Push-Pull Piezo-Electric Oscillator Circuits

Comparative tests have been made of five different push-pull piezo-electric oscillator circuits. Two of these circuits use three-element tubes: (1) crystal in four-electrode mounting connected to the grids and anodes, (2) crystal in two-electrode mounting connected to the grids. The other circuits use four-element tubes, (3) screen-grid tubes with the crystal in a four-electrode mounting connected to the control grids and anodes, (4) space-charge-grid tubes, quartz crystal in four-electrode mounting connected to the control grids and anodes, (5) space-charge-grid tubes, crystal in two-electrode mounting connected to the control grids. These circuits have been tested at 90 kc for relative power output and variation of frequency with circuit constants. The type UX-210 tube was used with the circuits (1) and (2) and type UX-865 screen-grid tube with the circuits (3), (4), and (5). The ratios of the power outputs at 90 kc of the circuits (1), (2), (3), (4), and (5) are 10.7, 9.6, 12.9, 1.68 and 1.0, respectively. The power output of circuit (3) at 315 volts with the grid bias through 2-megohm resistors was 0.50 watt at 90 kc. Using the same circuit with 450 volts on the anodes and the grid bias through chokes the power output was 5.20 watts. Considering the low frequency these are reasonable values. The power output of the circuits (4) and (5) is abnormally small, but this may be due to the fact that the UX-865 is not particularly well adapted for use in this type of circuit.