Photovoltaic (PV) systems have caused residential and commercial building fires when an electrical arc fault initiates in the conduction path. Article 690.11 in the United States 2011 National Electrical Code requires new photovoltaic systems on or penetrating a building to include a listed arc fault protection device to prevent additional fires. In response, manufacturers are creating arc fault circuit interrupters (AFCIs) using electrical frequencies for detection, but their operation is not fully characterized. Sandia National Labs has undergone a major effort to identify detection difficulties and establish tests for PV AFCI manufacturers to ensure their product can robustly detect arcing conditions while avoiding false trips from noise sources. In previous studies, arc fault signatures have been compared to string noise and frequency-dependant attenuation through PV modules has been quantified. In this paper, a frequency response analyzer was used to measure radio frequency (RF) propagation through arrays of varying irradiance and size. Irradiance did not affect module frequency response, but the length of unshielded wiring significantly affected the frequency response of the system above 100 kHz due to RF effects. Based on the RF affects in PV systems, it is recommended that arc fault circuit interrupter manufacturers select detection frequencies below 100 kHz.