Abstract: Radar tubes are assessed based upon an observation that faulty radar pulses have a significantly increased content of undesired high frequency components in their cathode current sensed at the cathode lead of an operating radar transmitting tube. The invention exploits this observation in a simple, relatively low-cost device that can be built into a radar system to be put under test. The current at the transmitting tube's cathode is high-pass filtered to pass only those frequency components known to be indicative of faulty transmitting tubes. The filter output is converted into an analog output having an amplitude proportional to the amplitude of the high frequency voltage components passing through the filter. The high-pass output is smoothed and is fed to an analog-input, digital-output threshold amplifier. The threshold amplifier provides a TTL output that indicates whether its smoothed input amplitude represents a good radar pulse or a faulty pulse.