$50 radio 5km out to sea?!!

Yes, but not really practical past 4km. Gear used: FS-i6X radio (Banggood): https://goo.gl/LB1vs6 Telemetry radios (Banggood): https://goo.gl/Y1PwKS VTX antenna (Banggood): https://goo.gl/uas4WC VTX (Banggood): https://goo.gl/WE1Dc6 GPS module (Banggood): https://goo.gl/V4HAN1 Helical antenna (Banggood): https://goo.gl/QMkTWz (ymmv...) FPV monitor (Banggood): https://goo.gl/Kv4VQ5 LiPo battery (HobbyKing): https://goo.gl/9WwdKK Mini-talon plane (Banggood): https://goo.gl/LHtd5r The 900MHz antenna on the ground station is one that I got with the u-blox RTK development set, I don't know where you can buy them. The 900MHz antenna on the plane is this, but seems to be discontinued (HobbyKing): https://goo.gl/HB7jK5