. The Bell System technical journal . char-acteristics falling within the following ranges. The numbers representthe range containing 90 per cent of the tubes tested. Accelerator Voltage for 40 ma 2,500-2,700 Helix Voltage for maximum low-level gain 2,350-2,450 Low-level gain 33-37 db Gain at 5 watts output 31-35 db Maximum power output J dbm \( watts) // 45 / y // ^ 1 ,70 MA 40 / ^ r^ ncx^6o >v K / ^ N k /) \^ f 7 ^ r^^^° \ \ 35 / / y^ / ^^s-l Nl \ /// Y // ^^^0 N \ k ^ 30 LU mu UJ a 25 z / V/i r^ // ^>^ i N L N \ lj[/ / // --^ k \ \ ^ M ^ / / ^ k \ 1 K \ \ z ^o 1 \ \ \
. The Bell System technical journal . char-acteristics falling within the following ranges. The numbers representthe range containing 90 per cent of the tubes tested. Accelerator Voltage for 40 ma 2,500-2,700 Helix Voltage for maximum low-level gain 2,350-2,450 Low-level gain 33-37 db Gain at 5 watts output 31-35 db Maximum power output J dbm \( watts) // 45 / y // ^ 1 ,70 MA 40 / ^ r^ ncx^6o >v K / ^ N k /) \^ f 7 ^ r^^^° \ \ 35 / / y^ / ^^s-l Nl \ /// Y // ^^^0 N \ k ^ 30 LU mu UJ a 25 z / V/i r^ // ^>^ i N L N \ lj[/ / // --^ k \ \ ^ M ^ / / ^ k \ 1 K \ \ z ^o 1 \ \ \ \ T m/ 1 1 1 L N i *^ y 5 juj/l A ^ \ \ \ 1 \ \ ^ / 1 N <5 MA N 1 \ \ \l 0 /f \ \ \ 2000 2100 2200 2300 2400 2500 2600 2700 HELIX VOLTAGE IN VOLTS 2800 2900 3000 Fig. 29 — Low-level gain as a function of helix voltage for various beam cur-rents. The dotted line represents the locus of the maxima of the curves. TRAVELING WAVE TUBE FOR O-OOO-MC RADIO RELAY 1325. FREQUENCY IN KILOM EGACYCLES PER SECOND Fig. 30 — Low-level gain and helix voltage for maximum gain as functions offrequenc} for several beam currents. The TWT was matched to the waveguide(with tuners where necessary outside of the 5,925 to 6,425-mc range) at each fre-(luency. The solid curves show the gain-frequency characteristic with the helixvoltage adjusted for maximum gain at 6,000 mc for each beam current and thenheld constant as frequency was changed. Experimental points correspond to thiscondition. The dotted curves show how the characteristics change when helixvoltage is optimized at each frequency. The optimum helix voltage increases byabout 100 volts in going from 6,000 down to 4,500 mc because of slight dispersion inthe phase velocity of the helix. Operation Over an Extended Range We now turn to a consideration of tj^pical Ml789 characteristics overan extended range of beam current, frequency, and magnetic field.* Weshall concentrate
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