Garmin GPS 120 Manual

The Garmin GPS 120 is a rugged, waterproof marine GPS receiver designed for navigation on the water. It features a high-sensitivity GPS receiver, simple interface with dedicated keys, waypoint and route storage, track plotting, and NMEA 0183 output for connection to autopilots or chartplotters. Below are key sections for safety, features, installation, setup, operation, and troubleshooting.

Features at a Glance

Key components: Waterproof case, backlit LCD display, dedicated navigation keys, external antenna connector, power/data cable port.

Feature	Description
GPS Receiver	High-sensitivity, 12 parallel channel
Display	Backlit LCD, 4-line text
Waypoints	Store up to 500 with names and symbols
Routes	Create and store up to 20 reversible routes
Tracks	Plot and save track logs
NMEA 0183 Output	Interface with autopilots, chartplotters
Waterproof Rating	IPX7 (submersible to 1 meter for 30 min)
Power Input	10-40 VDC, typical 12V marine system
Backlight	Adjustable for night use
Mounting	Includes bracket for fixed or swivel mount

Installation

Unpack and inspect contents. Choose mounting location with clear view of sky.

1. Mount unit: Use provided bracket; secure to dash or console.
2. Connect power: Red wire to positive (+), black wire to negative (-) on 12V system.
3. Connect antenna: Attach external GPS antenna if required for better reception.
4. Connect NMEA devices: Wire NMEA output to autopilot or chartplotter input.

WARNING! Ensure power is off during installation. Use appropriate gauge wire for power connections.

First-Time Setup

Power on unit; acquire satellite signal.

1. Initialization: Unit will search for satellites; may take several minutes first time.
2. Set location: If prompted, enter approximate position to speed acquisition.
3. Set preferences: Use MENU to set units (nautical miles, knots), time format, north reference.
4. Calibrate compass (if applicable): Follow on-screen prompts.

CAUTION! Ensure antenna has clear view of sky for best GPS performance.

Specifications

• GPS Channels: 12 parallel channel receiver.
• Accuracy: Position: <15 meters, Velocity: 0.1 knot.
• Update Rate: 1 second continuous.
• Waypoints: 500 user waypoints.
• Routes: 20 routes with up to 50 waypoints each.
• Track Log: 10,000 points.
• Interface: NMEA 0183 v2.0 output.
• Power: 10-40 VDC, 1 watt typical.
• Display: 4-line x 16-character LCD with backlight.
• Operating Temp: -15°C to 70°C (5°F to 158°F).
• Waterproof: IPX7 standard.

Controls and Settings

Access functions via dedicated keys and MENU system. Front Panel: POWER, PAGE, ENTER, GOTO, MARK, arrow keys.

Key Functions: POWER: On/Off; PAGE: Cycle display screens; ENTER: Confirm selection; GOTO: Navigate to waypoint; MARK: Create waypoint at current position.

Settings Menu: Units (Distance, Speed, Elevation), Time (Format, Time Zone), System (Backlight, Contrast, Beeper), Navigation (CDI scale, north reference).

Connecting Devices

NMEA 0183: Connect to autopilot, chartplotter, or PC interface. Power: 12V marine system.

1. Turn off all devices before connecting.
2. Connect NMEA OUT wires to NMEA IN on receiving device.
3. Ensure proper polarity for power connections.
4. Use shielded cable for NMEA connections to reduce interference.

Tip: Refer to your autopilot or chartplotter manual for specific NMEA wiring details.

Navigation Basics

Primary screens: Position, Navigation, Highway, Plotter.

1. Position Screen: Shows coordinates, speed, heading, time.
2. Navigation Screen: Shows bearing, distance, cross-track error to destination.
3. Highway Screen: Graphical representation of course to steer.
4. Plotter Screen: Shows track and waypoints.
5. Go To: Press GOTO, select waypoint, ENTER to navigate.
6. Mark Position: Press MARK to save current location as waypoint.

WARNING! GPS is an aid to navigation. Always use in conjunction with proper charts and traditional navigation methods.

Waypoints & Routes

Create, edit, and navigate waypoints and routes.

1. Create Waypoint: Press MARK, edit name/symbol if desired, ENTER to save.
2. Edit Waypoint: MENU > Waypoints > select waypoint > Edit.
3. Create Route: MENU > Routes > New > Add waypoints in sequence.
4. Navigate Route: MENU > Routes > select route > Navigate.
5. Reverse Route: While navigating route, option to reverse.

Note: Waypoints can be organized by symbol for easy identification.

Care & Maintenance

Clean with fresh water and mild soap. Rinse after saltwater use.

CAUTION! Do not use harsh chemicals or abrasives. Ensure connectors are dry before connecting/disconnecting.

Regulatory Information

FCC Part 15: Class B digital device; complies with interference limits. This device complies with part 15 of the FCC Rules. Copyright © Garmin Ltd. or its subsidiaries. For support, visit www.garmin.com or contact Garmin Product Support.

Troubleshooting

Symptom	Possible Cause	Corrective Action
No power	Power connection	Check fuse, verify 12V at unit, ensure proper polarity.
No satellite acquisition	Antenna view, initialization	Ensure clear view of sky; allow several minutes for first fix.
Inaccurate position	Poor satellite geometry	Wait for better satellite coverage; ensure no obstructions.
NMEA not working	Wiring, settings	Check connections; verify NMEA output is enabled in settings.
Display dim	Backlight setting	Adjust backlight level in System settings.

Reset: Power off/on. For persistent issues, perform master reset (see advanced manual).

Service: Contact Garmin Product Support or authorized service center.