Drones are less expensive to fly than planes or helicopters and can be a valuable tool for tower inspections, experts told attendees at the IEEE Broadcast Symposium in the Washington, D.C. area Thursday. By using a drone, you “can collect measurements quickly,” said John Kean of Cavell Mertz & Associates. Drones can measure signals at regular intervals, along with location and altitude in elevation measurements. An FAA waiver is usually required to fly at tower height and getting that permission can take as long as three months, he said.
Since a drone’s battery life is typically 20 to 30 minutes, a pilot has to segment the flights and piece together the results. Measurements can be obtained by spending only a few hours on-site. Commercial drones require an FAA-certified pilot. An engineer studies the tower and determines the proper flight distances.
Ian Gair of Sixarms says his company’s drones include an integrated spectrum analyzer on-board. Using a pre-determined flight path, the drone flies with an antenna pointed towards the tower.
The flight software discards invalid data (caused by excessive yaw and pitch, for example) and gives preliminary live results to the operator via a link to the ground station. Describing some antenna problems diagnosed by drone, Gair cited antenna feed lines cut to the wrong length, mechanical lean from storm damage and incorrectly installed antennas. Drones have also helped station engineers diagnose the effects of adjacent towers on their signal. In one case, measurements from the drone showed a notch in the antenna array pattern.
October 16, 2017