How much change in signal strength is typically represented by one S unit?

By convention among most amateur radio receiver manufacturers, one 'S unit' on a signal strength meter corresponds to a change of 6 decibels (dB). Because 6 dB represents a voltage ratio of 2:1 or a power ratio of 4:1, increasing a signal by one S unit requires quadrupling the transmitter power at the source. While some older or uncalibrated receivers may not track exactly to this standard in practice, 6 dB is the universally accepted standard for exam purposes and theoretical calculations.