Commercial availability of small UAV's and their capabilities raises the question of the ability to defend against these assets, which could be used, or misused, as the air threat. This paper brings results of the series of experiments with the commercial quadcopter DJI Phantom 2 Vision that were performed by Department of Air Defense Systems/University of Defense Brno members in laboratory (anechoic chamber) and in the exterior as well. Terrain tests were done using military Doppler radar, with respect to the laboratory-measured radar cross section. Besides this, the visibility, audibility and other aspects of possible misuse of the drone were determined and analyzed for to find possible and identify optimal means for their detection.