February 1973 Popular Electronics
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
In 1971 the International
Telecommunications Union (ITU), convened a meeting dubbed the
Administrative Radio Conference for Space Telecommunications (WARC-ST). The
ITU was a specialized agency of the United Nations for telecommunications, with
a membership of 140 nations. Satellite communications was barely a decade old, but
already the need for international agreements on spectrum usage had become very
apparent. Prior to the 1971 meeting, there was the 1963 Extraordinary Administrative
Radio Conference held in Geneva, Switzerland. Amateur radio had its presence in
the game acknowledged with further allocations for its members'
six had been flown already. As of this writing there are about 20 OSCAR satellites still in operation.
Amateur satellites take many forms these days, including the newest trend in
CubeSat platforms with a well-defined
set of specifications on dimensions (10 cm per side) and mass (≤1.33 kg, 2.9 lb) per cube. Launches are provided on a space available basis at a substantially
International Regulations That Will Affect Extraterrestrial Communications
Some of the 750 delegates from 101 countries who attended the
space telecommunications conference in Geneva under auspices of International Telecommunication
By Stanley Leinwoll
On January 1, 1973, a revised set of Radio Regulations assigning frequencies
to all forms of space communication went into effect. Hammered out by some 750 delegates
from 101 member nations of the International Telecommunications Union (ITU) in the
summer of 1971, the Regulations will affect all space radio services, including
television, telephone, telegraph, broadcasting, amateur, weather and meteorology,
navigation, research, exploration, and radio astronomy.
The 1971 conference, convened as the World Administrative Radio Conference for
Space Telecommunications (WARC-ST), and the frequency assignments it made, has been
hailed by telecommunications experts as one of the most momentous ever held in the
106-year history of the ITU because it spells out the course of extraterrestrial
communication for the remainder of this century.
The ITU is the specialized agency of the United Nations for telecommunications.
It has 140 member nations responsible for drafting the rules and regulations that
govern the allocation and use of the radio spectrum for international telecommunications.
In the more than 15 years since the Soviet Union launched Sputnik I on October
4, 1957, some 1000 spacecraft have left the surface of the earth to orbit our planet,
on journeys to interplanetary bodies, and to carry men to the moon and back. In
that, short time, space-borne scientific instruments have made and reported innumerable
observations about space and the bodies contained within it. At present, for example,
a U.S. spacecraft is hurtling toward a rendezvous with the giant planet Jupiter,
after which it will become the first man-made object to leave our solar system.
Frequencies for Communication
The following bands will now be used to transmit signals between
communication satellites and the earth (GHz =MHz X 1000):
2500−2535 MHz | 3400−4200 MHz
| 10.95−11.20 GHz
11.45−12.20 GHz | 12.50−12.75 GHz
Without frequencies with which to communicate, as well as for protection from
interference from other services, the spacecraft leaving our planet would be of
little value. Communication in one form or another plays a vital role in every satellite
departing earth. Scientific data is sent back; astronauts and cosmonauts speak to
their ground controllers, giving them essential data; photos and TV pictures of
the moon and near planets are beamed to earth via communication links; beacon transmitters
on board space-craft enable pinpoint tracking from earth stations; and even the
most minute movements of satellites can be controlled remotely from earth by means
of radio-controlled links.
An OSCAR satellite built for radio amateurs. Six such have been
Global communication has also come to rely more and more heavily on satellites.
Intelsat IV, launched early in 1972, brought to 48 the number of TV channels open
between the U.S. and other areas of the world. Communication satellites are currently
the only means by which live TV can be transmitted or received from overseas locations.
In addition, Intelsat IV can carry up to 6000 simultaneous two-way trans-oceanic
telephone conversations under average conditions. This revolution in communication
is dependent upon frequency assignments, and the 1973 Regulations make ample provision
for frequencies to be used by such services.
In addition, several bands have been allocated above 12.75 GHz for development
in the distant future.
Although broadcasting from satellites directly to home installations is not yet
technically feasible, the revised Radio Regulations allocate frequencies to the
broadcasting satellite service in anticipation of its eventual development. In the
western hemisphere, such transmissions were authorized, with certain technical limitations
(i.e., frequency-modulated video), to protect terrestrial TV stations on uhf TV
channels 39 through 66. This will permit the development of broadcasting satellites
(probably not before the end of this century) on existing TV channels so that advantage
can be taken of the large number of receivers now available in this range.
The radio amateurs came out very well under the new Radio Regulations. Always
in the forefront of communications developments, six satellites (called OSCAR's
for Orbiting Satellites Carrying Amateur Radio) designed and built by hams have
already been successfully launched. Allocations to the amateur satellite service
were made on the following frequencies:
7.0−7.1 MHz | 14.0−14.25 MHz
| 28.0−29.7 MHz
144−146 MHz | 435−438 MHz
Another broadcasting allocation was made in the 2500−2690−MHz range
to permit broadcasting to special receiving installations at schools and in community
centers, primarily for educational purposes. The U.S. and India jointly plan to
test community broadcasting from a satellite during 1974.
The new Radio Regulations also allocate 11.7-12.2 GHz (12.75 GHz in
Europe and Africa) to the broadcasting satellite service. Since there are no TV
stations operating in this range at the present time (and no receivers), this will
eventually require the development of an entirely new TV system. This is probably
the first step in the evolution of 21st century television.
Additional broadcasting allocations were made in several higher bands, but they
amount to stake-outs for development in the very distant future.
Radio Amateur Frequencies
This is a satellite earth station at Cayey, Puerto Rico. Some
70 similar stations in 50 countries link world by satellite. (Photo courtesy COMSAT).
A new satellite service was defined at the 1971 ITU conference. It was called
the earth exploration satellite service. Satellites in this service, which include
those employed for meteorological uses, will gather information relating to the
characteristics of earth and its natural phenomena. These satellites should make
possible more accurate weather forecasting and are expected to provide an accurate
cataloging of the earth's resources. Allocations in 10 discrete bands from 137MHz
to 22 GHz were assigned to this service.
There were some additional allocations made for manned and unmanned satellites
in the space research service. These are channels used to transmit telemetry data
back to earth and for beacon and tracking signals. Some 24 different bands were
allocated to this service on frequencies ranging from 2501 kHz to 8500MHz .
Still other assignments were made above 10 GHz.
Frequencies for Other Services
Anticipating that manned spacecraft will someday require assistance during an
emergency in space, the following frequencies were allocated for emergency transmissions
and for search and rescue operations in space:
2182 kHz | 3023.5 kHz
| 8364 kHz
10,003 kHz | 14,993 kHz
| 121.5 MHz
156.8 MHz | 243 MHz
A standard frequency for satellites has been established at 400.1MHz (±25
kHz), and time signals will be transmitted from satellites on two additional standard
frequencies -4202MHz and 6427MHz , ±2MHz .
The 1973 Regulations envision greater utilization of satellites for navigational
purposes and the eventual development of satellite systems that will permit aircraft
and ships to communicate via satellites. Some 13 bands have been assigned to the
navigational service for these purposes.
In addition to signals transmitted from man-made space objects, there are other
radio signals that originate deep in space. Among these are natural radio emissions
originating in the sun, the planets, and stars (and other objects such as pulsars
and quasars). To protect these extremely weak signals that reach our planet, the
Radio Regulations set aside a large number of narrow slots throughout the radio
spectrum for use in the radio astronomy service. Use of the frequencies set aside
for this service is prohibited from spacecraft, and restricted use by terrestrial
stations has been incorporated into the Regulations. Beginning in 1973, radio astronomers
will be assured that signals heard in the bands set aside for their use are not
The 1973 Regulations that are an out-growth of the 1971 conference represent
a milestone in the history of telecommunications. Assignments made by the conferees
will be used for the remainder of this century.
Posted February 21, 2020