In a circuit diagram, what is the effect of installing a small variable capacitor instead of the dashed line?

Installing a small variable capacitor instead of the dashed line in a circuit diagram typically serves to modify the capacitance in the circuit, which ultimately influences the oscillation conditions. A variable capacitor allows for fine-tuning of capacitance, making it possible to stabilize the circuit against unwanted frequency oscillations, often referred to as parasitic oscillations.

By carefully adjusting the capacitance through the variable capacitor, the circuit can achieve a better balance, which reduces the likelihood of generating parasitic oscillations that can occur due to components' inherent characteristics. Therefore, its incorporation can lead to decreased parasitic oscillations in the circuit, thereby improving the overall performance and stability of the oscillating system.

In this context, a change to a variable capacitor doesn't eliminate oscillations entirely, but it allows for control over capacitance, ultimately working toward reducing the unwanted oscillatory behavior induced by other circuit elements.