The MD77HR is a NMEA-based Compact Heading Repeater. Digital heading data (ship’s heading) may be conveniently displayed and monitored at any location on a vessel.


The MD77HR from MARINE DATA is a NMEA-based compact Heading Repeater. Digital heading data (ship’s heading) may be conveniently displayed and monitored at any location on a vessel.

When multiple heading sources are available in the heading data (e.g. True and Magnetic) the MD77HR allows the user to select the heading source and indicates which heading source is in current use.

Compact and rugged, the MD77HR offers a heading repeater solution for locations where the available space is limited and may be either bulkhead or panel mounted. Finished in jet black to complement other marine navigation equipment.

The MD77HR from MARINE DATA: flexible in application, easy to install and simple to maintain.


  • Main and Emergency power supplies; with monitoring of both
  • Dual NMEA inputs for two compasses shared on the same physical connector
  • Automatic selection and prioritisation of NMEA heading data type
  • Prioritisation of heading type: HDT (true), HDG (magnetic + variation), HDM (magnetic)
  • Automatic warning of loss of valid heading data and automatic detection of a previously lost heading data type without requiring a reset
  • Local and remote dimming control; Supply under-voltage warning



  • The MD77HR displays True or Magnetic Heading Data transmitted from marine equipment compatible with NMEA 0183 (IEC 61162-1) (Gyro compass, TMC, EMC, GPS Compass etc.)


  • Weight: 1.25 kg (on bracket)
  • Dimensions: H 166mm; W 200 mm; D 81mm Fascia 144 x 144 mm; Dial Ø 118 mm
  • Mounting: Bulkhead or panel mounted
  • Connections: 1x data cable to 15-pin D-sub plug
  • Construction: Aluminium alloy enclosure
  • Finish: RAL9005 Jet Black; fine texture paint


  • Power Supply: 24 V dc 4 W nominal (18-32 V dc)
  • Data Input: Digital RS422; NMEA 0183 protocol 4800 / 9600 / 19200 / 38000 Baud (auto-sensing)
  • Data Sentences: THS, HDT, HDG and HDM; detected on start‐up in descending order of priority
  • Cable: 2.5 m multicore data cable


  • Performance: ± 0.5° accuracy
  • Follow-up-rate: >20° per second
  • Display: Rotating compass card dial display
  • Dial Resolution: Scale marked at 1°, 5°, 10° & 45°
  • Dial Illumination: LED array with local & remote dimming control. Red tint
  • Alarm: Power supply failure: Audible and visible indications
  • Error Indication: Dial oscillates ±35° about the last known good heading. Dial illumination flashes
  • Heading Type: LED indicator for heading source type: Gyro Compass / Magnetic Compass
  • MTBF: 30,000 hours


  • IP Rating: IP54
  • Operating Temp: -15°C to +55°C
  • RoHS: Compliant
  • Compass: Safe Distance 100 cm


  • Conforms with: IEC 60945; IEC 62288; IEC 61162-1 ISO 8728; IMO Resolution A1021 (26)
  • Type Approval: Germanischer Lloyd (GL)


  • Supplied: Panel Mounting Kit
  • Option: Custom Paint Finish
  • Accessory: Bulkhead Mounting Bracket Kit

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