Hi,
with 8dBi Flat Patch Antenna @ video-rx 10mW Video-tx (comtech and airwave) are good enough for >800m. More powerwful video-tx are forbidden in the most european countries as well as 1,2GHz.
2,4GHz RC and 2,4GHz Video won't work because of RC's frequency-hopping. France-mode @ Fasst works less or more and dependent on the selected video-tx frequency (channel).
Most(!) visual disturbances in video (ie. circular flights, antenna orientation) are at more powerful txs nearly the same.
In my experience over years following works fine:
- 2,4GHz video (10mW, Comtech, Airwave) with Flat Patch Antenna @ rx, 35MHz RC and 868MHz Telemetrie (Wi.232)
- 5,8 GHz video (25mW, Comtech) with Flat Patch Antenna @ rx, 2,4GHz RC (Jeti) and 868MHz Telemetrie (Wi.232)
Video-TX and camera never at ESC-battery!
It's very important to make all HF-cables as short as possible and without any connector(s). The antenna cable shielding must end as near as possible at the solder pad for HF-signal. HF is Voodoo