Measurements of High Frequency Amplification with Shielded-Grid Pliotrons

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Abstract
Tests of cascade high frequency amplification are described, using specially constructed tubes in which the control grid is electrostatically shielded from the plate. These tubes are free from internal feed-back, so that any number may be operated in series. The voltage amplification per stage depends only on the circuit impedance, and was found to be 200 at 50 kilocycles, 40 at 1000 k.c., and 7 at 10,000 k.c. Total amplifications as high as 2,000,000 in voltage were obtained and measured at 1000 k.c. It is shown that this is the largest amplification that can be usefully employed at any frequency. At 10,000 k.c. a total amplification of 10,000 was obtained. Examples are given of other applications, such as the amplification of small photo-electric currents, where shielding is advantageous.