My student team is currently using a Ubiquiti Rocket M5 and AMO-5G13 antenna on the ground connected to a Ubiquiti Bullet BM5HP and Fat Shark antenna on our fixed-wing UAV. This link is used for sending commands to the camera system on a Raspberry Pi 2 onboard and transferring images from the plane to the ground.
In the past we were sending about 2 MB 12 megapixel JPGs every 5 seconds. Recently we have upgraded our camera and will be sending smaller images but more quickly (5 MP at 1-2 per second). Due to a limitation of the new camera's API on ARM we may not be able to convert raw image data to JPG onboard and may have to send uncompressed raw data to the ground (5 to 15 megabytes depending on bit depth). This will be up to a distance of 1.5 km line of sight.
In a very simple test we set up the link indoors with about 20 feet between the antennas and got an average of 5 MBps/40 Mbps using scp to transfer a 100 MB file between a laptop and the Raspberry Pi in either direction. The Pi has a high-speed microSD card. It seems like we should be able to get a lot more. The Bullet has a maximum configurable speed of 65 Mbps (why 100 advertised?) and the Rocket has a max of MCS 15 / 130.
If we only get 40 Mbps at a very short distance, then won't it be significantly less over a long distance? Or is the short distance test causing issues? How can we improve performance with the current antennas or by buying better antennas or other hardware?