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December 1971 Popular Electronics
 Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
from
Popular Electronics,
published October 1954 - April 1985. All copyrights are hereby acknowledged.
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The World Administrative
Radio Conference (WARC) is associated with the International Telecommunications
Union (ITU). It is hard to pin down exactly when the organization's name official
became the WARC since it is no longer a separate entity, and good luck locating a
definitive history on the WARC proper. The closest I could come to determining a
time when it was first referred to as the
World Administrative Radio Conference was from this list of all
radio conferences on the ITU website. The Geneva
1967 WARC is it. Previous events did not include the word "World"
in them, from what I could find. Please let me know if you have another authoritative
source. This
1971 WARC for Space Communications was the first to emphasize
allocation of frequencies to satellite operations. The
1979 WARC is heralded as the most significant ever as is set the
framework for what still exists today, having taken eleven weeks to complete. Thousands
of pages of
documents filled with regulations, equations, and graphs were
collected as part of the record.
A Report on the World Administrative Radio Conference
 By Richard G. Gould
Newly Proposed WARC Regulations Emphasize Satellites
The WARC is over. Representatives of 101 countries attended. The United States
sent a 50-man delegation headed by an ambassador. The WARC lasted for six weeks,
including one marathon session that ran around the clock from Saturday morning till
dawn on Sunday. WARC stands for the World Administrative Radio Conference, and was
typical of such conferences held about every eight years to revise the Radio Regulations
and the Table of Frequency Allocations.
Did we get what we wanted? Can we use the new frequencies that were allocated?
What kinds of new space services and systems are now possible?
When the Final Acts of the WARC take effect on January 1, 1973, satellites may
be used by the space counterparts of many existing services such as the Amateur,
Maritime and Aeronautical Mobile and Radionavigation, Meteorological Aids and the
Broadcasting Services. In addition, frequencies were allocated to two completely
new services: Earth Exploration and Inter-Satellite. The previous Conference allocated
frequencies up to 40 GHz. This one extended the Table to 275 GHz.
Broadcasting Satellite Service
While all the new allocations don't agree exactly with the ones the United States
had proposed, every service got frequencies in or near most of the bands we wanted.
One surprising and gratifying result was the allocations made to the Broadcasting
Satellite Service. The Conference agreed on primary allocations for space broadcasting
in the bands from 2500 to 2690 MHz, 11.7 to 12.2 GHz, 41 to 43 GHz and 84 to 86
GHz, the last two bands being exclusive and the rest shared with other services.
(A primary allocation means that a user can't cause interference to other primary
users, and they can't interfere with you. A secondary allocation means you can't
cause interference, but others can cause you interference.)
In the uhf band, space TV broadcasting will be permitted between 630 and 790
MHz (that is, on channels 40 through 67) on a "footnote basis". This means that
the service is not listed in the Table of Allocations itself, but mentioned in a
footnote. This footnote also specifies the precautions that must be taken, including
the statement that broadcasting can only take place "subject to agreement among
administrations concerned ... and affected." In other words, the other services
come first and space broadcasting cannot interfere with them. Still, it brings a
little closer the day when people may be able to dial the satellite on their TV
receiver at home. The 2500-MHz band is also attractive. Although there are no receivers
built for TV at these frequencies now, sets could be designed to sell at reasonable
prices. Among the uses seen for this band is service to remote areas of the United
States, such as Alaska, for both television and telephone to small settlements in
the bush.
The other frequencies above 10 GHz allocated to space broadcasting will be more
difficult and expensive to use because of the increased complexity of receivers
for these bands: but they have been allocated and will be available as the need
for space broadcasting develops and as we learn how to build less expensive equipment
for these bands.
Fixed Satellite Service
The Communication Satellite Service, renamed the Fixed Satellite Service, got
some new frequencies: most of them shared with other services, but some of them
exclusive. For example it will now share a portion of the 2500-MHz band with the
Broadcasting Satellite Service mentioned above, as well as with the Fixed and Mobile
Services.
Communications satellites were also added to the bands from 10.95 to 11.2 GHz,
11.45 to 11.7 GHz and 12.5 to 12.75 GHz where they must share with the Fixed and
Mobile Services, and in the band from 11.7 to 12.2 GHz which they must also share
with Broadcasting satellites.
Fixed satellites were also added to one other band below 10 GHz for down-link
transmissions, and to the band from 14.0 to 14.5 GHz for up-links. The new down
band, 6625 to 7125 MHz, is particularly desirable because rain attenuation effects
are not as severe there as they are above 10 GHz. However, it may be difficult to
use this band with the new 14-GHz band because of harmonic interference problems.
We hadn't proposed the 14-GHz band, suggesting instead a band around 13 GHz, that
is not harmonically related to the 7-GHz frequencies, but 14 GHz was the only one
all nations could agree on.
Communications satellites also got 12 more bands between 17.7 and 275 GHz. These,
of course, are subject to the high attenuation caused by precipitation and would
undoubtedly have to be used with space diversity earth stations. Space diversity,
long used on the ground to overcome the effects of fading on microwave systems,
becomes much more expensive when communicating with satellites. On the ground, antenna
separations of up to 80 feet on the same tower are adequate. Thus, one only need
add a second antenna and receiver. To combat rain attenuation in satellite systems,
entire duplicate earth stations must be built, located up to 20 miles apart, and
interconnected by microwave or cable systems on the ground.
Amateur and Other Satellites
In the case of the other existing services, satellite techniques will now be
permitted in many bands that had been assigned to those same services. For example,
all amateur bands that had been allocated exclusively on a world-wide basis, can
now be used for transmitting from amateur satellites. Actually, a group of amateurs
has been working for several years to build these satellites, to arrange for their
launch, and to work for the establishment of the Amateur Satellite Service and the
allocation of frequencies to it.
Amateurs first banded together in California during 1960 to form the Project
Oscar Association. This group was responsible for four satellites between 1961 and
1965. Amsat, the Amateur Radio Satellite Corporation, was formed in 1969 as a non-profit
corporation to continue the work of Project Oscar. To date, this new organization
has arranged for the launch of one satellite, Australis Oscar-5, a 40 pound spacecraft
built by students in Australia. Amsat is now working towards the 1972 launch of
another Oscar satellite which, according to plans, will contain three transponders.
The organization has also formally proposed to NASA to provide an amateur package
called Syncart (Synchronous Amateur Radio Transponder) on the ATS-G satellite, scheduled
for launch in 1975. Licensed amateurs and others interested in amateur radio can
learn more about Amsat, and how they can participate, by writing to P.O. Box 27,
Washington, D.C. 20044.
As another example of space techwaves being added to existing services, the band
from 1540 to 1660 MHz, long allocated to aeronautical radionavigation, has been
extended down to 1535 MHz and then split into several pieces, some of which are
still allocated only for airborne radars, but now satellites may be used to assist
in air navigation. Other pieces of this band were allocated to maritime mobile and
aeronautical mobile satellites. As a consequence, satellites may eventually supply
voice and data circuits, not only to the officers of ships and planes for necessary
communications while crossing the oceans, but for commercial telephone service to
passengers.
One of the new services, for earth exploration, was added to many bands. It is
now a secondary service in the band from 1525 to 1535 MHz, a primary service sharing
with other users in the bands from 8025 to 8400 MHz and 21.2 to 22 GHz, as well
as in two bands above 51 GHz, and lastly, on a footnote basis in three more UHF
bands. In the future, these satellites will both receive transmissions of data from
remote, unmanned sensing stations around the world, and take pictures of the earth,
sending all their output to centrally located stations for processing and analysis.
Among the satellites that have already been put to these purposes are the Tiros
and Nimbus.
The other new service was established to provide for relaying of signals between
satellites. Called the Inter-Satellite Service, it was given several allocations
between 54.25 and 190 GHz. These frequencies are difficult to use for space-to-earth
links because of the high attenuation due to precipitation and to absorption phenomena
in the atmosphere, but they are well suited to transmissions wholly outside the
earth's atmosphere.
Although the Final Acts of the WARC will be in force internationally in 1973,
they must be ratified by the President with the advice and consent of the Senate,
before we will be bound by them. Assuming that this ratification takes place without
a hitch, the FCC will then be able to revise its rules so that domestic users can
take advantage of these new frequencies.
Posted May 28, 2024
(updated from original post
on 10/8/2018)
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