  We present first measurements by MAYBE of microwave emission from an electron
beam induced air plasma, performed at the electron Van de Graaff facility of
the Argonne National Laboratory. Coherent radio Cherenkov, a major background
in a previous beam experiment, is not produced by the 3 MeV beam, which
simplifies the interpretation of the data. Radio emission is studied over a
wide range of frequencies between 3 and 12 GHz. This measurement provides
further insight on microwave emission from extensive air showers as a novel
detection technique for Ultra-High Energy Cosmic Rays.
