Holybro H-RTK ZED-F9P (RM3100 Compass)

The Holybro H-RTK ZED-F9P with RM3100 compass is an RTK rover with a u-blox ZED-F9P, an industrial RM3100 compass and a stacked dual-band patch antenna for medium-class multicopters. Chinese maker Holybro offers it in three versions depending on the connector, with UART or as a DroneCAN variant.

The receiver uses two bands (L1 and L2) and handles GPS, GLONASS, Galileo, BeiDou and QZSS. For RTK Holybro states 0.01 m + 1 ppm as CEP, horizontal and vertical, that is 1 cm at a radius containing half of the measurements, plus 1 mm per kilometre of distance from the base. The rate is at most 8 Hz in RTK operation, 20 Hz for raw data and 5 Hz in moving-base operation. NMEA, UBX and RTCM 3.3 are spoken. The DroneCAN variant additionally carries an STM32G4 processor and the ICM42688 and ICP20100 sensors; for the latter Holybro notes 'pending support', meaning firmware support still to come. The manufacturer states ingress protection IPX6, that is protection against powerful water jets. The unit weighs 117 g.

A stacked patch antenna consists of two elements one above the other, one per band, and needs a ground plane. The industrial RM3100 compass is less sensitive to interfering fields than simple sensors but still depends on distance from power leads. The EU classes apply to the aircraft: from C1 upward geo-awareness and remote ID are mandatory, both resting on the GNSS position, and at 117 g the unit counts noticeably towards take-off mass.

For selection the connection decides: UART for simple wiring, DroneCAN for several devices on one bus. 117 g belongs on a mast with a firm, low-vibration mount. Upkeep includes compass calibration after installation, firmware and a check of the connectors.