Connecting a handheld GPS to a Marine VHF radio

Explains how a connected a low cost handheld GPS to a low cost (on sale) VHF marine radio. This supports DSC (digital selective calling) and automated distress calls.

(I'll upload some photos of this tonight)
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Step 1: The parts I started with

The VHF radio - I picked this up new, at a really good price due to a sale. In the process I also learned that it can be connected to a GPS and learned how the automated distress signal works. I also learned that with DSC it can send position info to other boats.
(note: at the time of purchase, I didn't know it could work with my handheld GPS)
The ETrex GPS - really cheap haldheld unit that has served well over the last couple of years.
DB9 Serial Connector - from an old computer. You should be able to find this at your local electronics shack.

Step 2: Figure out if it can work

The manual for the radio states that accessories need to implement the NMEA 0183 standard (I later learned what this is).
A google search for NMEA and ETrex shows a site listing GPS units that support the standard. Mine is listed, woohoo.
I later discovered that in the setup menu in the GPS, its a communication option (I should have checked the device first).

Step 3: Wire things up

I hooked up the serial interface cable to the GPS, next, I googled for the pin diagram.
It shows serial communication from pin 2 or 3 and the ground on pin 5.
I fire up the radio and the GPS.
I just stick the bare ground in the number 5 hole in the serial connector, and the other wire in the pin 2, nothing happens. Move it to pin three, a few seconds later, life. Woohoo.