Radiomaster ER12 PWM Dual-Band Gemini/Gemini-X

RadioMaster ER12 PWM Dual-Band Gemini/Gemini-X is a 12-channel full diversity PWM receiver for the ExpressLRS system on 2.4GHz and 868MHz frequencies, suitable for larger RC aircraft with a higher number of servos. The receiver offers 12 amplified PWM outputs, a dedicated XT30 power input, and telemetry voltage measurement.

The receiver is built around two Semtech LR1121 chips and supports both Gemini and Gemini-X modes. It features full diversity (“true diversity”) — two antennas and two radio chips, ensuring a stable connection in various environments. In Gemini-X mode, one chip receives on 2.4GHz and the other on the Sub-G 868MHz band; each antenna connector is assigned to a specific band (A1 = Sub-G 868MHz, A2 = 2.4GHz), allowing tuned or directional antennas to be used for each band separately. Telemetry power is up to 100mW (adjustable via LUA script). The antennas connect via durable MMCX connectors, and the package includes two pairs of 25cm antennas — 2x 2.4GHz and 2x dual-band, allowing the set to be selected according to the mode used. The antennas should be positioned perpendicular to each other and away from metal and carbon parts of the model. The receiver is compatible with all ELRS transmitters and modules, including radios with integrated ELRS.

The PWM outputs are amplified, helping maintain a clean control signal even with long servo leads and extension cables, while improving compatibility with large high-torque servos. The receiver is powered within a 5-12V range via servo pins or through the XT30 connector, which supplies power directly to the servo power rail for more demanding setups. Three independent ADC channels measure voltage at the EXT-V input (flight battery, 4-70V, 2-pin JST-GH), receiver power supply (V-PWM, up to 12V), and XT30 input voltage (up to 12V). The locking serial 4-pin JST-GH UART port provides CRSF or SBUS output and is also used to connect telemetry ERS sensors. Settings and firmware updates are performed via Wi-Fi and WebUI without removing the receiver from the model. The injection-molded plastic housing has flat sides for easy mounting, measures 51x37.6x14.5mm, and weighs 22.5g without antennas.

Important notice: The XT30 input supplies battery voltage directly to the servo power pins — output voltage matches the input voltage. Only servos rated for the connected voltage must be used; when powering from a 2S LiPo/Li-ion battery, HV servos are required. Standard 5V servos must be powered via a regulated 5V supply or through the standard power pins. When powering via XT30, the ESC's 5V/BEC wire must be disconnected, otherwise backfeeding and damage may occur.

The receiver is supplied in the LBT version for the EU.