Squegging is an unstable operating mode in an oscillator circuit where the main high-frequency oscillation is modulated or interrupted by a lower-frequency on-off cycle. It typically happens when the circuit builds up too much bias voltage across a coupling capacitor, cutting off the active device until the charge bleeds away. Designers usually fix it by adjusting the RC time constant in the biasing network.
The RF stage is squegging again, so try dropping the grid leak resistor value to bleed off that charge faster.
If your oscillator sounds like a motorboat on an audio monitor, it is almost certainly squegging.
Related terms
Armstrong oscillator
A classic LC oscillator circuit that uses a tickler coil to provide positive feedback.
VCO
A voltage-controlled oscillator is a circuit that changes its output frequency based on a DC input voltage.
Parasitic
An unintended electrical property like capacitance or inductance that exists physically in a circuit.