December 1971 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.
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, an 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 October 8, 2018