Question 6A368

Neutralization is the process of counteracting internal feedback, primarily due to inter-electrode capacitance within the active device (tube or transistor), which can cause an RF amplifier stage to become unstable and oscillate. When neutralizing an RF amplifier, especially one using a triode or certain transistor types, a common method involves removing the plate voltage (or output power supply) to prevent actual oscillation, then applying a small RF signal to the input. By varying the tuning of the plate tank circuit while observing a sensitive RF indicator (like an RF amp meter or voltmeter) at the output, one can detect residual RF feed-through from the input to the output. Adjusting the neutralizing capacitor or circuit to minimize this feed-through, such that the indicator shows no change as the plate tank is tuned through resonance, ensures the amplifier is neutralized. Thus, option A accurately describes this practical method. Option B is incorrect because an SWR meter measures standing waves on a transmission line and is used for matching the output to an antenna, not for internal amplifier neutralization. Option C describes design considerations (like increasing input impedance or adjusting inductance) that can contribute to stability, but it's not the *process* of neutralization itself, which often involves an adjustable component. Therefore, D is also incorrect.