[Boatanchors] Tube Oscillator Circuit Question

[Jacques Fortin]

Hello Scott,

What you see is normal.
The BFO tube operates in class C, then it only draws current when the grid
voltage goes over a given value (it is self-biasing, anyways).
As you only have a resistive load on the plate, you see a sudden drop in the
plate voltage when the tube conducts to "push" the resonant circuit for
another turn again, then this voltage recovers more or less exponentially
due to the capacitive load on the plate.
The BFO in a National HRO behaves the same.

73, Jacques, VE2JFE