Ketch ketch and the yawl have two masts, with the main mast foremost; the distinction usually being that a ketch has the mizzen mast forward of the rudder post, whereas on a yawl, it is aft of the rudder post. But the balance of sail area can be an overriding characteristic. If 20% or more of the sail area is in the mizzen sail the rig would be termed a ketch. This is particularly true on center cockpit yachts. Compared to a ketch, a similar size yawl's mizzen sail is much smaller than the main, because of the limitations of the
Radio masts and towers for research to find ways to minimize the hazard that communications towers can pose to birds. There have also been instances of rare birds nesting in cell towers and thereby preventing repair work due to legislation intended to protect them. Since June 2010, Telecom operators in the USA can erect new telecom masts or towers as the government has lifted the moratorium, which was earlier placed on the issuance of permits for the construction of telecommunication towers. Radio masts and towers Radio masts and towers are, typically, tall structures designed to support antennas (also known as aerials) for telecommunications and