Flattop antenna 1912

A triatic or "flattop" antenna, a type of "inverted L" wire antenna used in high power very low frequency transmitting stations, particularly the longwave radiotelegraphy stations during the wireless era up until the mid 1920s. It consists of multiple wires (from 7 to 30) extending from the transmitter in the building up to a series of tall steel towers where they ran parallel to the ground for distances up to a mile. It was used for transoceanic transmitters at frequencies from 300 kHz to 20 kHz. Antennas at these frequencies are very electrically short, a small fraction of a wavelength high, and therefore inefficient radiators. It functioned as a capacitively loaded monopole antenna; the vertical section was the main radiator, while the horizontal section acted as a capacitive top load, increasing the current in the vertical section to increase the radiated power. There is a ground system consisting of radial buried cables under the antenna, connected to the other side of the feedline.