What is component 4 in figure T-3?

Explicación
Component 4 is the antenna in Figure T-3. The feed line is component 1, while a transmitter, dummy load, and ground are not the numbered part at the output of the coupler.

Component 4 is the antenna in Figure T-3. The feed line is component 1, while a transmitter, dummy load, and ground are not the numbered part at the output of the coupler.