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ARRL Special Bulletin ARLX014 (2021)

ARLX014 Past AMSAT President and Director, and Amateur Satellite
Pioneer Tom Clark, K3IO (SK)

QST de W1AW  
Special Bulletin 14  ARLX014
From ARRL Headquarters  
Newington CT  October 1, 2021
To all radio amateurs 

ARLX014 Past AMSAT President and Director, and Amateur Satellite
Pioneer Tom Clark, K3IO (SK)

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

"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 at, .) 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,
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.


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