During the WWII, the German army created the Atlantic Wall along the entire European coast, from Norway, through Denmark, the Netherlands, Belgium and France. Part of this Kammhuberlinie were overlapping radar stations, using the so-called Würzburg Riese radar antennas.
After the War, several of the antennas were confiscated by the Dutch Telecommunication service PTT. Some were brought to the radio station at Kootwijt, in East Netherlands. PTT gave one to the Dutch Association for Radio Emission from the Sun and the Milky Way (now ASTRON). On May 11, 1951, with this antenna, Lex Muller confirmed the detection of 21cm emission from atomic hydrogen in our Milky Way Galaxy six weeks after Harold Ewen found it with his feed horn at Harvard.
Horn o’Plenty Discoveries
This horn antenna was used by Harold Ewen and Edward Purcell at Harvard University to search for the 21 cm emission from neutral hydrogen in the Milky Way Galaxy. They finally detected it on March 25, 1951.
In 1950, Ewen was a physics graduate student building a receiver to detect the 21 cm line of neutral hydrogen. Purcell, his supervisor, asked for, and received, a grant of $500 from the Rumford Fund of the American Academy of Arts and Sciences for materials costs. Ewen installed the horn outside the fourth floor of the Lyman Lab at Harvard, with the waveguide leading in through the window to the receiver and recorder. In heavy rains, the horn antenna funneled water into the lab. During the winter, passing students found the horn a tempting target for snowballs.
Grote Reber in Green Bank
In the early 1960s, Grote Reber came to the NRAO in Green Bank to reassemble his radio telescope built originally in 1937 in Iliinois. Here he is with the finished telescope and its receiver tower (right).
Long Wavelength Demonstrator Array
The Long Wavelength Array is a collection of 256 antennas stationed at the Very Large Array site outside Magdalena, New Mexico. It is a low-frequency radio telescope designed to produce high-sensitivity, high-resolution images in the frequency range of 10-88 MHz. This station is one of several, giving the entire LWA project a large collecting area (up to 1 square kilometer at its lowest frequencies) spread over an array with baselines up to at least 400 km. With long wavelengths, astronomers can learn more about Dark Energy and Dark Matter, hunt for the earliest hydrogen back in the young Universe, and hunt for planets around other stars.
Amidst the Antennas of the LWA
These are the four-sided dipole antennas of the Long Wavelength Array on the site of the Very Large Array in central New Mexico. Like the VLA, the LWDA combines the views of its individual antennas into impressive radio images of the sky. Unlike the VLA, however, the LWA antennas cannot dip or turn. To image different parts of the sky, the antennas rely on sophisticated electronics, software, and their four-sided faces.
The LWA is tuned to natural radio waves that are below the range of manmade FM radio broadcast channels to observe pulsars, the Sun and its effects on the planets, and the most distant stars and galaxies in the Universe. In addition, the LWA also studies the radio-bouncing layer of our atmosphere, called the ionosphere.
First VLA Antenna Move Across Highway 60
The Very Large Array in New Mexico can be reconfigured by moving any of its 27 antennas to new positions along 40 miles of double-railed track. Some of the tracks cross the New Mexico highways, as seen during this move in the 1970s.