Amateur Spread Spectrum
Paul Rinaldo, firstname.lastname@example.org
Hal Feinstein, email@example.com
André Kesteloot, firstname.lastname@example.org
The use of spread spectrum communications began in the Amateur Radio Service in
March 1981 when the FCC issued a Special Temporary Authority (STA) to AMRAD.
W4RI and K2SZE made the premiere HF contact using frequency hopping. WA3ZXW,
N4EZV, WB5MMB and K8MMO were also involved in these early experiments. A joint
FCC-AMRAD 'fox hunt' demonstrated that spread spectrum stations could be located
with direction-finding techniques. N4ICK became involved later, beginning in 1986.
At AMRAD's urging, in 1985 the FCC amended Part 97 of its Rules to permit regular
spread spectrum communications in the Amateur Radio Service with certain restrictions as
to spreading methods and limited to frequencies above 420 MHz. These restrictions have
been the subject of controversy within the Amateur Radio community ever since, some
desiring to remove them entirely including permitting spread spectrum operation on all
amateur bands, others wishing to tighten them. STAs subsequently have been issued to
K6KGS and a number of amateur stations on the West Coast, and in 1996 to the Tucson
Amateur Packet Radio Corporation (TAPR), both of which allow operation above 50
MHz with unrestricted spreading codes. In 1996, the American Radio Relay League
(ARRL) petitioned the FCC to permit other spreading sequences, require automatic power
control when transmitting at powers above 1 watt, while keeping the lowest operating
frequency at 420 MHz. The FCC has issued a Notice of Proposed Rule Making and is
expected to decide on rule changes during 1997-98.
What is Spread Spectrum?
Spread spectrum is a technique to reduce the power density of a radio transmission by
spreading its signal over a wide band of frequencies, at least 10 times the information rate
and usually much higher. Under some conditions, reduction of power density permits
greater spectrum sharing opportunities than using the traditional access method frequency-
division multiple access (FDMA) or even time-division multiple access (TDMA). As the
receiving system must despread the spread spectrum signal just the opposite from how it
was originally spread and in exact synchronization, there is the added advantage of
rejection of interference or jamming and immunity from frequency-selective fading. Some
modern cellular and other systems use a form of spread spectrum called code-division
multiple access (CDMA).
How Do I Learn More?
The best basic information on amateur spread spectrum can be found in The ARRL Spread
Spectrum Sourcebook, authored by AMRAD, N4ICK editor, and published by the ARRL.
Check their Web pages at http://www.arrl.org. Spread spectrum information also is found
in the AMRAD Newsletter mailed to members.
How Can I Get Involved?
AMRAD welcomes participation in new developments in amateur spread spectrum. This
includes, but is not limited to:
- construction and testing of new spread spectrum radios
- experimenting with spectrum sharing techniques
- mainstreaming the use of spread spectrum in the amateur bands
- writing for the AMRAD Newsletter
- contibuting to future editions of The ARRL Spread Spectrum Sourcebook
- supporting the modernization of Part 97 spread spectrum rules
The AMRAD Webmaster
Last modified: Sat Sep 22 21:50:04 EDT 2007