Acoustic Modems

Vexa Locator: USBL-Enabled Modem

Vexa Locator One signal — two answers

Vexa Locator is a hydroacoustic modem that communicates and locates the source, resolving the slant range and horizontal bearing of every incoming signal to 2° across an 85° cone. One device where other setups require two.

2°accuracyHorizontal bearing across an 85° cone
3000metresTwo-way data and positioning range
254addressesDevices on a single network
  • Two-way data link — the modem transmits and receives digital data between underwater points up to 3000 metres apart
  • Positions by range and bearing — every incoming transmission yields slant range and horizontal angle of arrival, accurate to 2°, without a separate USBL head
  • Remote telemetry — a single request returns depth and temperature from any Vexa-family unit
  • Remote control — it issues preset commands to a remote instrument
  • 85° working cone, 2° bearing accuracy — a true horizontal reading, whatever the mounting angle
  • 2-axis pitch/roll inclinometer — corrects for the unit's own tilt
  • Compact form factor: Ø64×128 mm, 440 g — suitable for ROV and diver deployment
  • Depth rating 300 m — sufficient for most inspection and survey work
  • 20 code channels, 254 subscribers — shared protocol across every Vexa deployment
  • Open, documented protocol — NMEA-style, shared libraries across the Vexa family

Most acoustic modems send data. Vexa Locator sends data and resolves where it came from, so the surface operator gets the message and its position in the same transmission. A phased array and a built-in inclinometer read the slant range and horizontal bearing of every incoming signal, to 2 degrees across an 85-degree cone — riding the same 3000-metre link that carries the data. Query any Vexa-family unit in range for its own depth and temperature over that same connection, which wires straight into the vehicle's control system. One unit. Two jobs. Every time.

Vexa Locator
Ships as a single, ready-to-integrate unit — no separate USBL head or transceiver required alongside the modem. Runs the same CDMA-style code-division as every other Vexa device — 20 channels, 254 subscribers. A 0.5 m, 5 mm UART cable at 9600 bit/s wires it directly into the host control system or vehicle.
Full specifications (PDF, 196 KB)

Performance

Working angle (cone, from horizontal) 85°
Horizontal AoA accuracy (typ.) 2°

Acoustics

Operating range 3000 m
Payload data rate 78 / 156 / 314 / 634 bit/s
Bit error rate 10⁻⁶
SNR −2 dB
Max. relative velocity ±1 m/s
Carrier frequency 20050 Hz
Max. acoustic source level (in-band) 175 dB re 1 µPa @ 1 m

Electrical

Supply voltage 5 – 12 V
Data lines voltage 0 – 3.3 V
Data lines output impedance 1 kOhm
Rated startup time 100 ms
Power consumption (Rx / Tx) 0.33 W / 15 W

Interface

Interface UART 9600 bit/s
Communication protocol NMEA 0183 PUWV
Subscribers division Up to 20 code channels
Packet mode 254 addresses, broadcast, up to 64 bytes/packet

Mechanical

Dimensions (Ø × h) 64 × 128 mm
Weight (dry) 0.44 kg
Cable length / diameter 0.5 m / 5 mm

Environment

Operating depth 300 m
Working temperature −5 … +50 °C

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