The HP 8616A Signal Generators provide stable, accurate signals from 1800 to 4500 MHz. Both frequency and attenuation are set on direct-reading digital dials. Selectable functions include CW, leveled output, square-wave modulation, and external AM, FM and pulse modulation . Modulation can be accomplished simultaneously with or without leveling. Two RF power outputs are simultaneously available from separate front-panel connectors. One provides at least 10 mW (2 mW above 3000 MHz) or a leveled output from 0 to -127 dBm. The other is at least 0.5 mW across the band. The signal can be used for phase-locking the signal generators for extreme stability, or it can be monitored with a frequency resolution without adversely affecting the primary output. A unique PIN diode modulator permits amplitude modulation from dc to 1 MHz or RF pulses with a 2 microns rise time. This broad modulation bandwidth permits remote control of output level or precise leveling is also obtained by using a PIN modulator. The 8616A can also be used with companion modulators, HP 8403A modulators and HP 8730-series PIN modulators to provide 80 dB pulse on/off ratio. In addition, TWT amplifiers can be used with these generators to provide high power levels.