VTX stands for video transmitter, it's an essential part of an FPV system. It's a device that sends the video from an FPV camera to a video receiver, which can then display it on a monitor or FPV Goggles. Video transmitter connected to an FPV camera.
AKK FX2-ultimate-mini VTX(US Version), 1000mW with all legal frequency consistent with FCC Regulations
The Runcam TX200 is a backpack stlye analog VTX that is small in size but packs a lot of power.