page_title: Blaw-Knox tower
hierarchical_section_title: Blaw-Knox tower
caption_attribution_description: English: Transmitter towers of AM radio station WBT just south of Uptown Charlotte, NC. These distinctive diamond-shaped towers were constructed in 1932 by the Blaw-Knox Co. and are called Blaw-Knox towers. The purpose of the diamond-cantilever shape was to improve the horizontal radiation pattern to reduce fading, and also to make the tower rigid to shear stress so that it only needs one set of guy-lines, attached at its broad "waist". In the 1930s, multiple sets of guy lines, as are used on modern "thin" antennas, tended to interfere with the radiation pattern of the antenna.
context_page_description: The Blaw-Knox company was a manufacturer of steel structures and construction equipment based in Pittsburgh, Pennsylvania. The company is today best known for its radio towers, most of which were constructed during the 1930s in the United States. Although Blaw-Knox built many kinds of towers, the term Blaw-Knox tower usually refers to the company's unusual "diamond cantilever" design, which is stabilized by guy wires attached only at the vertical center of the mast, where its cross-section is widest. During the 1930s AM radio broadcasting stations adopted single mast radiator antennas, and the Blaw-Knox design was the first type used. A 1942 advertisement claims that 70% of all radio towers in the United States at the time were built by Blaw-Knox.
  The distinctive diamond-shaped towers became an icon of early radio. Several are listed on the United States National Register of Historic Places, the distinctive diamond antenna design has been incorporated into logos of various organizations related to radio and a very large replica of the WSM Blaw-Knox tower has been built into the Country Music Hall of Fame and Museum.
context_section_description: The Blaw-Knox company was a manufacturer of steel structures and construction equipment based in Pittsburgh, Pennsylvania. The company is today best known for its radio towers, most of which were constructed during the 1930s in the United States. Although Blaw-Knox built many kinds of towers, the term Blaw-Knox tower (or radiator) usually refers to the company's unusual "diamond cantilever" design, which is stabilized by guy wires attached only at the vertical center of the mast, where its cross-section is widest. During the 1930s AM radio broadcasting stations adopted single mast radiator antennas, and the Blaw-Knox design was the first type used. A 1942 advertisement claims that 70% of all radio towers in the United States at the time were built by Blaw-Knox.
  The distinctive diamond-shaped towers became an icon of early radio. Several are listed on the United States National Register of Historic Places, the distinctive diamond antenna design has been incorporated into logos of various organizations related to radio and a very large (scale) replica of the WSM (AM) Blaw-Knox tower has been built into the Country Music Hall of Fame and Museum.
caption: WBT's 428 ft (130 m) transmitter towers just south of uptown Charlotte, North Carolina.
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