An apparatus and method is disclosed to calculate the actual received desired channel power from the downstream transmit power of a Cable Modem Termination System (CMTS) when operating at the nominal line voltage and/or at the normal room temperature as per the DOCSIS specification. A Set-top Device produces a Downstream Power Management (DPM) gain measurement signal having a known power level. The Set-top Device embeds the DPM gain measurement signal onto a received downstream multi-channel communication signal. After embedding the DPM gain measurement signal onto the downstream multi-channel communication signal, the Set-top Device downconverts the combined DPM gain measurement signal and downstream multi-channel communication signal to recover one or more communication channels containing information of a broadcast. The Set-top Device measures a power level of a representation of the DPM gain measurement signal embedded within the one or more communication channels containing the information of the broadcast to determine a Set-top Device gain. The Set-top Device measures a power level of the one or more communication channels containing the information of the broadcast. The Set-top Device calculates the actual received desired channel power from the downstream transmit power of the CMTS based on the Set-top Device gain and the power level of the one or more communication channels containing the information of the broadcast.