The radio telescope invention is accredited to Kari Guthe Jansky. A radio telescope is basically a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources (i.e., moon, stars, planets, etc.) The field of study is called Radio Astronomy and studies the radio frequency portion of the electromagnetic spectrum (E.M.). Traditional telescopes study these same astronomical objects by analyzing the light wave portion of the electromagnetic spectrum.
Since radio waves are at the lower frequency and relative weaker range of the EM spectrum, they are collected and amplified by the radio telescope antenna and receiver. These waves can then be analyzed. The general wavelength range of these waves are from 1 millimeter to 10 meters long. Therefore, we usually refer to radio waves in terms of their frequencies instead of their corresponding wavelengths. This is also why radio telescopes are the world largest telescopes with the most sensitive receivers.
Early radio telescopes had a serious limitation in that they had to be tuned to one specific frequency. With vast improvements in modern electronic technology, radio receivers and computers can divide the frequency band into several thousand separate channels that may range from over tens to hundreds of megahertz. This modern improvement in radio telescope technology provided a great advantage when compared to optical telescopes. Another advantage is that radio telescopes can be used both day and night.
Radio telescopes like the Long Wavelength Array, seen here, do not need accurate dish surfaces to detect radio waves from space. These use dipole antennas in a cross-shape.
National Radio Astronomy Observatory. What are Radio Telescopes? (2022).