To simulate some of the major physical processes occurring in pulsars, we performed experiments using a relativistic electron beam propatating helically through a magnetized plasma. Microwave radiation with λ≈1 cm emerged when the predicted resonance conditions were satisfied. Power exceeded 1 MW and radiation lasted as long as the electron beam pulse. The spectrum, harmonics, power and scalings were consistent with a model of coherent curvature radiation from electrons which are bunched by a beam-plasma streaming instability. Brightness temperature was ∼1020 degrees. Polarization was that of single-particle emission, but with some evidence for diffraction patterns due to the beam bunches themselves. The Razin effect does not apply to our experiments and was not observed. The fundamental two-step process of electrostatic bunching followed by curvature emission describes well all our results.