Calibration of the logarithmic-periodic dipole antenna (LPDA) radio stations at the Pierre Auger Observatory using an octocopter

An in-situ calibration of a logarithmic periodic dipole antenna with a frequency coverage of 30 MHz to 80 MHz is performed.Such antennas are part of a radio station system used for detection of cosmic ray induced air showers at the Engineering Radio Array of the Pierre Auger Observatory, the so-called Auger Engineering Radio Array (AERA).The directional and frequency characteristics of the broadband antenna are investigated using a remotely piloted aircraft carrying a small transmitting antenna.The antenna sensitivity is described by the vector effective length relating the measured voltage with the electric-field components perpendicular to the incoming signal direction.The horizontal and meridional components are determined with an overall uncertainty of 7.4 +0.9-0.3 % and 10.3 +2.8 -1.7 % respectively.The measurement is used to correct a simulated response of the frequency and directional response of the antenna.In addition, the influence of the ground conductivity and permittivity on the antenna response is simulated.Both have a negligible influence given the ground conditions measured at the detector site.The overall uncertainties of the vector effective length components result in an uncertainty of 8.8 +2.1 -1.3 % in the square root of the energy fluence for incoming signal directions with zenith angles smaller than 60 • .