Measurement:Conventional Practice

Conventional Practice

When calculating power level in dBm, we commonly make E2 = 0.775 V and R2 = 600 Ω. Note that E2 may be any voltage and R2 any resistance so long as together they represent

4. The term “gain” or “loss” always means the power gain or power loss at the system’s output due to the device under test.

Practical Variations of the dBm Equations

When the reference is the audio standard, that is, 0.77459 V and 600 Ω, then

For all of the values in Table 2.2 the only thing known is the voltage. The indication is not a level. The apparent level can only be true across the actual reference impedance. Finally, the presence or absence of an attenuator or other sensitivity control is not known. See Section 2.20 for an explanation of VU.