The 491C TWT Amplifier covers the 2 to 4GHz frequency range with 1 W output and 30 dB gain. Input/output impedance is 50-ohms, type N female connectors. Sensitivity: modulation input of >-20 V peak reduces RF output by >/=20 dB from DC to 50 kHz. Frequency response is DC to 500kHz (3 dB), pulse response is <1 µs rise and fall times. Features include front-panel gain adjust, cathode current meter, and modulation input.