1500 INTERNATIONAL AGREEMENTS OTHER THAN TREATIES [55 STAT. c) Permissible values of interfering signal strength for the various types of radio aids to air navigation expressed in ratios of desired to undesired signal measured at the minimum signal contour (a) on the same frequency, and (b) on frequencies removed therefrom by specified numbers of kilocycles. 2.- that radio aids to air navigation, especially those which are of a one-way or broadcast nature, such as radiobeacons, should maintain the highest possible standards of reliability, stability and quality of emissions. 3.- as far as possible, all nations should reserve the same wave bands for similar types of service in order to simplify radio equipment design and through such standardization extend the geographi- cal limits of usefulness of aircraft radio equipment. 4.- that the power radiated by radio aids to air navigation in the authorized frequencies bands should be consistent with the normal required signal intensity within the area in which it is desired to render service. XVII AIR NAVIGATIONAL AIDS. It is recommended: that inasmuch as the next world aeronautical radio conference will probably consider the standardization on a world-wide basis of reduced visibility radio landing devices for aircraft, information be exchanged between the governments which have conducted experimentation on devices of this nature, and also between other governments signatory to this agree- ment. EXPLANATORY NOTE The resolutions and new questions dealing with aeronautical communications are the result of discussions which used as a basis some of the recommendations drafted by the Subcommission of the Third World Conference of Aeronautical Radio Experts which met at Krakow, Poland, in May 1939. XVIII AMATEURS (GENERAL). It is recommended: a) Require amateurs operating radiotelephonic services in the band 14000 to 14400 kc to go through a period of preliminary training assuring a minimum of experience in order to insure the efficient use of this band. b) Prohibit the employment of amateur stations, both fixed and mobile, from rendering a broadcasting service, and make every effort to limit operations to specific purposes, without invading the sphere of activity that properly belongs to other radio services.
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