Microhard Systems P900 (OEM)

The P900 (OEM) from Microhard Systems (Canada) is a miniaturised serial mesh modem for 900 MHz with 1 W for long-range telemetry and control links, built for mid-size multicopters and other unmanned systems. It belongs to the manufacturer's Pico series. Unlike ExpressLRS or Crossfire receivers it has no servo outputs: it is a radio modem that carries serial data and can connect several participants in a mesh.

The modem operates in the band 902 to 928 MHz with link rates of 57.6 to 276 kbit/s. That is the data rate of a telemetry modem, not of a video system. Transmit power is adjustable from 100 mW to 1 W. The range of 60 km comes from the brochure (“40 miles”, 64 km by calculation, rounded by the manufacturer) and, without flight altitude, antennas and clear line of sight, is not comparable with other systems. The OEM board weighs 5 g at 26.5 x 33 x 3.5 mm and needs 3.3 V; the housed version at around 120 g takes 9 to 30 V.

The range 902 to 928 MHz is a US ISM band. In the EU it is not released as a whole; for links of this kind the range around 868 MHz applies there, with its own power and duty-cycle limits. Equipment may be operated in the EU only in the approved frequency ranges and power levels; whether and at what power the P900 is permitted in the country of use must be clarified before buying.

When choosing, remember that a modem always needs two ends, one on the ground and one in the air, each with a serial interface to the flight controller or computer. A mesh requires configuration of the network and its nodes. 900 MHz antennas are longer than 2.4 GHz antennas, and at 1 W the OEM board gets warm. Antenna and supply connectors are the wear points.