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NAEB NEWS LETTER.._Jan. I, 1940.page 2 program of experimentation directly related to the existing station About 20 applications are ending action by the Commission for new stations desiring to use frequency modulation* There are now 34 amplitude modulated stations and 20 frequency modulated stations authorized by the Commission. Before a permanent policy can be established with respect to either or both systems of modulation on frequencies above 25,000 kilocycles for regular broadcasting service, studies and investigations must be made regarding the relative values of the two systems, the patent situation, the frequency needs of ell radio services, and whether amplitude or frequency modulation, or both systems, should be recog¬ nized for other services as well as broadcasting. It is also nec¬ essary to consider the possible future effect that broadcasting on ultra high frequencies may ultimately have upon standard broadcasting in the bend 550 to 1600 kilocycles. The frequency bands above ooroximately 25,000 kilocycles are some times referred to as -very high frequencies' 1 -, "ultra high frequencies", or "ultra short waves". These frequencies possess relatively short distance characteristics as compared with the loxver frequency bands,, The signals are subject to rather wide diurnal and seasonal variations in signal strength at distances beyond the horizon; therefore, as a practical matter, these frequencies may be said to be useful for broadcast service up to about IOC miles only* Major E. H. Armstrong, professor of electrical engineering at Columbia University, appeared as a -witness in behalf of frequency modulation at the Federal Communeations Commission engineering hearing in June, 1936. On the basis of testimony of experts who testified at this hearing, and after studies had been made Jointly by the Commission’s Engineering Eepartment and the Interdepartment Radio Advisory Committee, the Commission and the President adopted permanent allocations above 25,000 kilocycles for the various govern¬ ment and non-government radio services* Amplitude modulation h p been used as the standard system for transmitting speech . ho by radio. It is the only system of modulation which ie n-,e& by the existing services operating on conventional freqi • a ■. . i.e,, below 25,000 kilocycles. The claimed chief advantages of the two methods are set forth briefly as follows: Ampl1tude Modulation 1. Amplitude modulation utilizes a much narrower band of fre¬ quencies, i.e,, about one-f fth of the frenuenoy bend required for