Since the levels in antenna technology, in community antenna systems and EMC measurement technology are very low, one uses the dB µV, decibel microvolt as reference level. The reference value for 0 dBµV is 1 µV. 60 dBµV corresponds to 0 decibel millivolts( dBmV).
A direct relationship can be established between dBm and dBµV via the power and the input resistance. According to this, the interference voltage of 1 mW at 50 ohms is 223.6 mV. From this relation one can calculate the relations between dBµV and dBm. 0 dBµV are -107 dBm, 20 dBµV -87 dBm, 40 dBµV -67 dBm and so on.