They can be used as two-quadrant, single-balanced mixers or (de)modulators with very linear qualities. Their mode of operation is similar to one-half of a Gilbert cell by applying an unbalanced signal f1 to the control grid and a 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 can be made into an oscillator. Two beam deflection tubes can be combined to form a double-balanced mixer.
More elaborate applications of the principle include:
2H21 and 5593 - Magnetically controlled "Phasitron" phase modulator tubes[3] used in early FM broadcast transmitters.[4][5]
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[6]
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[7]
6462Magnetic pickup tube, a 1-axis magnetometer with approx. 1 G (100 μT) resolution; the electron beam is electrostatically centered between two anodes while no magnetic field is present; the magnetic field to be detected will then deflect the beam more towards one of the anodes, resulting in an imbalance between the two anode currents
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.[8]
Parallel-outputPCM tube, an analog-to-digital converter with per-bit, vertical anode bars with perforations encoding the Gray code.[9] A flat, horizontal sheet beam was then vertically deflected by the input analog signal across the perforated anode array, causing the digital representation of the analog signal to appear on the anodes.
With two-axis deflection:
Serial-output PCM tube, an analog-to-digital converter with one anode having binary-encoding perforations.[10][11] As in an oscilloscope, the beam was swept horizontally by a sawtooth wave at the sample rate while the vertical deflection was controlled by the input analog signal, causing the beam to pass through higher or lower portions of the perforated anode. The anode collected or passed the beam, producing current variations in binary code, one bit at a time.
7828Scan conversion tube, an analog video standards transcoder consisting of a CRT/camera tube combination. The CRT part does not write onto a phosphor, but onto a thin, dielectric target; the camera part reads the deposited charge pattern at a different scan rate from the back side of this target.[14] The setup could also be used as a genlock.
