  We report on the measurement of coherent radio emission from the electron
beam sudden appearance at the Telescope Array Electron Light Source facility.
This emission was detected by four independent radio detector setups sensitive
to frequencies ranging from 50 MHz up to 12.5 GHz. We show that this phenomenon
can be understood as a special case of coherent transition radiation by
comparing the observed results with simulations. The in-nature application of
this signal is given by the emission of cosmic ray or neutrino induced particle
cascades traversing different media such as air, rock and ice.
