M.E.C.’s 390-SG Series standard gain horn antennas are built to the sizes established in NRL Report No. 4433.1  These units are typically used to calibrate other antennas, as receiving or transmitting antennas, and as pick-up horns for field sampling.  A calibration curve is provided with each unit, calculated per the theory established and used by NRL.2  Material is aluminum with chromate conversion finish per MIL-C-5541, Class 3, and gray epoxy enamel.