An Investigation of Various Electrode Structures of Cathode Ray Tubes Suitable for Television Reception

The use of cathode ray tubes for television reception involves problems not encountered when the tubes are used for oscillograph work. This paper takes up various constructions which were tried showing the characteristic curve of each as well as the behavior of the spot under various conditions. It was found that it was possible to design a tube which would operate with a negative bias on the focusing (or modulating) electrode, and which required only a small input signal to modulate fully the intensity of the beam. Furthermore, it was found possible to keep the size of the spot constant while being modulated. By properly designing the elements, a variable control constant caused the curve of focusing electrode volts vs. accelerating electrode current to become steeper as the bias approached zero. This is desirable, as for higher light intensities a larger change in light is necessary to cause the corresponding reaction on the eye. Tubes made up with dual accelerating electrodes enabled higher intensities to be obtained and also permitted a separate adjustment of the size of the spot.