More than 100 years after the discovery of cosmic rays we still know little about the origin of the most energetic particles in the universe. These cosmic particles are mainly atomic nuclei which are accelerated by nature to energies far beyond the reach of human-made accelerators. The highest energy particles seem to originate from distant galaxies, but neither their sources are known nor are the most energetic sources in our galaxy, the Milky Way. To solve these questions, on the one hand, more accurate measurements of the energy-dependent mass composition of the cosmic rays is required. On the other hand, the search for neutral particles at the highest energy, in particular neutrinos, can provide a direct discovery of the sources. In contrast to charged particles, neutral particles are not deflected by magnetic fields and point back to their origin. In the last years, digital antenna arrays have become a competitive alternative for cosmic rays above 10^17 eV. By complementing existing cosmic-ray observatories, antennas can boost the total measurement accuracy. At the same time, radio detectors are the most promising technique for the search for ultra-high-energy neutrinos. ... mehrEither way, the radio technique can be the key to solve this long-standing mystery of astroparticle physics. This talk will provide an overview on existing and future radio experiments for cosmic rays and neutrinos.