The most distant radio waves detected so far are known as cosmic microwave background (CMB) radiation. The CMB is the afterglow of the Big Bang and represents the oldest light in the universe. It originated when the universe became transparent to photons about 380,000 years after the Big Bang.
The CMB radiation pervades the entire observable universe and is present in the form of radio waves, among other wavelengths. It has been extensively studied by various satellite and ground-based experiments, such as the Cosmic Background Explorer (COBE), the Wilkinson Microwave Anisotropy Probe (WMAP), and the Planck satellite.
Since the CMB represents the earliest light that we can observe, it can be considered the most distant radio wave. The CMB radiation allows scientists to study the properties of the early universe and gain insights into its formation and evolution. It provides important evidence in support of the Big Bang theory and has contributed significantly to our understanding of cosmology.