What is an "RF choke" used for in a transmitter?

An RF choke is specifically designed to block radio frequency (RF) signals while allowing direct current (DC) or low-frequency signals to pass through. This characteristic is crucial in the operation of transmitters, as it helps to isolate different components within the system, ensuring that high-frequency signals do not interfere with the stable operation of low-frequency circuits or power supplies.

In the context of a transmitter, the RF choke prevents RF energy from leaking back into the power supply or other components, which could cause unwanted oscillations or distortions in the output signal. By effectively filtering out RF interference, the choke contributes to maintaining the integrity of the signal being transmitted.

The other options do not accurately describe the function of an RF choke. Enhancing the power output or improving harmonics involves different mechanisms that do not relate to filtering out RF while allowing lower frequencies to pass. Mitigating interference from external noise sources may involve other types of devices or techniques, but the primary role of an RF choke is its selective filtering capability.