1. Please make sure the GND on VTx and Split is corrected connected:
2. Power your Split via USB with the TV-out cable and get live feed via this cable：
3. Solder one or several low ESR capacitors (making sure it reaches 1500-2000uF）to the board as shown below:
4. Change to another VTx. Some VTxs can create noises.
5. Change to another PDB. Some PDBs cannot supply clean power output.
6. Add an insulating mat between the mount of the Split Mini and the frame
Please check the link for reference: https://www.rcgroups.com/forums/showpost.php?p=38034969&postcount=543.You may also insulate the antenna which is conductive form the frame.