, it's great to find this forum. A lot of good stuff here! Just what I was looking for. Thanks to all of you for creating this knowledge base.

OK so I have a question. I bought a boat that has a Cobra MR F75 radio. It used to take a NMEA signal from a Northstar GPS. I still have the tip and ring plug and wire that plugged into the radio. It was connected to a Northstar cable and took NMEA signal from the Northstar. The red and black on the radio cable connected to the white and black on the Northstar cable, respectively.

I recently installed a 998c HD SI. It has a pigtail cable that connects the GPS antenna to the plotter. The ACCY COM cable on the pigtail has 4 active pins, the 4 closer to the indented portion of the plug. I also have another pigtail from an older HB plotter. I can plug the ACCY COM plug (all 6 pins) of the new pigtail into the COM plug of the spare pigtail, and then plug a bare wire plug into the NMEA COM plug (4 corner pins) on the spare pigtail, which leaves me with 4 live wires on the bare wire cable. Black, red, green, white. I need to connect 2 of these wires to the red and black on the radio cable to let the plotter send GPS coordinates to the radio, but I don't know which 2 wires to connect. I did some voltage testing and found that the red and black seem to be +12V and ground, respectively. The red and white show 1.5V to each other, as do the red and green. Green and black show a very small voltage. Red and black show 11.5. All voltages were measured while the plotter was set to output NMEA 0183.

My question is, which wires do I connect to the Cobra plug red and black wires? On the radio cable, the red is the NMEA in, and the black is the NMEA out. I don't know which wires to connect to on the bare wire NMEA cable out from the rig as described above and as shown in the pictures. I tried red radio to green plotter wire and black radio to white plotter wire, but that doesn't seem to work (although I didn't verify that the baud rate settings were the same on both the radio and the plotter).

Does anyone have any guidance here? It would sure be appreciated. Thank you!

Picture of the bare wire attached. Red and black pins are closer to the indent and white and green are on the other side.

[Trout Bum]

For starters the NON HS antenna puts out a 4800 baud rate. The radio must accept this baud rate. The HS antenna has a higher baud rate.

The wire colors straight out of the antenna pigtail according to the Humminbird GPS antenna manual are as follows:

Black = ground

Green = Antenna GPS Nmea out (connect to this wire if your device can only read GP Nmea sentences) This is the one that worked for me.

White = Control Head Nmea out (connect this wire if your device reads Integrated Navigation commands)

I would guess you need the Black and Green. If it doesn't work switch the Black and Green. Make sure you have NMEA Output turned on in the menu selections on your 998 (Main Menu/Setup/Nmea Output, on or off)

[Humminbird_Greg]

Welcome to the Humminbird Side Imaging Forums jjmoney.

I would try what Trout Bum suggested but use only the NMEA pigtail wire for the GPS Receiver you have mounted and running now (not any wire connections to/from the older HB plotter.

[jjmoney]

Thanks for the replies Troutbum and Greg!

I tried every combination possible. I first tried with the bare wire cable plugged into the NMEA-COM tail of the spare cable, and the COM of the spare cable plugged into the ACCY COM tail of the new pigtail. No combination seemed to work. With every one, I gave it some time, and shut the radio off and on to be sure. Not sure how long it should take to pick up the signal.

That failing, I cut the spare pigtail on its ACCY COM tail, and exposed some bare wire. It was yellow, orange, red, and black I believe. No combination here seemed to work (I stayed away from the red in all cases, since it was generally +12V).

If I knew what voltage to look for or anything, that would help. I'm reasonably sure this connection should be possible, but I just couldn't seem to get it together.

If anyone has any ideas of which pins/wires I need to connect, I'd very much like to know. Otherwise I don't know if I will be able to get this functionality working.

[Humminbird_Greg]

jjmoney,
Is the Black wire from the Cobra radio NMEA Output or NMEA Ground?
Either the Green or White should be the NMEA Output (from the Humminbird) and would connect to the Red wire (NMEA Input) to the Cobra radio but there needs to be a ground return for the NMEA signal back to the Humminbird Receiver.

You did have the NMEA Output menu in the 998c Si unit turned on, right?

Make sure that all testing is done where the GPS Receiver can ‘see’ the GPS satellites.

Unless you have a digital oscilloscope you may not be able to measure the NMEA Output voltage.

Did you try using the AS-YC y-cable?  It has three connectors on it labelled: ACCY-COM, NMEA-COM, and COM.  It has Orange, Yellow, Red and Black wires in one of its cables.  It should not be needed for this connection.

[Trout Bum]

I read your radio manual. It does not list the baud rate. Maybe that's the problem??

However, it does say that the plug in pigtail for your radio has black=negative/ground and red=NEMA in leads.

I would connect the black wire to the black wire on the GPS puck and the red to the green wire on the puck. I suggest you go directly to these wires and do not use any adapter other than the radio connector.

[jjmoney]

Thanks for the comments, gents. Yes TroutBum, I had also noticed that it doesn't specify baud in the Cobra manual. I wondered about that.

To clarify the options available, I have made a quick and dirty drawing of the plug jacks etc. available that should help illustrate everything. It shows the 998's pigtail, the bare wire cable, and the spare pigtail.

[Humminbird_Greg]

We are trying to tell you that you do not need the HHGPS cable jjmoney.
Just connect straight from the GPS Receiver’s NMEA pigtail wire to the Cobra radio plug.

[Trout Bum]

Get rid of the "Accy Com Male" and go directly to the antenna pigtail wires.

[jjmoney]

Sorry if I'm being dense, guys (typical engineer, hey?), but I don't yet totally understand where I would patch in when comparing your recommendations - although you both seem to be saying the same thing. Are you meaning to cut the 998's antenna pigtail on the ACCY COM leg and patch directly to the red/orange/yellow/bare wires inside it? A sketch would help a lot.

GPS was good, I was getting a location the 998. NMEA output was turned on as well.

Thank you most kindly for your suggestions, it is much appreciated, and could mean a big safety/distress bonus for me and my family etc. since I mostly boat on a large and somewhat remote lake.

[Trout Bum]

Your close to right.

You need to cut the pigtail wire at a point between the antenna/puck and where the "Accy Com Male" is SPLICED/CONNECTED on to it. Cut as close to the"Accy Com Male" as possible so as to have the most wire length left for connection/splicing to the radio pigtail.

Then you should have the black, green and white wires that go directly into the antenna/puck. These are the original antenna/puck wires that came with the antenna and that the "Accy Com Male" was spliced/connected to.

These are the wires to connect directly to the radio pigtail.

Go to the Bird website and look up the GPS Receiver and GPS Receiver/Heading Sensor Manual, No. 531478-4_C
Look at pages 6 & 8

[Humminbird_Greg]

You should be able to get the NMEA Output from the second, shorter “NMEA pigtail” wire that comes out of the GPS Receiver’s connector.  See attached pdf file.

[jjmoney]

Aha! I don't have this cable. I had actually seen that picture before when researching this prior to posting about it.

I will try and track one of these down. Many thanks!

Do you know the part number of this cable? I will sniff around but a part number would be the bee's knees.

[Humminbird_Greg]

If you are using a Humminbird GPS Receiver, then that should be what the connector end on it looks like.  If you look on the drawing the upper cable states "This cable goes to the GPS Receiver", this is the 20-foot cable from the GPS Receiver to its connector that plugs into the unit.

[jjmoney]

Nope, mine does not look like this. That's what the confusion was on my end. The only place I ever saw any other kind of wye or anything was a short leg of the cable with a black plastic cap on the end, it sort of looked like an antenna if I recall correctly. Perhaps there are bare wires under the small cap?

[Humminbird_Greg]

That's the NMEA pigtail!
I replied to your e-mail with a marked up picture.
Uncap that antennae looking wire and connect up to the Green and Black wires.

[jjmoney]

The mystery is solved. Will do. Stay tuned!

[Trout Bum]

If you look at page 8 in the manual I referenced above, it shows the capped pigtail and that the NEMA output comes from it.

[jjmoney]

Yes, it's all very clear now. I was so fixated on the plug-ended y cable that plugs into the head, that I completely overlooked the existence of the other real pigtail with the black end.

 Thanks to the both of you. I'll let you know how I make out. I have some confidence that I can get it right now. Cheers!

[Trout Bum]

Glad you finally got it.

I thought you had spliced the y-cable onto the original NEMA pigtail, that's why I said to cut it off. However, you weren't even using the pigtail.

As long as your radio is the correct baud rate, you should good to go now.

[jjmoney]

It worked immediately. Thank you guys very much for steering me in the right direction. This site rules.