Radiomaster ER16 PWM Dual-Band Gemini/Gemini-X

RadioMaster ER16 PWM Dual-Band Gemini/Gemini-X is a 16-channel dual-band PWM receiver with full diversity for the ExpressLRS system on 2.4GHz and Sub-G 868MHz frequencies, suitable for large RC airplanes without a flight controller, where redundancy and a higher channel count are important. ExpressLRS is an advanced open-source RC system with long range, low latency, and a high refresh rate. This is the LBT (Listen Before Talk) version.

The receiver is based on two Semtech LR1121 radio chips and an ESP32-S3 processor. The receiver has full diversity (“true diversity”) — two antenna inputs and two radio chips. In Gemini-X mode, one chip receives on 2.4GHz and the other in the Sub-G 868MHz band, so the other maintains the connection if one band is interfered with. Each antenna connector has a permanently assigned band in this mode (ANT1 Sub-G, ANT2 2.4GHz), allowing the use of antennas tuned to a specific band. Telemetry power is up to 100mW and is configured via the LUA script.

16 PWM channels are available on the top side of the enclosure, simplifying wiring in a large fuselage. The PWM outputs are amplified to maintain signal quality even with long servo extension cables and reliably control large high-torque servos. In addition to PWM, the receiver offers a CRSF or SBUS serial output and a separate locking 4-pin JST-GH UART/CRSF port for connecting a stabilizer, flight controller, or telemetry sensors. The injection-molded durable plastic housing has straight sides for easy mounting and measures 61.5x43.8x16.8mm.

Power is supplied through two mutually isolated XT30 inputs for two independent batteries. If one power source fails, the receiver continues operating on the other without interruption, while the isolation prevents backfeeding between batteries. Telemetry monitors the voltage of up to four sources simultaneously — receiver and servo power (up to 12V), both XT30 inputs (up to 12V), and via the EXT-V connector, the main battery in the 4-70V range. The SW port is intended for a safety switch — as long as the key is inserted, the receiver remains off when powered via XT30. The switch is included, along with a fuselage mounting kit. Settings and firmware updates are performed via Wi-Fi and WebUI without removing the receiver from the model.

Important notice: The XT30 inputs supply battery voltage directly to the servo power rail. When powered by a 2S LiPo/Li-ion battery, HV servos must be used; standard 5V servos must be powered through a regulated 5V supply. When powering via XT30, the 5V/BEC wire from the ESC must be disconnected, otherwise backfeeding and damage may occur.