What does “EME” stand for in the context of amateur radio?

“EME” stands for Earth-Moon-Earth communication, which refers to a mode of contact in amateur radio where signals are transmitted from Earth to the Moon and back to Earth. This technique takes advantage of the Moon as a passive reflector of radio waves. Radio operators engage in EME communications to achieve long-distance contact that would be impractical using direct line-of-sight methods due to the curvature of the Earth or other obstacles.

In this mode of communication, radio signals are transmitted at high power levels to reach the Moon. The signals are then reflected off its surface and back towards Earth, where they can be received by operators positioned thousands of kilometers away. EME communication is particularly popular among operators who enjoy the technical challenges of long-distance communications and often involves the use of specialized equipment designed for high-frequency operation and digital signal processing.

Other choices represent different concepts: Emergency Mobile Equipment suggests equipment for emergency use, Extended Modulation Equipment refers to modulation techniques, and Electromagnetic Emission relates to the radiation of electromagnetic waves. While they pertain to facets of radio and telecommunication, they do not define the specific practice of using the Moon as a communication relay, which is the essence of EME.