Unmanned aerial vehicles (UAVs) are increasingly used to accelerate radio frequency electromagnetic field (RF-EMF) studies and performance assessments of mobile networks, particularly in locations that are difficult or hazardous to access. However, a conductive carbon-fiber airframe located in the reactive near-field of a receive antenna may detune the antenna and distort local field conditions, potentially compromising far-field assumptions. This study quantitatively investigates UAV-induced measurement errors in cellular frequency bands and their dependence on antenna-frame separation. A controlled laboratory procedure compares reference measurements with UAV-mounted configurations while varying the receive antenna distance from the airframe over the 700-3500 MHz range. Results indicate that, for the examined UAV platform and antenna placements, the measured differences relative to the reference are mostly below 3 dB across the investigated frequency range. Increasing the antenna-frame separation reduces these differences by approximately 1-1.5 dB for positions beyond 4 dot left parenthesis lamda slash 8 right parenthesis 4·(λ/8) compared with closer positions. These findings suggest that, under controlled conditions, UAV-mounted configurations can provide sufficiently accurate results for RF-EMF and performance assessment applications. However, the results are specific to the investigated UAV platform, antenna configuration, and laboratory conditions, and cannot be directly generalized without further validation.