Final answer:
The correct gain for the RF amplifier stage in a receiver is determined by the desired signal-to-noise ratio to ensure clear and audible output without excessive noise.
Step-by-step explanation:
The gain used in the RF amplifier stage of a receiver should be determined by the desired signal-to-noise ratio. The gain is crucial in ensuring that the receiver can amplify the signal sufficiently to produce a clear audio output without introducing too much noise. While other factors such as the quality of headphones and the length of the antenna might influence the overall user experience, they do not directly determine the appropriate gain. The frequency of the transmitted signal determines the resonant frequency at which the receiver should be tuned for optimal pickup of the signal and does not dictate the amplifier gain.