Integrating VHF Radio With Your Fish Finder

A VHF marine radio and a fish finder with GPS are two of the most essential pieces of electronics on any boat. Connecting them together unlocks safety and navigation features that neither device offers alone — most importantly, the ability to transmit your exact GPS position in a distress call without manually reading and relaying coordinates during an emergency.

The integration also enables AIS (Automatic Identification System) display on your chartplotter, MOB (Man Overboard) alerts with GPS coordinates, and the ability to send your position to other vessels via DSC calls. This guide covers the two connection standards used for VHF-to-chartplotter integration, the wiring involved, and the setup process.

Why This Integration Matters

When you press the distress button on a VHF radio equipped with DSC (Digital Selective Calling), the radio broadcasts a digital signal on Channel 70 that includes your vessel identification (MMSI number), the nature of distress, and — if a GPS is connected — your exact position. Coast Guard stations and nearby vessels with DSC-equipped radios receive this alert with your coordinates displayed on screen.

Without GPS integration, the DSC call transmits your MMSI and distress type but no position. In a genuine emergency — taking on water, medical crisis, fire — the difference between a rescue team knowing exactly where you are and having to search for you can be life-or-death.

Every boater with a DSC-capable VHF radio (which is essentially every modern fixed-mount marine radio) should have GPS connected to it. If your fish finder or chartplotter has GPS, you already have the position source — the integration just needs to be wired.

Connection Standards

NMEA 0183

NMEA 0183 is the older, simpler standard. It uses a serial data connection — typically two or three wires — to pass GPS data from your fish finder to your VHF radio. One device is the "talker" (your GPS-equipped fish finder) and the other is the "listener" (your VHF radio).

Wiring is straightforward: connect the GPS output wires from your fish finder to the GPS input wires on your VHF radio. Your fish finder's documentation will identify the NMEA 0183 output wires by color (often yellow/green or brown/green). Your VHF radio's documentation identifies its NMEA 0183 input wires. Connect talker positive to listener positive, talker negative to listener negative, and optionally connect the ground/shield wires.

NMEA 0183 is a one-to-one connection — one talker, one listener per wire pair. If you want to share GPS data with multiple devices, you'll need a NMEA 0183 multiplexer or repeater.

NMEA 2000

NMEA 2000 is the modern networking standard used by most current marine electronics. It uses a backbone cable with standardized drop connections, allowing multiple devices to share data on a single network. Any device on the NMEA 2000 network can see data from any other device — GPS from the chartplotter, engine data from the motor, depth from the transducer, wind from a sensor.

If both your fish finder and VHF radio have NMEA 2000 ports, connecting them is often as simple as adding a T-connector and drop cable to your existing NMEA 2000 backbone. The devices auto-detect each other and begin sharing data. No manual wire-to-wire connections, no talker/listener configuration.

The NMEA 2000 approach is particularly clean on boats with multiple electronics — the backbone carries all data, and adding a new device is a plug-and-play process. For a deep dive into NMEA 2000 networking, see our fish finder networking guide.

Setting Up DSC

Once your VHF radio is receiving GPS data from your chartplotter, you need to register for and program your MMSI (Maritime Mobile Service Identity) number. In the United States, recreational boaters can register for a free MMSI through BoatUS or the FCC. The 9-digit MMSI number is programmed into your VHF radio and identifies your vessel in DSC communications.

After programming the MMSI, test the GPS feed by checking the VHF radio's display — it should show your current coordinates updating in real time. Most radios display a GPS icon when they're receiving valid position data. If the coordinates aren't appearing, verify the wiring connections and check that your fish finder's NMEA output is enabled in its settings (it's sometimes off by default).

AIS Display on Your Chartplotter

If your VHF radio includes AIS receive capability (many mid-range and higher models do), vessels transmitting AIS appear as targets on your chartplotter's map display. Each target shows the vessel's name, speed, heading, and closest point of approach (CPA). This situational awareness is valuable in busy waterways, reduced visibility, and night operations.

AIS data passes from the VHF radio to the chartplotter via the same NMEA 0183 or NMEA 2000 connection that carries GPS data. On most chartplotters, AIS overlay is enabled in the chart display settings — turn it on, and AIS targets appear as icons on your navigation chart.