Abstract: Describes the design and experimental results for high gain and low-distortion UHF linear middle power transistors, used in UHF CATV main cable repeater. Based on researching the dependence on the distortion and gain on device paramaters, Optimum design for Low-distortion transistor is decribed. Transistor 3DA300 succeeds in achieving satisfac tory performances If IM3=-60dB, output power level P_out≥ 110dBμv.. Also insertion gain for|S_21e|²≐10dB at 500MHz is obtained.