Antenna location at the U.S. Naval Communication Station Harold E. Holt in Exmouth, Western Australia, in 1972. This is a very low frequency (VLF) transmitter which communicates with submerged submarines. This type of antenna is called a "Trideco" or umbrella antenna. It consists of multiple steel masts which radiate radio waves, with a network of cables attached to their tops. The cables do not themselves radiate radio waves, but serve as a capacitive top-load, adding capacitance to the top of the antenna to make it more efficient. On the ground under the antenna there is an elaborate ground system called a counterpoise consisting of radial cables in a star shape suspended a few feet above the ground.
US Navy, Naval Electronics Systems Command
1972
NAVELEX 0101, 113 Fig. 3-14