The Garmin GSD 28 is an advanced external sonar module for Garmin GPSMAP 8000 and 9000 series displays, plus listed GPSMAP 7×3, 9×3, and 12×3 units. RapidReturn high-definition sonar, dual-channel CHIRP, and xCHIRP target separation give the module a broad operating range from 25-250kHz. The transducer is not included, so the sounder should be matched to the boat and fishing depth.

Output ranges from 300W to 3kW depending on the selected transducer, giving the installer a wide performance range. Dual low, medium, and high CHIRP channels allow different frequency combinations, while the Garmin network links the GSD 28 to compatible chartplotters. It is not a display, chartplotter, or complete fishfinder package. Power, Ethernet, transducer selection, and network compatibility should be planned together before installation.

Key Features

- RapidReturn high-definition sonar – Provides Garmin’s listed high-definition sounder processing.
- 300W to 3kW output – Lets the installation match sounder power to the transducer.
- Dual-channel CHIRP – Supports low, medium, and high frequency channel combinations.
- 25-250kHz frequency range – Provides broad frequency flexibility for different water depths.
- xCHIRP technology – Helps improve target separation in compatible sonar conditions.

Who Is This For?

This Garmin external sonar module suits offshore fishing boats, cruisers, and Garmin glass helm installations that need more sonar capability than a display alone provides. It is not ideal for buyers without a compatible Garmin display or transducer, because the GSD 28 is a module rather than a standalone fishfinder.

Compatibility

Confirmed compatibility includes GPSMAP 8000/9000 series, GPSMAP 7×3, 9×3, and 12×3 displays, dual-channel CHIRP, Garmin networking, and compatible transducers. The supplied information does not identify specific transducer models, NMEA 2000, NMEA 0183, radar, autopilot, Raymarine, Simrad, or Lowrance compatibility. No named incompatible system was provided.

Technical Specifications

- Brand: Garmin
- Model: GSD 28, 010-02613-00
- Technology: RapidReturn high-definition sonar
- Power output: 300W to 3kW, transducer dependent
- Channels: Dual-channel CHIRP
- Frequency range: 25-250kHz
- Feature: xCHIRP target separation
- Compatibility: GPSMAP 8000/9000, 7×3, 9×3, 12×3
- Transducer: Not included
- Warranty: 2-year limited warranty

Warranty & Support

Garmin provides a 2-year limited warranty. The supplied specifications do not state warranty exclusions or service procedures.

The GSD 28 is the Garmin choice when an existing display needs a serious external sounder rather than a basic internal sonar channel. Its trade-off is the separate transducer and installation work, but the 300W-to-3kW range gives the boat room to grow. Choose it for a planned Garmin network, not as an independent fishfinder.