I bought a Xiaomi Mi 4k drone recently and have been wondering how I might extend the signal range. There are parabolic antenna boosters for the Phantom drones that don't quite fit right, but at $3 I decided to see if they could be modified, and to see if it made any difference in range.
After carving the holes for the antenna out, I slipped the parabolic reflectors on and launched the drone. It has a max speed around 35 MPH, but I headed East at 20 MPH. Flying over farm fields, my plan was to go until I lost signal (drone automatically returns when signal is lost), or until the battery hit 60%. At 60% battery, I was at a distance of 10,600 ft, but decided to keep going for 11,000 ft. Finally at 3.8 miles away and 56% battery remaining, I turned around and headed for home. The drone must have been fighting a headwind as the battery wore down faster on the return. At 2 miles out, I got a low battery warning. At 1.25 miles out the drone started fighting the controls to automatically land with 15% battery remaining. Finally, realizing that there was no way to make it home, I positioned the drone over a flat empty patch of grass and let it auto-land, touching down at an indicated 0% battery remaining and 30 minutes elapsed flight time.
I only had to go 0.8 miles to retrieve the drone, but it got me wondering what the most efficient speed would be to cover distance. It takes a certain relatively constant amount of power just to maintain altitude, but then it takes extra power to overcome drag.
Anyone have a guess as to what the most efficient speed to cover distance is? The drone travels at 19 MPH when automatically returning home, so I just figured this is close to the most efficient speed.
As to the $3 antenna booster; it worked incredibly well, doubling the stock range. Great proof of concept that a directional antenna can massively boost the range of a 5 GHz (or any frequency) signal.