By the mid-1950s the latest design of aerial from PO was becoming standard. This design was known as Rhombic (diamond shaped). Rhombic aerials used four masts for support, each mast being around 150ft high. The masts were made of twelve, triangular-shaped, galvanised steel sections bolted together. A pair of Rhombic aerials (one at the top of the masts and another half way down) could cover the whole of the short wave band and were directional, having a beam width of about 10 degrees.