AirMar B75H Chirp Depth Sounder

Overview

The AirMar B75H Chirp Depth Sounder is a high-frequency, single-beam broadband echosounder engineered for precision bathymetric profiling and fish-target discrimination in marine environments. Utilizing patented Chirp (Compressed High-Intensity Radar Pulse) signal processing, the B75H transmits a swept-frequency pulse across a continuous 80 kHz bandwidth (130–210 kHz), enabling superior range resolution and signal-to-noise ratio compared to conventional fixed-frequency sonars. Unlike traditional pulsed echo sounders, Chirp technology maintains constant acoustic energy over time while varying frequency—resulting in improved bottom detection at depths up to 3,000 meters and enhanced target separation of biological scatterers (e.g., baitfish schools vs. gamefish) and submerged structural features. The transducer’s low-profile through-hull mounting design minimizes hydrodynamic drag and preserves hull integrity, making it suitable for vessels up to 8 meters in length with fiberglass or wooden hulls.

Key Features

• Chirp broadband operation (130–210 kHz) delivering 5–10× higher resolution than standard 200 kHz fishfinders
• Integrated fast-response thermistor for simultaneous water temperature measurement
• Three tilt-angle configurations (0°, 12°, and 20°) to accommodate varying hull deadrise angles up to 24°
• Patented Xducer ID® technology enabling automatic transducer recognition and optimized parameter configuration within compatible chartplotters and multifunction displays
• Robust bronze housing with polyurethane acoustic window for corrosion resistance and optimal acoustic coupling
• Compact through-hull installation requiring only a 70 mm cutout and 95 mm shaft length
• 10-meter shielded, tinned-copper cable with NMEA 2000-compatible interface and built-in temperature sensor wiring

Sample Compatibility & Compliance

The B75H is designed for deployment on recreational and light-commercial vessels with non-metallic hulls (fiberglass or wood). Its acoustic performance is calibrated for seawater applications; freshwater use is supported but may require manual sound velocity compensation adjustments. The transducer complies with international marine electromagnetic compatibility standards (IEC 60945, EN 60945) and meets RoHS Directive 2011/65/EU requirements for hazardous substance restrictions. While not certified for safety-critical navigation under IMO SOLAS Chapter V, it supports auxiliary depth monitoring in accordance with IHO S-57 and S-100 hydrographic data models when integrated into compliant ECDIS or chartplotter ecosystems. No regulatory certification for underwater noise emission (e.g., ICES 2022-03) is claimed, though its narrow beamwidth and directional radiation pattern minimize lateral acoustic interference.

Software & Data Management

The B75H operates as a plug-and-play NMEA 2000 device, transmitting depth, water temperature, and raw Chirp return data via PGN 128267 (Depth Below Transducer) and proprietary vendor-specific PGNs for advanced echo log streaming. When paired with AirMar-compatible MFDs (e.g., Garmin GPSMAP, Raymarine Axiom, Furuno TZtouch), users access real-time spectral analysis, bottom hardness estimation, and split-screen overlay of CHIRP sonar returns with GPS position and heading. Firmware updates are performed via USB-connected PC using AirMar’s free Transducer Configuration Utility, which also enables user-defined frequency sweep profiles and gain calibration offsets. Audit-ready logging of transducer health metrics—including impedance diagnostics and temperature drift history—is available for GLP-aligned maintenance records.

Applications

• High-resolution bathymetric mapping for coastal survey support and habitat characterization
• Commercial and sport fishing operations requiring precise pelagic and demersal target identification
• Underwater infrastructure inspection (e.g., pilings, mooring systems, wreck localization)
• Scientific research involving zooplankton layer profiling and swim-bladder resonance analysis
• Integration into autonomous surface vehicle (ASV) platforms for uncrewed hydrographic missions
• Marina and harbor dredging management through repeatable depth change monitoring

FAQ

Is the B75H compatible with non-AirMar displays?
Yes—it adheres to NMEA 2000 standards and functions with any certified display supporting PGN 128267; however, advanced Chirp visualization and Xducer ID® features require vendor-specific firmware integration.
Can the B75H be installed on aluminum or steel hulls?
No—its acoustic design assumes low-attenuation hull materials. Installation on metal hulls requires a fairing block or external bracket mount, which is not supported by the manufacturer and voids warranty.
Does the B75H support dual-frequency or multi-beam operation?
No—it is strictly a single-beam Chirp transducer. Multi-frequency capability is provided by separate models (B75L, B75M) or the stainless-steel SS75 series variants.
What is the recommended maximum vessel speed for optimal bottom tracking?
For consistent 3,000 m depth detection, speeds should remain below 25 knots; above this threshold, cavitation-induced signal dropout may occur due to turbulence at the transducer face.
How often does the transducer require recalibration?
Factory calibration remains stable over the product lifetime under normal operating conditions; field recalibration is not user-accessible but diagnostic impedance checks can be performed annually via configuration software.