8251 Series, RF Loads are portable, self-contained general purpose 50 ohm coaxial transmission line RF terminations requiring no outside power source or additional equipment. The loads are Oil-assisted convection cooling for safe, continuous operation up to 1000W full rated power. They provide accurate, dependable, and practically non-reflective termination for testing and adjusting transmitters under non-radiating conditions. The load consists essentially of a cylindrical film type resistor immersed in a dielectric coolant. The resistor, individually selected for its accuracy, is enclosed in a special tapered housing which provides a linear reduction in surge impedance directly proportional to the distance along the resistor.