AMSAT-NA Past President and ham radio satellite and digital pioneer Tom Clark, K3IO (ex-W3IWI), of Columbia, Maryland, died on September 28 after a short illness and hospital stay. An ARRL Life Member, he was 82. Clark’s accomplishments are legendary, and he left a lasting footprint in the worlds of amateur radio satellites and digital techniques.

“His long-time technical achievements, mentoring to others, and technical leadership will be missed by his many peers and friends the world over,” said Bob McGwier, N4HY.

To honor Clark, AMSAT has rebranded its upcoming annual gathering as the 2021 AMSAT Dr. Tom Clark, K3IO, Memorial Space Symposium and Annual General Meeting. It will take place on October 30 via Zoom. (AMSAT members may register to attend via AMSAT’s Membership and Event portal.) The event will be livestreamed on AMSAT’s YouTube channel.

A founding member of Tucson Amateur Packet Radio (TAPR), Clark was a co-founder of the TAPR/AMSAT DSP Project, which led to software-defined radio (SDR). He was a leader in the development of the AX.25 packet radio protocol. Clark served as AMSAT’s second President, from 1980 until 1987. He also served on the AMSAT and TAPR Boards.

In concert with McGwier, Clark developed the first amateur Digital Signal Processing (DSP) hardware, including a number of modems. He developed the uplink receivers and the spacecraft LAN (local area network) architecture used on all the Microsats (AMSAT-OSCAR 16, Dove-OSCAR 17, WEBERSAT-OSCAR 18, LUSAT-OSCAR 19, Italy-OSCAR 26, AMRAD-OSCAR 27, and TMSAT-OSCAR 31). McGwier said it was Clark who convinced him in 1985 that the future lay in DSP.

“We started the TAPR/AMSAT DSP [digital signal processing] project, and it was announced in 1987,” McGwier recounted. “We showed in our efforts that small stations with small antennas could bounce signals off the moon, and, using the power of DSP, we could see the signals in our computer displays.” This led to the software-defined transponder (SDX) for satellite work, including ARISSat and AMSAT’s Phase 3E.

Clark received a doctorate in astrogeophysics from the University of Colorado. He went on to serve as Chief of the Astronomy Branch at NASA Marshall Space Flight Center and was a Senior Scientist at NASA Goddard Space Flight Center, where he was principal investigator for the Space Very Long Baseline Interferometry (VLBI) activity there.

In 2005, Clark became the first non-Russian to be awarded a Gold Medal of the Russian Academy of Sciences for his contributions to the international VLBI network. He is a member of the 2001 class of CQ magazine’s Amateur Radio Hall of Fame.

In 2016, ARRL awarded Clark with its President’s Award, to recognize his 60 years of advancing amateur radio technology. On that occasion, McGwier said, “There would be no AMSAT to inspire all of this work without Tom Clark. Tom…saved the organization and inspired all of us to look to the future and aim for the stars.”

Clark was a Fellow of the American Geophysical Union and the International Association of Geodesy.