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The concept of Earth-Moon-Earth (EME) communication has fascinated amateur radio enthusiasts for decades. Reflecting a signal off the lunar surface and back to Earth is no small feat, requiring careful consideration of power, equipment, and technique. While traditional EME setups often rely on substantial power outputs, remarkable experiments have shown that successful communication is possible even with as little as 1 watt of transmitter power.
Achieving EME communication with such limited power presents a unique challenge. The primary hurdle lies in the vast distance between the Earth and the Moon—approximately 384,000 kilometers. This distance causes a signal to weaken significantly, necessitating highly optimized equipment and methods to ensure success. Nevertheless, a combination of advanced digital signal processing, high-gain antennas, and skilled operation has allowed several enthusiasts to demonstrate the feasibility of 1-watt EME communication.
A critical component of any EME setup is the antenna system. High-gain antennas, such as large parabolic dishes or long Yagi arrays, are essential for both transmitting and receiving signals. These antennas focus the transmitted power into a narrow beam, ensuring as much energy as possible reaches the Moon. They also improve the reception of the faint signal that returns after reflecting off the lunar surface. Large setups, such as the 32-Yagi array used by Dave W5UN, have proven capable of detecting signals transmitted with as little as 1 watt.
Low-noise receivers play an equally vital role. A well-designed system with low-noise amplifiers at the antenna feed point significantly enhances the ability to detect weak signals. Modern digital signal processing tools, such as those found in software-defined radios (SDRs), further improve the capability to extract meaningful communication from the noise. Digital modes like JT65, JT4, and Q65, specifically designed for weak-signal communication, are indispensable for decoding these faint transmissions. These modes can detect signals that are below the noise floor, making them ideal for low-power EME experiments.
Several pioneers in the field have demonstrated the potential of 1-watt EME communication through real-world experiments. Dave W5UN’s station, equipped with his impressive 32-Yagi array and advanced digital decoding tools, has successfully received signals from low-power transmitters. Similarly, Al Katz, known as K2UYH, has logged numerous QSOs (two-way contacts) with stations running 1 watt or less. Al’s work underscores the importance of high-performance receiving setups in enabling such communication.
Another remarkable example comes from Doug McArthur, VK3UM, who specialized in portable EME systems. Using a parabolic dish just three meters in diameter and only 1 watt of power, Doug managed to establish successful EME contacts on the 1296 MHz band. His work demonstrated that compact, low-power systems could be viable for EME communication, inspiring other operators to attempt similar projects.
In Europe, Jan DL9KR achieved impressive results with CW (continuous wave) signals, demonstrating the enduring relevance of manual decoding and operator skill. His ability to decode transmissions from stations using less than 2 watts of power highlights the synergy between human expertise and optimized equipment. This achievement stands as a testament to the ingenuity and dedication of the amateur radio community.
The Moon-Net community, a collective of EME enthusiasts, has become a hub for sharing low-power success stories. Members frequently report QSOs achieved with 1 watt of power using digital modes. One notable case involved a station in Europe successfully contacting another in the United States, proving that transatlantic EME communication is achievable with minimal power under optimal conditions. These stories foster collaboration and inspire newcomers to explore the field.
Leif SM5BSZ’s experiments with advanced DSP software add another dimension to the story of low-power EME. Leif demonstrated that software advancements could make up for hardware limitations, enabling the decoding of 1-watt signals even under suboptimal conditions. His contributions have been instrumental in expanding the accessibility of EME to a broader audience.
Organizations like HB9Q maintain detailed databases of EME activity, including low-power achievements. These records serve as valuable resources for operators seeking to validate their QSOs or learn from others. HB9Q’s highly sensitive receiving station, featuring a 10-meter parabolic dish, has played a crucial role in enabling contacts with stations transmitting at just 1 watt.
Beyond individual accomplishments, low-power EME experiments have become an avenue for educational outreach and innovation. Schools and amateur radio clubs often use 1-watt EME projects to teach students about radio propagation, space science, and weak-signal communication. Contests and awards, such as the ARRL EME Contest or the DUBUS Award, further motivate operators to push the limits of their equipment and skills.
The pursuit of 1-watt EME communication exemplifies the spirit of amateur radio—combining technical ingenuity, experimentation, and collaboration. By leveraging modern digital technologies, precise equipment, and a deep understanding of radio wave behavior, operators around the world have turned a seemingly impossible goal into an attainable reality. Their work continues to inspire and challenge new generations of radio enthusiasts, proving that even with limited power, the Moon remains within reach.