Sensitive S band travelling-wave phototube

A description is given of a travelling-wave phototube (t.w.p.) having an S 20 photocathode with a nominal frequency range 2¿4 Gc/s. The power output and noise equivalent power of this tube are compared with other light detectors operating in a similar frequency range. A description is given of a light-communication link which has been set up employing the t.w.p. as detector.