When temporally modulated, the gyrophase-bunched sheet beams of electrons that emanate from magnetized double layers may produce electromagnetic radiation with high efficiencies in narrow frequency bands Δf~200 Hz, the electromagnetic waves being broadcast in the north-south (constant longitude) direction. For the modulated-beam mechanism, efficiencies, power levels, and polarizations are estimated. It is found that of the order of 160 auroral arcs that are each 103 km long are necessary to produce 109 W of radiation. Beam modulation mechanisms, auroral zone measurement techniques, and electromagnetic wave reflection are discussed, and a laboratory techniques, and electromagnetic wave reflection are discussed, and a laboratory experiment to study the modulated-beam emission mechanism is outlined. ¿ American Geophysical Union 1988