Counterstreaming large‐diameter electron beams in a steady‐state laboratory experiment are observed to generate transverse radiation at twice the upper‐hybrid frequency (2&ohgr;UH) with a quadrupole radiation pattern. The electromagnetic wave power density is nonlinearly enhanced over the power density obtained from a single beam–plasma system. Electromagnetic power density scales exponentially with beam energy and increases with ion mass. Weak turbulence theory can predict similar (but weaker) beam energy scaling but not the high power density, or the predominance of the 2&ohgr;UHradiation peak over the &ohgr;UHpeak. Significant noise near the upper‐hybrid and ion plasma frequencies is also measured, with normalized electrostatic wave energy densityWES/neTe≊10−2.