Ham Radio - RF Units Conversion

Decibel Conversions

dB = 10 log [P2/P1]

Decibels relative to Power

Decibel Conversions

dB = 20 log [V1/V2]

Decibels relative to Voltage across same resistance

Decibel Conversions

dB = 20 log [I1/I2]

Decibels relative to Current through same resistance

Decibel Conversions

dBmV = 20 log [Signal (mV)/1mV]

Decibels relative to one microvolt across same resistance

Decibel Conversions

dBm = 10 log [Signal (mW)/1mW]

Decibels relative to one milliwatt

Decibel Conversions

dBmA = 20 log [Signal (mA)/1mA]

Decibels relative to one microamp through same resistance

Power Conversions

dBm = dBw + 30

Conversion from dBw to dBm.

Voltage Conversions

dBuv = dBv + 120

Conversion from dBv to dBuv.

Voltage to Power

dBm = dBmV - 107

Where the constant 107 is as follows:
* RF systems are matched to 50^W
P = V² / R
10Log₁₀[P] = 20Log₁₀[V] - 10Log₁₀[50^W]
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.

Power Density

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[1000] = 30

Conversion Units
dB = decibels (Log10)
u = 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
dBuV = decibels relative to one microvolt
dBuA = decibels relative to one microamp
V = Volts
A = Amps
I = Current
R = Ohms (50)
W = Watts
P = Power
M = Meter