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.