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DIY NMEA Cable for Live GPS/Depth Data to PC or Laptop

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Jolly Roger:
Hi all,

recently I was trying to figure out how I can get NMEA data send out to my laptop.  The idea behind it is that I want to use my laptop and navigation software (Quo Vadis) for navigation on board of my boat. The laptop’s bigger screen and  the software's better maps of Lake Constance brought me to this.

I have HUMMINBIRD’s AS-PC2 PC connection cable and the pigtail of HUMMINBIRD’s AS GR50 GPS receiver, but I was reluctant to cut the NMEA COM connector off of my PC connection cable like suggested on HB’s website. As we all know, "things" happen and the cable might be needed in the future for lets say an update or maybe a new funny Start Up Screen for the unit. So cutting off the NMEA COM connector wasn't an option because once cut and connected on the boat, it would have to stay on the boat and I would have to buy another PC connection cable for home.

Tinkering around with an old RS232 cable looked good at first, but getting the masses of wires in the cable sorted out made me think twice about it: ---> Screw it!!

As it turned out, there was a female NMEA COM connector on the Y- cable that came with the GPS receiver which fits to the male NMEA COM connector of  the AS-PC2 cable. So I thought I can get a connection that would send NMEA data to my laptop, without destroying my precious AS-PC 2 cable and without messing around with a lot of wires of an old RS 232 cable.

After debating with the guys here (thanks Bob, Chuck, Gert, Greg and Hendrik (appearance in alphabetic order)) I decided to pimp the pigtail of my GPS receiver and went to my workshop to give it a try.
Now here's what I did,
The following procedure makes you attempt to connect electrical wires with each other. This requires at least some advanced craftsmanship and special sophisticated tools!

What you need:
1.   GPS receiver's pigtail
2.   Y-cable
3.   Fine tipped Soldering iron with solder and solder fat
4.   Electrical insulation tape or electrical shrink tube / hot air gun
5.   Cutting pliers / Knife
6.   Ohm meter

Do not use these tools  ;D:

Use decent soldering equipment! But if you sport some colour blindness (med. "achromatopsia"), I suggest to leave the job to someone who recognizes colours and knows what he's doing. Same is true if you're not a soldering specialist: Unqualified messing around with hot tools may result in burning down your house / flat. I heard rumours that this might upset or annoy your mom / dad / landlord / neighbour or other people.

Another thing: Insulation!
Do not connect the cables to your unit / PC / laptop while working on them. Shorting the circuits and burning them through is something electronics don't like. And this isn't a rumour!
Use an Ohm meter to check for continuity, resistance and shorting.  Write down the measures for later reference and DOUBLECHECK!. Having your 1000 $ + equipment smoked is neither a good joke nor is it covered by HB'S warranty.

Talking about insulation:
Make sure you're using ELECTRICAL insulation tape or insulating shrink tubes in the right diameter. Some regular tapes do not insulate and this will lead to shortcuts. If you're taping, use some industrial alcohol or break disk cleaner  to clean the soldered parts before starting to tape. Some solder contains solder fat. This fat makes it tricky to attach the tape.
Try to keep the tape under tension while wrapping it around the wires/cable to get a good hold and some water protection. While keeping the tape under tension, keep in mind what Mickey Rourke told Don Johnson in the movie “Harley Davidson and the Marlboro Man” about pulling the trigger when Don Johnson shot his motorcycle: "Don't rip on it….!” These wires are tiny.

OK, enough of jokes and the pessimistic waffle now. Tool time!

Here's the first one of the candidates:

Get the cap off of the pigtail and carefully cut off the insulation. Be really careful and make sure you don't cut through the wire's insulation! Cutting through the wire's insulation might lead to a shorting. After removing the cable's insulation you'll see three wires: Red, Black and White.

We need the black and the white wire (Black is ground (-) and white is NMEA out from the GPS receiver). Here's where you can find pictures with the pin details for reference:;sa=album;in=15
Carefully cut off the insulation of the white and the black wire. Again: Be REALLY careful. These iron leads are no steel cables and they're easily cut through.

Next candidate: The Y-cable’s FEMALE connectors. Positively identify who is who here!

Cut off the FEMALE NMEA COM connector (that's the one with NMEA COM written on it and ONE cable going out / in). Carefully remove the insulation like above. Now here we have FOUR wires. We need the white wire and the BARE (silver) wire.

Now let's get ready for the hot part of our pimp show and heat up your soldering gear.
First solder the white wires together.

Next: Insulate the white wire BEFORE you solder the black / bare wires! It's easier to do this now, 'cause you can wrap the tape without having the black / bare wire in your way.

Next solder the black and the bare wire together and insulate them.

After this it's time to get the whole thing sealed. If you have shrink tubes and know how to handle them, use these. One thing I don't like about them shrink tubes is that sometimes they need a lot of heat to shrink and if one is not careful, the insulation of the wires might melt.
If you're using tape, wrap it twice around the cable before wrapping it around the wire.

This gives a better hold. Keep the red wire away from the others.


While keeping the tape under tension wrap it towards the other wires keeping the green wire in line with the cable.

Finish the whole procedure by holding the red wire opposite to the green wire. The more distance between the wires, the less chance to have a shortcut if things get tight.

Now we should have a pretty tight but still a bit flexible connection established and be ready to check if everything works as planned.


Use an Ohm meter for this and cross- and doublecheck!!

If everything 's fine: Now you're ready to go and you can use your AS-PC2 cable to output GPS signal or depth data to your PC or laptop!

I have put this project on the HB wish list. In my opinion it makes the GPS receiver's pigtail more versatile and user friendly. The pimped receivers pigtail will be a plug and play thing and it shouldn't be a big deal to get it done in the future.

As for now, I wish you good luck and success with your unit. If you have suggestions ---> shoot!

Regards / Harry


   ........ solder fat......................!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
on electrical connections. It wil cause corrosion.


Jolly Roger:
I know Hendrick,
but it cleans the metal parts and helps the solder to penetrate better. If you read further, I recommend to clean the parts after soldering  ;)

Regards / Harry

Ever try the liquid flux? Sure makes soldering a lot easier than using the old paste flux.


Need a little? From GC Electronics
Completely non-corrosive liquid solder flux consisting of a solution of special rosin in alcohol. Contains no traces of acids or chlorides and is completely safe to use on even the most delicate electronic equipment. For electronics applications
Check Other GC Chemicals  - [MSDS] [SPEC SHEET]

Jolly Roger:
Thanks for advice BENAMEN!
I hope I don't have to do any more soldering in the next weeks. Getting them tiny leads together was enough of fun for the moment. One needs at least two more hands to get them set and hold in place  ;D.

Regards / Harry


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