Q.When the modulation percentage is 75% an AM transmitter produces 12 kW, what would be the percentage power saving if the carrier and one of the side bands were suppressed before the transmission took place?

In single-sideband suppressed-carrier (SSB-SC) transmission only one sideband is sent, so the power actually transmitted is the power in one sideband; the saving is the rest of the total po …

[!TLDR]

Here $P_C = 12$ kW gives $P_T = 15.375$ kW and one sideband = 1.6875 kW; suppressing the carrier and one sideband saves $(15.375-1.6875)/15.375 \approx 89\%$.

This is a classic Karnataka II PUC Electronics power-relations problem. When the carrier and one sideband are suppressed (SSB-SC), only a single sideband is actually transmitted, so the transmitted power drops to the power in one sideband. First find the total power and the sideband powers from the carrier power $P_C = 12$ kW at $m_a = 0.75$:

$P_T = P_C\left(1 + \frac{m_a^2}{2}\right) = 12\times10^3\left(1 + \frac{(0.75)^2}{2}\right) = 15.375\ \text{kW}$ …