3B/850A . (4242) Triode 4242A CATHODE. Thoriated tungsten filament. Voltage 10 Vv Nominal current 3.25 A Peak emission 2 A RATING. Amplification factor \ Measured at Va 12.0 Impedance IkV, Vg,-55 V 3,000 ohms DIRECT INTER-ELECTRODE CAPACITIES. Grid to anode 13 pF Grid to filament 6.5 pF Anode to filament 4 pF DIMENSIONS. Overall length 204 mm, Maximum diameter 59 mm. Base Large 4-pin bayonet Net weight 160 g. MAXIMUM RATINGS. Maximum direct anode voltage 1,250 Vv Maximum direct anode current 150 mA Maximum anode dissipation 85 Ww Maximum direct grid current 50 mA Maximum frequency for above rating 6 Mc/s Maximum anode voltage for frequency of 30 Mc/s 600 Vv NOTE.This valve should be mounted so that the plane of the filament is vertical. August 1945 3B/850AI 3B/850A (242A) Triode 4242A TYPICAL OPERATING CONDITIONS. AUDIO FREQUENCY. Class B. Amplifier or Modulator. For balanced 2-valve circuits. Direct anode voltage 1,250 1,000 V Anode current per valve zero signal 25 25 mA Anode current per valve maximum signal 150 150 mA Grid bias 95 I5 V Anode dissipation 64 56 W Load resistance 9,600 8,000 ohms Peak signal grid to grid 165 140 V *Approximate grid driving power 4 2W Maximum output 2 valves 245 185 W RADIO FREQUENCY. Class B. Telephony. Modulated Carrier applied to Grid. (Carrier conditions per valve for use with 100% modulation). Vv Direct anode voltage 1,250 1,000 Grid bias 100 80 V Direct anode current 100 125 mA *Direct grid current 2 1.5 mA approx. Peak R.F. grid voltage 12 105 V Power output 4l 40W Class C. Amplifier. Anode subjected to modulation. (Carrier conditions per valve for use with 100% modulation.} Direct anode voltage 1,000 V max. 750 V Grid bias 195 --180 V Direct anode current 150 150 mA Peak R.F. grid voltage 295 285 V *Direct grid current \7 17 mA approx. Power output 110 80 W Class C. Amplifier or Oscillator, Unmodulated. Direct anode voltage 1,250 1,000 V Grid bias 153 133 V Direct anode current 150 150 mA Peak R.F. grid voltage 243 223 V *D.C. grid current 1.5 10 mA approx. Power output 140 108 W * Subject to wide variation dependent upon the impedance of the load circuit. August 1945 3B/850A2 3B/850A 4242A Triode (202A) NRA GRID CURRENT (m | 1000 ANODE VOLTS + ANODE CURRENT (mA) 9 500 1000 ANODE VOLTAGE (V) August 1945 3B/850A3 3B/850A (4242A) Triode Co 4242A ~~ 59mm MAX] 204 mnMAX PLANE OF PY FILAMENT. August 1945 3B /850A4