Today’s Whimsy
There was a young fellow named Dwight
Whose skill with a key was sight.
He sent smooth ripplin’ dits
That gave slower guys fits
As he talked with his friends day and night.
When This Ham Sets About to Build an Antenna, He Builds a REAL Antenna
How It Started John Kraus, W8JK, started with tin can and string telephones and a crystal radio that he built. At age 10, in 1920, when radio broadcasting was in its infancy, he was able to receive WWJ in Detroit, from his home in Ann Arbor, MI. He went on to a tube type receiver, and once stayed up past midnight to hear KFI, Los Angeles. To a young man, it was magical. He was hooked, just as many of us were.
John Kraus, W8JK, started with tin can and string telephones and a crystal radio that he built. At age 10, in 1920, when radio broadcasting was in its infancy, he was able to receive WWJ in Detroit, from his home in Ann Arbor, MI. He went on to a tube type receiver, and once stayed up past midnight to hear KFI, Los Angeles. To a young man, it was magical. He was hooked, just as many of us were.
John went on to earn a PhD in physics at University of Michigan in 1933. His eventual career interest was antennas, and he made many important contributions to the field including writing the most widely accepted advanced text on the subject. He became an antenna man among antenna men.
The Antenna Bug Bites
In 1937, during the Great Depression, John had been working on research projects at University of Michigan and other places, along with Grote Reber of backyard dish and stellar radio source fame. About this time, it appears that the antenna bug really started to bite John.
He made contact with ON4CSL, Carroll Stegall, a missionary in the Belgian Congo (later Zaire, later still The Democratic Republic of the Congo) in central Africa. Carroll was delighted to have a conduit for messages back home, which had been taking two months by mail. John and Caroll began a series of regular contacts. Sometimes the contacts were easy, and sometimes they were difficult. John started looking for a better antenna.
He read an article in the Proceedings of the IRE about close spaced antennas, and promptly started designing a practical antenna based on the article, which he put in place a week later on the first Saturday of January, 1937, in the cold. What he made became known as the W8JK flat top, or simply the 8JK, which he published in RADIO, a west coast ham magazine. It is simply two parallel dipoles ⅛ wave apart, fed out of phase. It has a nice low angle of radiation, and some bidirectional gain, and works well for DX. It was an instant success, generating a flood of correspondence and construction. It successfully replaced the Bruce antenna he had been using for Africa.
By 1946, John was comfortably settled in a teaching and research position at Ohio State University. In November, comments by a guest speaker caused him to speculate about the possibility of using a helix (corkscrew) as an antenna.
His initial work was in his basement, where his wife had hung the laundry. He worked his way through the bed sheets, underwear and tablecloths to reach his ham work bench. There, he wound a coil about 4 cm in diameter, 7 turns, about 15 cm long, which he fed with a 12 cm (2.5 GHz) oscillator borrowed from the university. From his junkbox, he cobbled together a small broadband detector, which revealed that the helix was highly directional, off the end. The helical antenna was born! It turned out to be circularly polarized and very broadbanded, and has since been used in many applications, including satellite antennas.
John went on to invent other antennas, including the corner reflector antenna, often used for TV reception, and what may have been the first flat panel phased array antenna which is today used for radar, so as to avoid the necessity of rotating a parabolic dish.
John Designs a REAL Antenna
At Ohio State U, John’s crowning antenna achievement was the “Big Ear” radio telescope. Look at the size of that monster! In one of his videos, he mentioned that it had 60 dB gain, a factor of 1,000,000.
On the far right of the image is a flat, tiltable RF mirror that changes the elevation angle of the telescope’s view. On the left is a huge section of a parabolic RF mirror. RF from the parabola is focused on the small structure in front of the flat reflector, and the receiving equipment is located underground, below that. Equipped with a liquid Nitrogen cooled preamplifier, the receiver can hear very faint signals. As the Earth rotates, most of the sky is visible to the telescope.
Initially, the telescope was used to do a survey of the radio sky. This cataloged over 19,000 radio sources, many of which were new, having no corresponding visible object. Later, it was used in the Search for Extra-Terrestrial Intelligence, SETI.
You can’t fool me. This was carefully described as a noble scientific search. In reality, I feel sure it was just John looking for the ultimate DX.
If ham radio sparks your curiosity, and gives you an avenue for experimenting and finding out how things work, then you may have more in common with John Kraus than you realize.
73 For Now,
Denton
W7DB