What is the primary purpose of an RF amplifier in a receiver?

The overall noise figure of a receiver is largely determined by its very first amplification stage. By placing a low-noise RF amplifier right at the antenna input, the receiver can boost the signal-to-noise ratio before the signal hits the inherently noisy mixer stage. While the RF amplifier does provide some gain, the vast majority of a superheterodyne receiver's gain is actually developed later in the Intermediate Frequency (IF) stages. Thus, the primary focus of the RF amplifier is establishing a low noise figure, not providing bulk amplification.