What must be added to the dBm reading when measuring receiver sensitivity?

When measuring receiver sensitivity, it is essential to consider all losses that might affect the signal before it reaches the receiver. This includes the attenuations of the directional coupler and any connecting cables.

The dBm reading provides the power level of the signal that the receiver is receiving, but it does not account for any losses that occur due to the coupling or transmission of the signal. The directional coupler introduces some level of attenuation, as does the connecting cable, which can significantly affect the actual signal strength reaching the receiver.

By adding the attenuations of the directional coupler and connecting cable to the dBm reading, you can obtain a more accurate measure of the receiver's sensitivity. This adjustment ensures that the measurements reflect the actual conditions under which the receiver operates, allowing for more precise evaluations of its performance.