55 STAT.] NORTH AMERICAN-REGIONAL BROADCASTING-DEC. 13, 1937 The tables are based upon the use of nondirectional antennas but, in case a directional antenna is employed at a particular station, it will be necessary to consider the radiation distribution of the directional antenna involved and to modify the mileage separation accordingly. The night separation tables for stations on the same frequency are computed from the skywave curve given in Appendix Pot, P. 1027. V. These curves are based on extensive measurements of the sky- wave produced by broadcasting stations and shall be considered as accurate in all cases unless proof to the contrary is available as set out in Section E 4. The mileage separation tables for the same channel during daytime and for adjacent channels day and night are computed from the groundwave curve in Appendix IV. Tables Pot, P.10'. apply only in case the frequency is 1000 kc and the assumed soil conductivity and dielectric constant prevail. Since these values vary in every case the tables for daytime and adjacent channel separation cannot be used except as a general guide. In any case under con- sideration an estimate of the mileage separation required may be made from the operating frequency and known or assumed soil conditions. To determine the interference accurately, measurements must be made in accordance with Section E 4 on the frequency under consideration or on another frequency and trom the curves the values may be determined for the desired frequency. F. MISCELLANEOUS 1. Engineering standards. The engineering standards set forth in this Agreement are subject to revision when justified by technical advances in the art, with the mutual consent of the governments parties to this Agreement. III NOTIFICATION AND EFFECT THEREOF 1. Initial notification. Each Government shall, as soon as possible after ratification of this Agreement, and in any event not later than 180 days prior to the effective date thereof, transmit to the other Governments (a) A complete list of all broadcast stations actually in opera- tion in its country in the standard broadcast band both as of the date of the signing of this Agreement and as of the date of transmitting said list, showing with respect to each station its call signal, location, frequency, power, and antenna characteristics, together with all changes authorized to be made with respect to said stations on or before the effective date of this Agreement, and the classification claimed for each such station. (b) A complete list of all changes authorized to be made with respect to said stations after the effective date of this Agreement, the dates on or before which such changes are to be consummated, and the classification claimed for each such station under this Agreement when the proposed change has been consummated. 1015
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