. The Bell System technical journal . 70 2 A Fig. 2—The 702A and 709A vacuum tubes achieve either greater antenna directivity or smaller size. Since satisfactoryvacuum tube converters were not available for these frequencies, the siliconrectifier had to be used. Unfortunately the silicon rectifier, as then avail-able, was subject to permanent damage if subjected to but very smallamounts of power as compared with the magnetron power levels. An active program of work was initiated at the Bell Telephone Labora-tories to obtain designs of TR boxes offering adequate protection for contactrectifiers
. The Bell System technical journal . 70 2 A Fig. 2—The 702A and 709A vacuum tubes achieve either greater antenna directivity or smaller size. Since satisfactoryvacuum tube converters were not available for these frequencies, the siliconrectifier had to be used. Unfortunately the silicon rectifier, as then avail-able, was subject to permanent damage if subjected to but very smallamounts of power as compared with the magnetron power levels. An active program of work was initiated at the Bell Telephone Labora-tories to obtain designs of TR boxes offering adequate protection for contactrectifiers at any power levels then available or contemplated. Three tubeswere developed, the 721A, 724B and 1B23 vacuum tubes shown in These tubes are used at frequencies in the vicinity of 3000 megacycles,10,000 megacycles, and 1000 megacycles respectively. They arc all of the 52 BELL SYSTEM TECHNICAL JOURNAL.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
