with a flight controller that supports Smartaudio or Tramp Happymodel OVX300 and OVX303 VTX are based on the Open source project OpenVTX powered by JyeSmith (EpxressLRS team) OpenVTx aims to provide firmware with both the SmartAudio and Tramp protocols. Either protocol can be used on the flight controller and on VTx power up the protocol used is automatically detected by OpenVTx. Currently SA is fully implemented and test against Rev. 09. To date IMRC has not released a protocol standard and implementation is based on information found within Betaflight. More info and community https://github.com/OpenVTx/OpenVTx https://discord.gg/uGUKaD2u8Z OVX303 Specifications Model: OVX303 Frequency: 5.8G 40CH Transmitting Power: 0/RCE/25mw/100mw/300mw Power supply: DC 5V Current (5v): lt;650ma (300mw) Weight: 1.5gram without antenna