Ham Radio - RF Units Conversion Decibel Conversion: Power dB = 10 log [P2/P1] Decibels relative to Power Decibel Conversion: Voltage dB = 20 log [V1/V2] Decibels relative to Voltage across same resistance Decibel Conversion: Current dB = 20 log [I1/I2] Decibels relative to Current through same resistance Decibel Conversion: Milliwatts dBm = 10 log [Signal (mW)/1mW] Decibels relative to one milliwatt Decibel Conversion: Microvolts dBmV = 20 log [Signal (mV)/1mV] Decibels relative to one microvolt across same resistance Decibel Conversion: Microamps dBmA = 20 log [Signal (mA)/1mA] Decibels relative to one microamp through same resistance Power Conversion: dBw to dBm dBm = dBw + 30 Conversion from dBw to dBm. Voltage Conversion: dBv to dBmv dBmv = dBv + 120 Conversion from dBv to dBuv. Voltage to Power Conversion: dBmv to dBm dBm = dBmV - 107 Where the constant 107 is as follows:* RF systems are matched to 50W P = V2 / R 10Log10[P] = 20Log10[V] - 10Log10[50W] V = (PR)0.5 = 0.223 V = 223000 mV For a resistance of 50W and a power of 1 mW: 20Log10[223000mV] = 107 dB Power Density dBw/M2 = 10Log10[V/M - A/M] Decibel-Watts per square meter. dBm/M2 = dBw/M2 + 30 Where the constant 30 is the decibel equivalent of the factor 1000 used to convert between W and mW: 10Log10 = 30 Electric Field Voltage V/M = 10{[(dBmV/M) -120]/20} Electric Field Voltage in volts per meter Electric Field Current dBmA/M = dBmv/M - 51.5 Where the constant 51.5 is a conversion of the characteristic impedance of free space (120p) into decibels: 20Log10[120p] = 51.5 A/M = 10{[(dBmA/M) -120]/20} Electric Field Current in amps per meter Conversion Units dB = decibels (Log10) m = micro = 10E-6 m = milli = 10E-3 dBw = decibels relative to one watt dBm = decibels relative to one milliwatt dBV = decibels relative to one volt dBmV = decibels relative to one microvolt dBmA = decibels relative to one microamp V = Volts A = Amps I = Current R = Ohms (50) W = Watts P = Power M = Meter