When mounting an antenna on a craft a prize always has to be paid in the form of an increase in signature i.e. one is easier to detect on radar. In this report a measurement of the radar cross section (RCS) on a conformal array antenna mounted on a metallic half sphere is described. The metallic half sphere is to be thought of as the nose of a small flying craft for example an UAV (Unmanned Airborne Vehicle). The array consists of patches placed in a grid that follows the structure i.e. it is conformal. The measurement setup is a wooden arc (a so-called NRL arc) with antennas mounted for measurements. The antennas are two ridge waveguide horns, one transmitter and one receiver and they are used to measure the reflection, S12 , from the object of interest (the patch antenna). The signal is registered by a network analyzer "Wiltron 37269B". The frequency is scanned from 2 to 20 GHz. A reference measurement is made on the half sphere where and where possible interfering signals are excluded from the background. Comparing metallic half sphere only with metallic half sphere plus antenna a significant signature from the antenna can be noticed in the frequency span from 16 to 18 GHz.