. The Bell System technical journal . ficient of expansion and, as they arefastened to the channel at its ends, they remain cool and do not expandappreciably as the channel is heated. The purpose of the multi-leaf con- REFLEX OSCILLATORS 579 struction of the bow is to reduce the internal stresses produced by bendingduring the tuning action. A cathode, control grid and a pair of focussing wires are supported bymicas in a position facing the open side of the U channel. The channelserves as an anode for the cathode current, which is controlled by the focussing wires beam the cathode curr
. The Bell System technical journal . ficient of expansion and, as they arefastened to the channel at its ends, they remain cool and do not expandappreciably as the channel is heated. The purpose of the multi-leaf con- REFLEX OSCILLATORS 579 struction of the bow is to reduce the internal stresses produced by bendingduring the tuning action. A cathode, control grid and a pair of focussing wires are supported bymicas in a position facing the open side of the U channel. The channelserves as an anode for the cathode current, which is controlled by the focussing wires beam the cathode current into the anode. The grid isproportioned so that under all operating conditions it remains negative,and the control system need supply no power to it. The heating of the channel by the electron bombardment causes it toexpand with a large differential with respect to the bow. As a result thebow flattens out and its center moves toward the channel. The purposeof this construction is to provide a magnification of the expansion of the. Fig. 75.—An external view of the 2K45—an early thermally tuned reflex oscillatordesigned by the Bell Telephone Laboratories. channel which by itself would provide insufficient motion. The crossmember welded to the center of the bow and the vertical struts transmit themotion of the bow to the diaphragm which supports one of the cavity action is illustrated in Fig. 78 which shows a series of X-ray views of anoperating tube. Thus, the first view shows the conditions for no powerapplied to the tube, the second, for the tube operating but with the tunergrid biased to cut-ofT. The following views show the behavior with progres-sive increases in the power into the tuner channel. The ramifications in the design of a thermal tuner are many and the possi-ble configurations of the mechanism will depend greatly on the individualrequirements of the application. It is possible, however, to lay down somebasic principles. These are concerned wi
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