Icom M504 - User Manual

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Summary

Garmin GPS Connection

GPS Example Connections

Details on soldering wires and connecting GPS to the Icom radio, with a specific example for Garmin.

Standard Horizon GPS Connection

Troubleshooting GPS Connection

This document provides instructions for connecting a GPS device to Icom M504/M504A VHF radios and offers troubleshooting tips for GPS connections.

Function Description:

The primary function of this document is to guide users through the process of integrating a GPS receiver with an Icom M504 or M504A marine VHF radio. This integration allows the radio to receive crucial navigational data, such as latitude and longitude, from the GPS device. This is essential for features like DSC (Digital Selective Calling), which requires accurate position information for distress calls and other communication functions. The document details the specific wiring connections required for various GPS brands, including Garmin, Raymarine, and Standard Horizon, ensuring compatibility and proper data transfer. It also addresses common issues that may arise during the connection process and provides steps to diagnose and resolve them, thereby facilitating reliable operation of the combined system.

Important Technical Specifications:

The Icom M504/M504A radios are designed to interface with GPS devices using the NMEA 0183 standard. This standard defines how marine electronic devices communicate with each other. The radio's back panel provides two sets of wires for GPS connection:

NMEA IN (+): Typically a red wire, this input receives the "Data out" signal from the GPS.
NMEA IN (-): The shield of the red wire, this serves as the "Data ground" for the GPS output.
NMEA OUT (+): Typically a white wire, this output sends data to the "Data in" on the GPS.
NMEA OUT (-): The shield of the white wire, this serves as the "Data ground" for the GPS input.

The document specifies the NMEA sentences that the plotter/GPS receiver must be capable of sending for proper operation with the Icom radio. These include:

GPRMC (Recommended Minimum Specific GPS/Transit Data): Provides essential navigation data including time, date, position, speed, and course.
GPGGA (Global Positioning System Fix Data): Provides 3D location and accuracy data.
GPVTG (Track Made Good and Ground Speed): Provides information about the course and speed relative to the ground.
GPGLL (Geographic Position - Latitude/Longitude): Provides latitude and longitude, and optionally time of position fix and status.
GPGNS (GNSS Fix Data): Provides position, time, and fix type information from a Global Navigation Satellite System.

The GPS device must be configured to output these sentences via NMEA 0183. The document highlights that some Garmin models (172c, 182d, 152, 178d) may have specific wire color assignments for NMEA IN (+) (blue or green) and NMEA OUT (+) (brown or white). For Raymarine equipment, it's noted that direct connection to the GPS unit, rather than through a repeated port from other equipment like a plotter, might be necessary to ensure the correct NMEA sentences are passed to the radio.

Usage Features:

The document emphasizes the importance of correct wiring connections for seamless integration. Users are instructed to solder the GPS wires and their shields to the corresponding NMEA wires from the Icom radio. This ensures a secure and reliable electrical connection. The provided diagrams for Garmin, Raymarine, and Standard Horizon GPS units clearly illustrate the wire color codes and their respective connections to the Icom VHF radio's NMEA IN (+) / NMEA OUT (+) and NMEA IN (-) / NMEA OUT (-) terminals.

For Garmin GPS units, the connection is as follows:

Garmin Blue* (NMEA IN (+)) to Icom NMEA IN (+)
Garmin Brown* (NMEA OUT (+)) to Icom NMEA OUT (+)
Garmin Black (NMEA IN (-) and NMEA OUT (-)) to Icom NMEA IN (-) and NMEA OUT (-)

For Raymarine GPS units (models 420, 320, 425):

Raymarine White to Icom NMEA IN (+)
Raymarine Yellow to Icom NMEA OUT (+)
Raymarine Brown to Icom NMEA IN (-)
Raymarine Green to Icom NMEA OUT (-)

For Standard Horizon GPS units (models 155c/1000d, 175c):

Standard Horizon Blue to Icom NMEA IN (+)
Standard Horizon Brown to Icom NMEA OUT (+)
Standard Horizon Green to Icom NMEA IN (-) and NMEA OUT (-)

The document advises consulting the individual instruction manual from the GPS manufacturer for more specific information regarding their NMEA wiring.

Maintenance Features:

The document includes a "Troubleshooting Your GPS Connection" section, which serves as a guide for diagnosing and resolving common issues. This section outlines several key checks:

NMEA 0183 Sentence Capability: Verify that the plotter/GPS receiver is capable of sending the required NMEA 0183 sentences (GPRMC, GPGGA, GPVTG, GPGLL, or GPGNS). Users are advised to check their plotter/GPS instructions for this information.
Sentence Verification: Confirm that the plotter/GPS device is actively sending the necessary NMEA sentences.
Single Sentence Output: If latitude and longitude are still not being received, users can try configuring the plotter to send one NMEA sentence at a time (if possible). This can help identify the most compatible sentence for the Icom radio.
Professional Check: If issues persist, it is recommended to have a technician check the plotter/GPS using test equipment to verify that it is indeed sending the GPS sentence.
Solder Point Inspection: Users should carefully check the solder points on both the radio and plotter connectors. The document notes that some connectors are very small, which increases the likelihood of "solder bridging" (an unintended electrical connection between two points due to excess solder), which can disrupt data flow.

These troubleshooting steps are crucial for maintaining a reliable GPS connection, ensuring that the Icom M504/M504A radio always has access to accurate position data for safety and communication purposes. Regular verification of these settings and connections can prevent operational failures.