Pilots use remote control radios to send signals to a drone to control it. They also receive information back from the same drone. This feature is referred to as telemetry and since it provides the pilot with real-time information about things which one cannot know from just looking at the drone, like the battery status, it is important.
Telemetry links usually provide low bandwidth and are not suitable for massive data volumes as those needed for a real-time video feed from a drone camera.
Two relevant topics with radio equipment are reliability and legality. Reliability is about the quality of the equipment used, but also about the frequencies used and about the strength at which signals are broadcast. This is also where legality comes into play, since different countries have different laws about frequencies that can be used and the allowed broadcast signal strength. Long-range radio equipment ordered over the internet from a foreign country might be in conflict with local laws.
Reliability of radio communications is also impacted strongly by where antennas are placed, on the drone and on the ground.
Reliability of radio communications is also impacted by electrical interference. Increased electrical interference can be an unintended consequence of modifications made to drones. This is another reason why careful testing is needed after all modifications, since a loss of radio control can have severe consequences.
- Accidents caused by signal loss.
- Illegally operated radio equipment causes disturbances to manned air traffic or other users of the same frequencies.
- Fines and disruption of operations due to the use of restricted frequencies.
- Interview pilots and flightcrew members about loss-of-control incidents due to problems with radio links. Signal loss occurs also with distance and can be an indication that drones were flown beyond the visible line of sight required by law.
- Verify that the frequency and wattage of all equipment is within the legal range of such equipment as per local laws.
- Verify that permits for radio equipment operation have been obtained if so required by local laws.