. The Bell System technical journal . oltage and theback piston of the coupling of Fig. 101 to the values which gave maximum power. Theseconditions were then held fixed for the remainder of the chart. excursion which will be produced when a VSWR of 3 db is presented to thetransmitter and the phase is varied over 180°. Fig. 107 gives the pullingfigure as a function of frequency for the 2K54 and 2K55. The requirementson the pulling figure for the 2K54 and 2K55 were not severe, since in theAN/TRC-6 system the tube is coupled to the antenna by a very short waveguide run and, furthermore, the anten
. The Bell System technical journal . oltage and theback piston of the coupling of Fig. 101 to the values which gave maximum power. Theseconditions were then held fixed for the remainder of the chart. excursion which will be produced when a VSWR of 3 db is presented to thetransmitter and the phase is varied over 180°. Fig. 107 gives the pullingfigure as a function of frequency for the 2K54 and 2K55. The requirementson the pulling figure for the 2K54 and 2K55 were not severe, since in theAN/TRC-6 system the tube is coupled to the antenna by a very short waveguide run and, furthermore, the antennas are fixed. REFLEX OSCILLATORS 615 Investigation of the pulling figure of early models of the 2K55 led, how-ever, to the disclosure of one unforeseen pitfall arising from the existence ofelectronic hysteresis. It had at first been considered that electronic hystere-sis would not be of importance in the transmitter tube, where the feature ofelectronic tuning was of no importance. This might be true in a CW oscilla- FREQUENCY POWER. Fig. 104.—Rieke diagram for the 2K54 oscillator at a nominal frequency of 4350megacycles. The unity iswr point was obtained as described in Fig. 103. tor, but in a pulsed oscillator the existence of hysteresis resulted in an un-foreseen reduction of the sink margin. Since the oscillator is being pulsed,for each pulse the oscillating conditions are being re-established. Althoughthe cathode-repeller voltage need not vary during the pulsing, the fact thatthe cathode-resonator voltage is being changed means that for each pulsethe drift angle in the repeller space varies on the rise and fall of the effect during the rise of the pulse is the same as though the repeller 616 BELL SYSTEM TECHNICAL JOIRNAL voltage were made less negative. In other words, on the rise of each pulsethe situation is equivalent to that in a ClT oscillator when, for a fixedresonator voltage, one starts with a repeller voltage too negative to permitoscillation and then
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