What does an audio amplifier do in a transmitter?

Question

In transmitter schematics, usually there is an audio amplifier. I would like to know its purpose. Does simply amplifying the audio input create a stronger signal for transmission? So, basically, does increased audio power equate to increased range for the transmitter?

Answer 1

With reference to AF amplifiers in transmitters, it simply adjusts the level of the audio to  arrive at a desired level of modulation in the transmitter. The most desired level of course is 100%. For the range of the transmitter, it is the level of the RF carrier that counts and not the intelligence audio. You will only overmodulate the carrier and cause an unintelligible signal at the receiver.

Answer 2

Audio amplifiers do amplify audio signals since a microphone signal level can be to low to be of any use for the signal transmission. From there, the question is, what kind, or class of transmitter are you talking about, AM, or FM? In AM the audio is mixed with a low level carrier signal, and then amplified to the full power rating the station is going to transmit at. In FM, the amplified audio is used to frequency modulate, that is, cause the frequency to change at the same rate as the audio signal. The benefit of FM is that much more efficient transmitters can be used, such as class 'C' transmitters since the audio is not affected by that class of amplifier. The audio level has little to do with transmitter output power. It does, however, have a lot to do with the space in the spectrum that the radiated signal will occupy.