Quadrature modulation as an alternative of AM in broadcasting and communications

The paper proposed a new broadcasting system in the LW, MW and SW bands, based not on the traditional amplitude modulation (AM), but on the quadrature modulation (QAM). It is shown that at the equal transmitted power the efficiency of transmitters with QAM and their range increase by several times. The receivers are recommended to carry on the heterodyne scheme with phase-locked loop (PLL). They provide better selectivity, noise immunity and signal quality demodulation.