To develop a detector with an effective area large enough to observe an extensive air shower,
we studied a method of detecting radio waves generated via the transition radiation process by charged particles in an air shower. Characteristics of the radio waves were investigated using beam accelerators and radio antennas . When about 430x10^9 electrons with a kinetic energy
of 4.7 MeV crossed a titanium film into the air, the radio pulse emitted was measured using a standard dipole antenna with a bandwidth of 800 - 880 MHz. The measured pulse height at a position 1.2 m away from the source and at an angle of 5 degree from the beam axis was approximately
670 mV. It was found that the electric field strength had large angular dependence and that the polarization property was roughly consistent with the theoretical value.