The cosmological timing of the Dark Ages (the epoch before the formation of the first collapsed objects) and the re-ionization epoch (EoR; the epoch when the intergalactic medium is ionized) has remained poorly constrained. A direct approach to constraining the Dark Ages and the EoR may be provided by the detection of the 21cm (1420 MHz) hyperfine line of neutral hydrogen (HI) redshifted to frequencies below 200 MHz. This thesis presents the theoretical and practical search for a radioquiet site to observe the signal, including the development of an automatic site testing instrument. The design, prototype and field testing of an ultra-wideband antenna. And the implementation of a Fourier-transform spectrometer to perform field observations at Guadalupe Island.