What is the effect of excessive microphone gain on SSB transmissions?

Microphone gain controls the amplification level of the audio signal entering the transmitter. If the gain is set too high on a Single Sideband (SSB) transmission, the audio amplifier gets overdriven, which clips the peaks of the voice waveform. This results in heavily distorted transmitted audio, making it difficult for the receiving station to understand you. Excessive gain can also cause 'splatter,' which creates interference on adjacent frequencies. However, it does not affect the actual operating frequency (frequency instability) or alter the antenna system's physical or electrical characteristics (increased SWR).