How can a single-sideband phone signal be produced?

To generate a Single-Sideband (SSB) signal, a two-step process known as the 'filter method' is most commonly used. First, the audio signal and the radio-frequency (RF) carrier are fed into a balanced modulator. This stage suppresses the carrier, leaving only the upper and lower sidebands, which creates a Double-Sideband Suppressed-Carrier (DSB-SC) signal. Following the balanced modulator, a highly selective bandpass filter (such as a crystal or mechanical filter) is used. This filter is carefully tuned to pass only the desired sideband—either upper or lower—while steep attenuation rejects the other sideband. The resulting output is a true Single-Sideband signal.