@Joseph Lopez good question — and honestly the right one to be asking before you commit to a deployment architecture.
The 50km figure is the drone-to-drone spec, meaning both modules are airborne with line-of-sight and zero ground reflection losses eating into the link. That's the best-case geometry you can get — elevated platforms, clear Fresnel zone, no multipath. The onboard antenna is what's being used in those tests, not external Yagis, so it's not a "we cheated with directional hardware" number, but it is very much an elevation-dependent number.
The reason ground-to-ground drops to 5km isn't the hardware changing — it's the link budget getting hammered by ground reflections, near-earth multipath, and the fact that your Fresnel zone is partially obstructed the moment you're at human height over typical terrain. The 15-20km man-to-drone middle ground is basically showing you that one elevated end recovers a lot of that margin.
So for your telemetry project it really comes down to deployment geometry — if one end is on a UAV and the other is a ground station, you're in that 15-20km envelope with the stock antenna, which is already solid. If you're ground-to-ground and need more than 5km, that's where adding a directional antenna on the fixed base station end would get you back toward that higher range figure without touching the airborne side.
