Your receiver's S-meter is calibrated to a standard of 6 dB per S-unit per a recommendation by the International Amateur Radio Union (IARU). The S-meter shows S9 when receiving a station transmitting with 100 watts. Neglecting propagation changes, what transmitter power would cause your receiver's S-meter to read S8?

The standard calibration for an amateur radio S-meter is 6 decibels (dB) per S-unit. Therefore, dropping from S9 down to S8 represents a signal strength reduction of exactly 6 dB. In radio electronics, every 3 dB decrease corresponds to cutting the transmitter power in half. A 6 dB decrease requires cutting the power in half twice. Starting at a transmitter power of 100 watts, the first 3 dB drop reduces the power to 50 watts. The second 3 dB drop (completing the 6 dB total) halves the power again, bringing it down to 25 watts.