The 8591A offers frequency accuracy and a wide range of options for applications that demand higher performance. The HP 8591A has a frequency range of 9kHz to 1.8 GHz and amplitude range of -115 to +30 dBm. It has a standard 7.5 ppm frequency accuracy that can be improved with an optional precision frequency reference to marker count accuracy of 230 Hz at 1 GHz or 2.3 kHz at 18 GHz.