Page:United States Statutes at Large Volume 62 Part 3.djvu/48

 62 STAT.] CANADA-RADIO BROADCASTING Dec.T24 2653 Apr. 1, 19482 5 kilocycles to 1600 kilocycles will be recognized as acceptable for use concurrently with the 10% Skywave Signal Range Curves (Figure 1-A) for determining the value of an inter- fering signal to an existing station. "(b) The antenna system's maximum theoretical radiated field which exists between the limits defined by curves 4 and 5 for the pertinent angle of departure 0 (theta) will be used to compute, from Figure 1-A, the interfering signal. "3. 50% Root-Sum-Square. "(a) Objectionable interference shall be deemed to exist to a station when the root-sum -square value of interfering field intensities, except in the case of Class IV stations on local channels, is increased to exceed that value obtained by con- sidering the signals in order of decreasing magnitude, add- ing the squares of the values and extracting the square root of the sum, excluding those signals which are less than 50% of the root-sum-square value of the higher signals already included. "(b) The root-sum-square value will not be considered to be increased when a new interfering signal is added which is less than 50% of the root-sum -square value of the inter- ference from existing stations, and which at the same time is not greater than the smallest signal included in the root- sum-square value of interference from existing stations. "(c) It is recognized that application of the above '50% ex- clusion' method of calculating root-sum -square interference may result in some cases in anomalies wherein the addition of a new interfering signal or the increase in value of an existing interfering signal will cause the exclusion of a previously included signal and may cause a decrease in the calculated root-sum -square value of interference. In such instances, the following alternate method for calculating the proposed root-sum -square values of interference will be em- ployed wherever applicable. "(d) In the cases where it is proposed to add a new inter- fering signal which is not less than 50% of the root-sum- square value of interference from existing stations or which is greater than the smallest signal already included to obtain this root-sum-square value, the root-sum-square limitation after addition of the new signal shall be calculated without excluding any signal previously included. Similarly, in cases where it is proposed to increase the value of one of the existing interfering signals which has been included in the root-sum -square value, the root-sum-square limitation after the increase shall be calculated without excluding interfer- ence from any source previously included. "(e) If the new or increased signal proposed in such cases is ultimately accepted, the root-sum-square values of inter-

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