The predicted instability of obliquely propagating whistler waves in a plasma penetrated by an electron beam is verified in a laboratory experiment. The observations support the model for the generation of auroral hiss and compare favorably with ground and satellite observations of VLF hiss. In contrast to the conventional small-diameter laboratory beam-plasma systems the present device is large in comparison to the characteristic whistler wavelength (&lgr;?2-4 cm; beam and plasma diameter, 45 cm; length, 250 cm). Unstable whistlers can therefore propagate and grow oblique to the beam over many wavelengths before encountering the plasma boundaries. When a cold (1 eV), energetic (40 eV), low-density (nb?108 cm-3) electron beam is injected along the magnetic field (B0=75G) into an initially cold (kTe?1/4 eV), dense (ne?1010 cm-3) background plasma, the spontaneous emission of broadband RF noise ranging from the lower hybrid frequency &ohgr;lh to the electron cyclotron frequency &ohgr;e is observed. By performing narrowband two-dimensional cross-correlation measurements between two small antennas the RF noise is identified from its dispersion characteristics &ohgr; (k) as whistler waves propagating near the oblique resonance angle ϑ=arccos (&ohgr;/&ohgr;e). The parallel phase velocity is close to the beam velocity (&ohgr;/k≲&ugr;b). Although the instability amplitude is far above the thermal noise level, it is not large enough to give rise to significant nonlinear effects. The instability saturates when the higher-frequency short-wavelength electrostatic instability near the electron plasma frequency (&ohgr;p2≫&ohgr;e2) forms a plateau in the beam distribution. Time- and space-resolved electron pitch angle distribution function measurements are performed. The propagation of the whistlers out of the instability region and refraction into electromagnetic whistlers are observed. Finally, in the unstable system, coherent whistler waves are launched from a small antenna. In the direction opposing the beam the wave energy diverges along the resonance cone of angle ϑe=arcsin (&ohgr;/&ohgr;e), just as occurs in a stable plasma. But in the direction of the beam an unstable oblique whistler wave with a well-defined wave number is excited. The wave normal is at an angle ϑ=¿arccos (&ohgr;/&ohgr;e) with respect to B0, and the amplitude increases away from the source at the complementary angle. Thus out of the broad k vector spectrum excited by a point source the most unstable mode of the system predominates. These observations are relevant to the radiation characteristics of satellite antennas in regions of electron precipitation.