First Space Application of Radio

While HF signals (which lie between 3 and 30 MHz) are much lower in frequency than today’s modern satellite links, the principle is nevertheless the same as for the ground segment. Private individuals and experienced radio hobbyists (called radio amateurs or hams) helped develop radio communications through the medium of amateur radio communication (also called ham radio) and radio astronomy. This author spent many hours as a teenager, college student, and young engineer using the international Morse code to meet fellow amateurs around the world. (International Morse code differs from the original American Morse code because it composes letters with long and short on radio transmissions rather than sequences of clicks of DC current over telegraph wires.) Starting in the 1920s, amateurs were granted key
status in the U.S. domestic regulations and later international regulations as well.

They developed their own equipment and antenna systems, and moved the technology from the low frequencies up to the bands close to those of modern satellites.

The first indication of a connection between radio and space came in 1922 when Karl Jansky, a young electrical engineer at Bell Laboratories, was investigating the various sources of noise that hinder long-distance radio communication. While most of the emitters he identified were due to terrestrial sources such as electrical machinery and thunderstorms, there was one unidentified source that appeared and disappeared on a daily basis. The clue as to the celestial nature of this source was the fact that it appeared four minutes earlier every day. From the standpoint of an astronomer, this indicated that the source was extraterrestrial. Karl Janskys announcement of the source as in the direction of the center of the Milky Way Galaxy was reported on May 5, 1933, on the front page of the New York Times.

Most early radio installations looked more like broadcasting sites than earth stations. However, it was an amateur radio operator by the name of Grote Reber who built the first operating parabolic reflector antenna. (The reflector is parabolic in cross section, producing a surface called a paraboloid.

However, the term parabola is more popular, probably because it is easier to say.) Shown in Figure 1.3 is the 10m (32 ft) wonder he created to explore the radio sky. Reber built this first model himself literally in his own backyard, and made his first discoveries of cosmic radio emissions in 1939. After continued measurement and exploration of celestial radio sources, he published the first survey of the sky at radio wavelengths in 1942 in the Proceedings of the Institute of Radio Engineers.