  With the Auger Engineering Radio Array (AERA) located at the Pierre Auger
Observatory, radio emission of extensive air showers is observed. To exploit
the physics potential of AERA, electric-field amplitude measurements with the
radio detector stations need to be well-calibrated on an absolute level. A
convenient tool for far-field calibration campaigns is a flying drone. Here we
make use of an octocopter to place a calibrated source at freely chosen
positions above the radio detector array. Special emphasis is put on the
reconstruction of the octocopter position and its accuracy during the flights.
The antenna response pattern of the radio detector stations was measured in a
recent calibration campaign. Results of these measurements are presented and
compared to simulations. It is found that measurements and simulations are in
good agreement.
