T-antenna

A T-antenna, T-aerial, flat-top antenna, or top-hat antenna is a vertically polarised simple wire radio antenna used in the VLF, LF, MF and shortwave bands. T-antennas are widely used as transmitting antennas for amateur radio stations,long wave and medium wave broadcasting stations. They are also used as receiving antennas for shortwave listening.

The antenna consists of one or more horizontal wires suspended between two supporting radio masts or buildings and insulated from them at the ends. A vertical wire is connected to the center of the horizontal wires and hangs down close to the ground, connected to the transmitter or receiver. Combined, the two sections form a 'T' shape, hence the name. The transmitter power is applied, or the receiver is connected, between the bottom of the vertical wire and a ground connection.

The T-antenna functions as a monopole antenna with capacitive top-loading; other antennas in this category include the inverted-L, umbrella, delta, and triatic antennas. It was invented during the first decades of radio, in the wireless telegraphy era, before 1920.