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BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...
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June/July 1940 National Radio News[Table of Contents] These articles are scanned and OCRed from old editions of the National Radio News magazine. Here is a list of the National Radio News articles I have already posted. All copyrights are hereby acknowledged.
National Radio News was published bi-monthly by the folks at the National Radio Institute (NRI). NRI used to be a major training center for electronics technicians beginning in the early part of the 20th century. This article was provided for them by the Federal Communications Commission (FCC) as a synopsis of radio frequency spectrum allocations at the time. Compare a 1940 spectrum allocation chart (just a simple description here) to one for 2014 and you will see a remarkable difference in not just the number of bands, but in the extension of the frequency range. This link produces the FCC Online Table of Frequency Allocations (April 4, 2014) document, and this one is a more user-friendly equivalent graphical chart recently published by Wireless Design & Development magazine.
BBTW, the picture below has nothing to do with the article. It appeared on the table of contents page and I thought it would make a good addition since the article itself had no image.
This article was released to National Radio News by the Federal Communications Commission, Washington, D. C.
The radio spectrum, or radio waves form one portion of the total electromagnetic spectrum. The electromagnetic spectrum covers eight different classes of radiation-electric waves, radio waves, infra-red, visible light, ultra-violet, X-rays, gamma rays, and secondary cosmic rays.
The emission of this energy may be likened to the expanding ripples of water suddenly disturbed by a thrown stone. However, electromagnetic energy travels in all directions.
Since electromagnetic radiations have a common speed (that of light), their only difference is in frequency and wave length. "Frequency" may be characterized as the number of these waves per second, and "wave length" as the distance between successive waves.
The divisions between the various classes of electromagnetic radiations are not definite. The lines of separation are based largely upon the effects and the particular method of producing the various emissions. Under certain conditions, some of these electromagnetic impulses may be seen, felt, or heard. Of the eight classes of electromagnetic radiations, that portion classed as "radio waves" covers a relatively small part of the total electromagnetic spectrum.
Radio facilities are extremely limited. In order to provide the maximum possible service for the benefit of the public, it is necessary to control and restrict the use of the available channels. As transmission by radio waves spans great distances, it has been found necessary to have international agreement on the proportion of available channels to be allocated for particular services. To prevent interference within our own country, it is necessary to further apportion the frequencies in the best interests of users.
Besides the standard broadcast channels. our radio spectrum is shared by other primary services, such as: fixed, marine, aviation, emergency, amateur, miscellaneous, experimental, Government, and broadcast services other than standard broadcast. These general service allocations cover various classes of station, including: relay, international broadcast, high frequency broadcast, noncommercial education, facsimile, television, point-to-point telephone and telegraph, agriculture, press, coastal, telegraph and telephone, ship, aircraft, aeronautical, blind landing systems, airport, municipal and State police, marine fire, forestry, geological, mobile press, motion picture, amateur phone, telegraph and television, as well as experimental classes of stations.
The present useful radio spectrum, in which channels are now allocated, ranges from 10 to 300,000 kilocycles, or in terms of wave lengths from 30,000 meters to 1 meter. That portion below 100 kilocycles is popularly referred to as "long waves"; from 100 kilocycles to 550 kilocycles as "medium long waves'"; from 550 to 1600 kilocycles as "broadcast" ; 1600 to 6000 kilocycles as "medium short waves"; 6,000 to 30,000 kilocycles as "short waves"; and above 30,000 kilocycles as "very short" or "ultra-short waves."
The band below 100 kilocycles is occupied by Government and commercial long wave fixed service stations. From 100 kilocycles to the beginning of the broadcast band at 550 kilocycles we have the medium long wave stations, as follows: 100 to 200 kilocycles - Government and private ship, coastal, and fixed service stations.
200 to 400 kilocycles - primarily Government aids to navigation, such as radio navigation for aircraft, and radio beacon service to ships, interspersed with airport on 278 kilocycles, direction finding on 375 kilocycles, and miscellaneous fixed stations.
400 to 550 kilocycles - Government and commercial ship and coast stations in the maritime service centered near the international calling and distress frequency of 500 kilocycles (600 meters).
The rest of the spectrum from the end of the "broadcast" band at 1600 kilocycles, involving the so-called "medium short," "short," and "ultra-short" wave bands, could be pictured as a many layered sandwich, with police, amateur, aviation. Government, ship, coastal, broadcast, mobile press, special services, experimental television fixed, forestry, and all other classes of stations providing varying depths of filling.
Of course, this does not mean that all these bands are completely filled. Radio communications is still undergoing change, and the Federal Communications Commission, in licensing individuals and firms to use the public's radioways, is charged with preparing for the future, as well as for the present. Hence, some channels are held open for future developments, while others already allocated, are subject to shift with changing events.
Posted APril 8, 2014