The 451 Microwave Pulse Counter automatically and directly measures the frequency of pulse modulated microwave signals between 300MHz and 18GHz and pulse widths of 100 ns, with no minimum or maximum pulse repetition frequency limits. Capable of measuring the frequency of CW signals, and carrier signals with FM modulation up to 40MHz peak-peak deviation at 10MHz modulation rates. Sensitivity is -10 dBm to 10GHz; -5 dBm to 18GHz. Input impedance is 50 ohms. Overload protection provided up to 1 W peak from 925MHz to 18GHz. Direct reading display with 10kHz resolution over entire operating range. Gate times are 100 µs and 1 ms. Timebase is 10MHz stability of <3x10E-07/month. Display is 7-digit LED with fixed decimal point, leading zero suppression (except during no input signal).