The sources of ultra-high energy cosmic rays have been elusive despite decades of research after their discovery. Part of the problem is the insufficient sensitivity to the particle mass provide by current detectors. I will given an introduction of radio detection of air showers, which may help to provide better sensitive experiments. Also, detecting the neutrinos corresponding to their cosmic ray counterparts could provide the key to finding the sources. I will introduce radio detection of neutrinos in ice with a special emphasis on the Radio Neutrino Observatory in Greenland (RNO-G). RNO-G is currently under construction and will improve a factor of 10 over existing EeV neutrino experiments and promises to the discovery parameter space.