The HP Agilent 5382A offers sensitivity of 25 mV rms (30Hz to 10MHz) and 50 mV rms (10Hz to 225MHz).
Input impedance is 1 Mohm, <40 pF
Input attenuation is selectable between x1, x10, and x100.
Resolution is direct count: 1Hz in 1 S and gate time is 0.1 S, 1 S and 10 S. 8-digit LED display provides good resolution and non significant zero blanking.