Most mast radiators are built as guyed masts. Steel lattice masts of triangular cross-section are the most common type. Square lattice masts and tubular masts are also sometimes used. To ensure that the tower is a continuous conductor, the tower's structural sections are electrically bonded at the joints by short copper jumpers which are soldered to each side or "fusion" (arc) welds across the mating flanges. Base-fed masts, the most common type, must be insulated from the ground. At its base, the mast is usually mounted on a thick ceramic insulator, which has the compressive strength to support the tower's weight and the dielectric strength to withstand the high voltage applied by the transmitter. The RF power to drive the antenna is supplied by a matching network, usually housed in an antenna tuning hut next to the mast, and the cable supplying the current is simply bolted to the tower. The actual transmitter is usually located in a separate building, which supplies RF power to the antenna tuning hut via a transmission line. To keep it upright the mast has tensioned guy wires attached, usually in sets of 3 at 120° angles, which are anchored to the ground usually with concrete anchors. Multiple sets of guys (from 2 to 5) at different levels are used to make the tower rigid against buckling. The guy lines have strain insulators (Johnny balls) inserted, usually at the top near the attachment point to the mast, to insulate the conductive cable from the mast, preventing the high voltage on the tower from reaching the ground. For more information, be in touch with us