improvements in estimates of the optical depth to CMB photons and, thus, would help to break existing degeneracies in CMB measurements between the optical depth and properties of the primordial matter density power spectrum [@2006PhRvD..74l3507T].

![ \[f\_edges\_photos\] EDGES deployed at Mileura Station in Western Australia. The left panel shows the full antenna and ground screen in the foreground and the analog-to-digital conversion and data acquisition module in the background. The right panel is a close-up view of the amplifier and switching module connected directly to the antenna (through the balun).](f1_color.eps){width="20pc"}

For these reasons, several efforts are underway to make precise measurements of the radio spectrum below $\nu<200$ MHz ($z>6$). In this paper, we report on the initial results of the Experiment to Detect the Global EOR Signature (EDGES). In § \[s\_edges\_method\], we describe the specific approach used for EDGES to address the issue of separating the redshifted 21 signal from the foreground emission. We then give an overview of the EDGES system in § \[s\_edges\_system\], followed by the results of the first observing campaign with the system in § \[s\_edges\_results\], along with a discussion of the implications for future single-antenna measurements.

Method {#s_edges_method}
======

In principle, the global brightness temperature 