Abstract
The consmological Dark Age and Epoch of Reionization reflect the last gap in our ‘historical record’ since the Big Bang. There are few data available with which to constrain theory. The redshifted 21 cm hyperfine transition of Hydrogon is potentially a unique tracer of the then rapidly evolving intergalactic medium and indicator of what objects populated the early Universe. New generations of instrumentation, both interferometer arrays and single antennas, are in development for detection of The Hydrogen line below 200 MHz, via the angular power spectrum of sky brightness and sky-averaged power. Mass deployments of dipole antennas enable assembly of very large collecting areas at relatively low cost. However, there are trade offs where the large numbers of elements, wide fields of view, tight calibration tolerances, and bright foreground emission demand use of new advanced algorithms and impose potentially extreme computational costs. I will discuss recent limits on reionization, aeeays and techniques in development, and the progression of instruments anticipated in this decade.