The beginning of radio astronomy

August 24th, 2012, Published in Articles: EngineerIT

by Hans van Groenendaal, features editor, EngineerIT

In this monthly feature, Hans van de Groenendaal ZS6AKV, executive chairman of the South African Amateur Radio Development Trust (SAARDT), looks at various technologies and activities that drive amateur radio. SAARDT is dedicated to the development of amateur radio in South Africa with a special interest in the youth. The organisation is funded by donations and supports the South African Radio League and SA AMSAT.

Grote Reber’s original parabolic dish
antenna now resides on the grounds
of the National Radio Astronomy
Observatory at Green Bank,
West Virginia, alongside a
full-scale replica of Jansky’s
antenna shown here.

The Square Kilometre Array (SKA) awarded to South Africa has created a renewed interest amongst radio amateurs in radio astronomy. Not long after Karl Guthe Jansky discovered radio signals from the Milky Way in 1931, radio amateurs became involved and did some major pioneering work. Undoubtedly the most outstanding contribution to radio astronomy by a radio amateur was from Grote Reber. He held the callsign W9GFZ. Born in the USA in 1911, he became a radio amateur at the age of 16 and won many awards for his amateur radio activity. Eventually he decided that were “no more worlds to conquer in radio” but reading about Jansky’s discovery of radio emissions from the Milky Way a new bug bit him: radio astronomy.

In 1937 he drew up plans to build a large parabolic reflector. He asked the American Bridge Company for a quote but when they told him that it would cost $7000 to build the telescope he decided to construct the antenna himself. With the help of two friends, he built a reflector out of galvanised sheet metal and wooden beams. The mirror was 9,5 m in diameter with a focal length of 6 m.

Working at higher frequencies than Jansky – 5 GHz instead of 21 MHz – he began to spot emission peaks in the Milky Way. These were the intense radio sources in the constellations Cygnus, Taurus, and Cassiopeia. In 1938 he made several improvements to his telescope using reducing the frequency to 900 MHz but he was still unsuccessful. A year later he decreased the frequency to 160 MHz and was finally successful.

Original antenna (Credit NRO).

Once Reber had an operational telescope he set out to construct a radio map of the Milky Way. First he confirmed Jansky’s claim that the static was strongest at the constellation Sagittarius, the centre of the universe. He also detected strong signals from other constellations, namely Cygnus, Cassiopeia, Canis Major, and Puppis. He published his initial findings in the proceedings of the Institute of Radio Engineers. He also tried to get astronomers interested in radio waves and submitted his paper to the Astrophysical Journal, but there was no one qualified to review the paper. Eventually the editor of the journal decided to publish the paper without a review in June 1940.

In 1943 he started to explore the sun and found strong radio signals. This discovery had already been (accidentally) made by the British a year earlier but had remained a military secret until after World War II. He completed the first radio map of the galaxy in 1944, based on over 200 chart recordings. He also noted that radio waves could penetrate the interstellar dust that blocks the view of the Milky Way. This was an important improvement over visual inspections of the universe.

Grote Reber listening to radio signals from
space. (Picture credit Cosmology).

For nearly a decade he worked alone in his backyard as America’s only radio astronomer. However, once his findings were circulated among astronomers and once World War II was over, interest in the field began to grow. Reber stopped his operations in Wheaton in 1947 and moved his telescope to the United States Bureau of Standards. In 1951 he moved to Hawaii to work in an area that had less man-made radio interference. He left his original telescope behind and it was moved in 1960 to the National Radio Astronomy Observatory in Green Bank, West Virginia, where it is still on public display.

In 1954 he moved to Tasmania, off the coast of southern Australia, to be closer to the south magnetic pole where the Earth’s ionosphere was the weakest and, therefore, radio waves were the strongest. Even in Tasmania Reber’s work was still hindered by the ionosphere. In 1985 Reber used a mission of the space shuttle Challenger to his advantage. On 4 August 1985 when Challenger was over Reber’s telescope in Hobart, Australia, the shuttle released a quarter ton of fuel to create a hole in the ionosphere for a few hours. Through this hole Reber was able to find cosmic radiation at a wavelength of 1,7 MHz, which was the first time radio waves of this frequency from space had been recorded.

Reber’s next project took him to the other end of the earth. He took advantage of a solar minimum of 1986 and 1987 to try to map the northern sky at 2 MHz to match his southern sky map at that same frequency.

Reber’s story illustrates again how powerful an early start in amateur radio is to create a career interest and a path to the science and engineering fields. Grote Reber died in Tasmania on 20 December, 2002, just two days before his 91st birthday.

Related Articles

  • South African Government COVID-19 Corona Virus Resource Portal
  • Now Media acquires EngineerIT and Energize from EE Publishers
  • Printed electronics: The defining trends in 2019
  • Charlie and the (fully-automated) Chocolate Factory
  • SANSA app calculates best HF communication channel