Beam deflection tube

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Basic self-oscillating circuit

Beam deflection tubes, were cathode ray tubes with an electron gun, a beam intensity control grid, a screen grid, sometimes a suppressor grid, and two electrostatic deflection electrodes on opposite sides of the electron beam, that could direct the rectangular beam to either of two anodes in the same plane. They were used as two-quadrant, single-balanced mixers or (de-)modulators with very linear qualities, their mode of operation similar to one-half of a Gilbert Cell, by applying one, unbalanced, signal f1 to the control grid, and the other, balanced, signal f2 to the deflection electrodes, then extracting the balanced mixing products f1-f2 and f1+f2 from the two anodes.[1][2] Similar to a pentagrid converter, the cathode and the first two grids could be made into an oscillator. Two beam deflection tubes could be combined to form a double-balanced mixer.

They needed extensive shielding against external magnetic fields. The ballistic transistors currently under development employ a similar principle.

Examples[edit]

  • 6218/E80T - Modulated beam deflection tube, for pulse generation up to 375 MHz; single-anode version, shock-proof up to 500 g
  • 7360 - Balanced modulator or product detector up to 100 MHz
  • 6AR8, 6JH8, 6ME8 - Analog television chroma signal demodulators used in color TV receivers

More elaborate applications of the principle include:

  • 6090 - 18-channel analog demultiplexer for telecomms receiving channel banks, an electrostatic deflection field determines which one out of 18 anodes receives the electron beam controlled by a common grid[3]
  • 6170 and 6324 - 25-channel analog multiplexer for telecomms transmitting channel banks, a rotating magnetic deflection field determines through which one out of 25 grids the electron beam passes to the common anode[4]
  • E1T - Trochotron with a fluorescent-screen readout
  • QK329 - Square-law tube for use as a function generator in analog computers. A flat sheet beam is deflected across the anode which is partially covered by a parabolically stenciled screen "grid" that acts as the tube's output.[5]

References[edit]

  1. ^ M. B. Knight (1960). "A new miniature beam deflection tube". RCA Electron Tube Division. Retrieved May 30, 2013. 
  2. ^ H. C. Vance K2FF (1960). "SSB Exciter Circuits Using a New Beam-Deflection Tube". QST. Retrieved May 30, 2013. 
  3. ^ "6090 18 channel radial beam tube - multiple anode type data sheet" (PDF). National Union Electric Corporation. January 1956. Retrieved 15 June 2013. 
  4. ^ "6170 & 6324 25 channel radial beam tube - multiple grid type data sheet" (PDF). National Union Electric Corporation. December 1955. Retrieved 15 June 2013. 
  5. ^ Miller, Joseph A., Soltes, Aaron S., Scott, Ronald E. (February 1955). "Wide-band Analog Function Multiplier" (PDF). Electronics. Retrieved 15 June 2013.