Air coupling occurs when the transmitter's signal travels through open air and is received directly by the receiver. What is a consequence of this phenomenon?

• A. The signal travels through underground cables to the receiver.
• B. The receiver picks up only the intended utility signal.
• C. The receiver is shielded from noise.
• D. The transmitter's signal travels through open air and is received directly by the receiver.

Answer: (D)

Air coupling means the transmitter’s RF energy is radiated into the surrounding air and can be picked up by the receiver through that open path. The consequence is that the receiver directly receives the transmitter’s signal via the air, without any physical conductor linking them. This is why the energy can be detected even when there’s no underground or direct cable connection. It also helps explain why air-coupled signals can introduce unwanted readings or interference if other gear picks up the same energy. The other options don’t fit because they describe underground paths, exclusive reception of the intended signal, or shielding from noise, which aren’t characteristics of air coupling.