  The development of a system to detect the radio-frequency (RF) pulse
associated with extensive air showers of cosmic rays is described. This work
was performed at the CASA/MIA array in Utah, with the intention of designing
equipment that can be used in conjunction with the Auger Giant Array. A small
subset of data (less than 40 out of a total of 600 hours of running time),
taken under low-noise conditions, permitted upper limits to be placed on the
rate for pulses accompanying showers of energies around $10^{17}$ eV.
