3DRobotics 915MHz 500mW Radio Telemetry Kit for PX4, APM, and Pixhawk Flight Controllers - SiK Firmware, FHSS, MAVLink, and Multi-Kilometre Range for UAV Ground Station Communication
The 3DRobotics 915MHz 500mW Radio Telemetry Kit is a 2-way half-duplex wireless telemetry system designed for UAV ground-station communication between APM, PX4, and Pixhawk flight controllers and a ground-side mission-planning computer running APM Mission Planner or compatible GCS software. The kit consists of 2 radios - a TTL serial board for the air-side flight controller connection and a USB radio for the ground-side laptop or tablet - both pre-programmed at the correct baud rate for direct connection to the flight controller and ground station without manual configuration, allowing immediate PID tuning, parameter adjustment, and real-time telemetry monitoring over the 915MHz link from first connection. The radio pair is based on HopeRF HM-TRP data link modules running custom SiK open-source firmware that substantially extends the capabilities of the underlying module, adding frequency hopping spread spectrum, adaptive time division multiplexing, MAVLink protocol framing, and a built-in error correcting code capable of recovering up to 25% data bit errors without retransmission.
Transmit power reaches up to 27dBm (500mW) with receiver sensitivity to -118dBm, delivering a demonstrated multi-kilometre range with a small omnidirectional antenna under typical open-field UAV operating conditions. The combination of frequency hopping spread spectrum and adaptive time division multiplexing improves resilience against narrowband interference and co-channel contention in RF-congested flying environments, while Listen Before Talk and Adaptive Frequency Agility further reduce collision probability on shared spectrum. Air data rates reach up to 250kbps on a transparent serial link that passes MAVLink telemetry packets between the flight controller and GCS without protocol conversion on the host side. The SiK firmware bootloader permits over-the-air radio firmware upgrades through the serial interface, and both AT commands for local radio configuration and RT commands for remote radio configuration of the air-side unit from the ground station are supported. Adaptive flow control, when paired with APM flight controllers, prevents serial buffer overrun under high telemetry data rate conditions. At under 4 grams without antenna, the air-side radio imposes minimal weight penalty on multirotor and fixed-wing UAV platforms.
Key Features
- Frequency: 915MHz ISM band for long-range UAV telemetry in regions where 915MHz operation is permitted
- Transmit Power: Up to 27dBm (500mW) for extended ground-to-air telemetry range
- Receiver Sensitivity: -118dBm for reliable signal reception at extended range with small omnidirectional antennas
- Pre-Programmed: Factory pre-configured at the correct baud rate for direct APM, PX4, and Pixhawk flight controller connection without manual setup
- 2-Way Half-Duplex: Bidirectional wireless communication between air-side TTL serial radio and ground-side USB radio
- Transparent Serial Link: Passes MAVLink telemetry packets without protocol conversion, directly compatible with APM Mission Planner and MAVLink-based GCS software
- Air Data Rate: Up to 250kbps for high-throughput real-time telemetry and parameter transfer
- MAVLink Protocol Framing: Native MAVLink framing and status reporting for direct APM, PX4, and Pixhawk telemetry stream compatibility
- Frequency Hopping Spread Spectrum: FHSS improves RF interference resilience and co-channel contention resistance in congested flying environments
- Adaptive Time Division Multiplexing: TDM optimises bidirectional channel sharing between air and ground radios under varying link conditions
- LBT and AFA Support: Listen Before Talk and Adaptive Frequency Agility further reduce RF collision probability on shared 915MHz spectrum
- Error Correcting Code: Built-in ECC recovers up to 25% data bit errors without retransmission for reliable telemetry under marginal link conditions
- Configurable Duty Cycle: Adjustable transmission duty cycle for regulatory compliance and co-existence with other 915MHz systems
- AT and RT Command Support: AT commands for local radio configuration and RT commands for remote air-side radio configuration from the ground station
- SiK Open-Source Firmware: Community-developed SiK firmware with bootloader supporting over-the-serial-interface firmware upgrades
- APM Adaptive Flow Control: Prevents serial buffer overrun under high telemetry data rate conditions when paired with APM flight controllers
- Bi-Directional Amplifier Compatible: Can be used with an external bi-directional amplifier for further range extension beyond the standard 500mW output
- Lightweight: Under 4 grams without antenna for minimal UAV payload weight penalty on the air-side unit
- Si1000 Microcontroller: Based on Silicon Laboratories' Si1000 sub-GHz RF microcontroller for integrated RF and processing in a single IC
Applications
- APM, PX4, and Pixhawk flight controller real-time telemetry and parameter monitoring via APM Mission Planner or compatible GCS software
- In-flight PID tuning and parameter adjustment over a multi-kilometre 915MHz wireless link without landing the UAV
- Fixed-wing and multirotor UAV ground station communication requiring pre-configured plug-and-play 915MHz telemetry
- Long-range UAV telemetry builds requiring FHSS interference resilience and up to 500mW transmit power
- MAVLink-based autopilot systems requiring transparent serial telemetry with native MAVLink framing and status reporting
- UAV range extension builds using the radio with an external bi-directional RF amplifier for beyond-line-of-sight telemetry distance
