S-Units at-a-glance

• An S-METER is calibrated by connecting a signal generator to the 50 ohm antenna terminal and setting the output power to 50uV, or -73dBm, and adjusting the S-meter calibration pot for a reading of S-9. 
• Many commercial receivers indicate non-standard readings. The calibration point may be correct, but the power level change between s-units are not in 6 dB steps.
• Notice that as the power level increases by 6dB, the voltage level doubles for each S-Unit from S1 through S9+6dB. 
• One S-unit corresponds to a difference of 6 decibels (dB), equivalent to a voltage ratio of two, or power ratio of four