Conversion factors – ETS-Lindgren 3147 Log Periodic Dipole Array Antenna User Manual
Page 32
If a long coaxial cable is used between the antenna and the receiving device, or
the frequency of the observation is more than several tens of MHz, the losses in
the coaxial cable, Ae, must be included in the computation. In this case the
computation is:
RF Voltage, dB(µV) + Cable Loss, dB + Antenna Factor, dB (m
-1
) =
Field Strength dB (µV/m)
Ea = Va + AF + Ae
Conversion Factors
Following are some useful conversion formulas.
dBm = dB(µV) – 107
dB(mW/m
2
) = dB(µV/m) – 115.8
dB(µV/m) = dB(µV) + AF
V/m = 10
dB(µV/m) – 120
20
dB(µA/m) = dB(µV/m) – 51.5
A/m = 10
dB(µA/m) – 120
20
dB(W/m
2
) = 10 log(V/m A/m)
dB(mW/m
2
) = dB(W/m
2
) + 30
dB(pT) = dB(µA/m) + 2.0
The constants that appear in the above equations are obtained as follows:
In the first equation, the power is related to the voltage via the system impedance
as:
P =
V
2
R
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Radiated Emissions Measurement