The moon is a terrible reflector of radio waves. It absorbs most of what hits it, returns only a whisper, and keeps moving the whole time. Amateurs have been bouncing signals off it for more than 70 years anyway.
The idea dates to 1940, when British engineer W.J. Bray proposed that a microwave signal could be transmitted to the moon and received back on Earth. After World War II, the U.S. Army Signal Corps decided to try it. On January 10, 1946, at 11:58 a.m. local time, a team at Fort Monmouth, New Jersey — code-named Project Diana and led by Lt. Colonel John DeWitt, W4ERI — detected the first echoes of its own 111.5 MHz radar signal returning from the moon. A Hungarian team led by physicist Zoltan Bay repeated the feat less than a month later, on February 6.
Project Diana was a military experiment, but it proved two things that changed radio forever: signals could penetrate the ionosphere, and the moon could serve as a passive reflector. The military explored the idea through the 1950s — including the secret PAMOR eavesdropping program and the Navy’s Communication Moon Relay, which linked Hawaii and Washington, D.C. via a teletype path off the lunar surface — before abandoning EME to the coming communications satellites in the early 1960s.
Amateurs got there anyway, and never left. In 1953, W4AO and W3GKP detected their first lunar echoes on 144 MHz. Then in July 1960, W6HB and W1FZJ completed the first amateur two-way EME contact, on 1296 MHz. The milestones fell fast after that: the first 144 MHz contact between the U.S. and Europe (W6DNG and OH1NL) in April 1964, the first on 432 MHz (KP4BPZ and W1BU) that May, and by the early 1970s, EME contacts on 50 MHz and 2304 MHz.
Why do it? The Earth-Moon-Earth path offers something no ionospheric band can: a reliable, schedulable route between any two points on Earth that can see the moon at the same time. The catch is path loss — well over 250 dB on the higher bands — which is why moonbouncers historically ran big dishes, high power, and the best low-noise preamps money could buy.
The digital era democratized the mode. When Joe Taylor, K1JT, released the WSJT weak-signal software suite in 2001, DSP decoding let stations complete EME contacts with signals buried far below the noise — no more kilowatt amplifiers and acre-sized arrays required. Today, EME contacts have been made on every amateur band from 28 MHz to 47 GHz, and moonbounce DXCC and Worked All States awards hang in shacks around the world.
Project Diana proved the path in 1946. Eight decades later, on any clear night, someone is still out there pointing an antenna at the moon and waiting for the echo.