There are various dBx measures of real signal characteristics. The most
common ones that I know of are dBm (dB over 1mW), dBV (dB over 1V,
presumably ignoring impedance and therefore really just a fancy-pants
amplitude measure) and dBc (dB under carrier, very important stuff to
measure phase noise in an oscillator or transmitter).
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RF power limitations (power into antenna) for the UK amateur radio
licences are expressed in dBW 26 dBW equals 400 Watts
15 dBW equals 32 Watts etc .

Frank GM0CSZ / KN6WH