Final answer:
The primary purpose of an RF amplifier in a receiver is to increase the strength of the weak radio frequency signals received, enabling them to be processed into audio or video.
Step-by-step explanation:
The primary purpose of an RF amplifier in a receiver is to increase the strength of the received signal. This process involves amplifying the very weak radio frequency (RF) signals that are picked up by the receiver's antenna so that they can be processed and converted into a usable audio or video format. An RF amplifier is essential in a radio receiver to ensure that the resonant frequency of the carrier wave is sufficiently strong to be further processed, allowing for the original audio signal to be replicated accurately and with enough power to drive a speaker or to be recorded.
The RF amplifier does not provide image rejection, amplify audio frequencies, or control the local oscillator; rather, its sole function is to boost the signal's strength at the radio frequency level before any other processing takes place within the receiver.