While both Karl Guthe Jansky and Grote Reber played pivotal roles in the development of radio astronomy, Karl Guthe Jansky is credited with inventing the first radio telescope.

Here's why:

* Jansky's Discovery: In 1931, while working for Bell Telephone Laboratories, Jansky was tasked with investigating sources of static interference that could disrupt transatlantic radio communications. He built a rotating antenna to study the interference, and discovered a consistent signal from a source outside of the Earth. He identified this source as the center of the Milky Way galaxy, marking the beginning of radio astronomy.

* Reber's Contribution: Inspired by Jansky's work, Grote Reber built the first dedicated radio telescope in 1937. This parabolic dish antenna was more sensitive and directional than Jansky's antenna, allowing Reber to map the radio sky and make significant discoveries about the distribution of radio sources in the universe.

In summary: Jansky's invention of the first radio telescope was the groundbreaking discovery that launched the field of radio astronomy. Reber's work further advanced the technology and contributed significantly to the early development of the field.