Very small size, light weight. 433Mhz frequency band. /  915Mhz frequency band Transparent serial link. Range of approx 1 mile with supplied aerial. Demonstrated range of several kilometers with a small omni aerial. Can be used with a bi-directional amplifier for even more range. MAVLink protocol framing and status reporting. Frequency hopping spread spectrum (FHSS). Adaptive time division multiplexing (TDM). Descriptions: Support for LBT and AFA. Configurable duty cycle. Built in error correcting code (can correct up to 25% data bit errors). Open source firmware. AT commands for radio configuration. RT commands for remote radio configuration. Adaptive flow control when used with APM. Based on the HopeRF HM-TRP radio module, featuring an SiLabs Si1000 RF microcontroller. 3DR Radio Telemetry Kit 433Mhz Module Open source for APM 2.5 2.6 2.8. The 3DR Radio is the ideal way to setup a telemetry connection between your APM and a ground station. Small, inexpensive and with great range, the 3DR radio uses an open source firmware which allows us to do things that cannot be done with other radios.  Specifications:     Item Name: 3DR Radio Telemetry Module Band: 433MHz  915MHz Receiver sensitivity: -117 dBm Air data rates: up to 250kbps Transmit power: up to 20dBm (100mW) Antenna connectors: RP-SMA connector Output Power: 100mW (20dBm), adjustable between 1-20dBm Interface: Standard TTL UART Connection status: LED indicators FPV Radio telemetry air module size: 50  x 27 x 10mm FPV Radio telemetry ground module size: 70 x 22 x 11mm Package size: 165 x 80 x 11mm Color: Black                                                                        Packing content:                  2 x Aerial 1 x Radio Telemetry Base Station (USB Connection) 1 x Telemetry Transceiver (Pin Header) 2 x Cable Set 1 x Connector