Nick,
Thank you for your inquiry. The RDP118 was the 10"CRT type display used with the original 1832/1932/1942 series of radar's (no longer available). The display was versatile in that the same display unit could function with any of the three different antenna arrays. As such, however, proper installation required that the installer designate / identify which of the three possible antenna configurations the display would be operating with. While pressing and holding down the GAIN button (HM-OFF), press the MENU key five times o display the factory menu. Item number three (3) of the Factory Menu is Model; select either "M-1832" (for the dome antenna) or select "Others" (for either of the open array versions of the antenna). Press MENU to close this menu and return to normal operation.