class to which the station belongs, the field intensity of an interfering station (or the root-mean -square value of the field intensities of two or more interfering stations) operating on the same channel, exceeds for ten (10) percent or more of the time the value of the permissible Post, p. 102. interfering signal set forth opposite such class in Appendix II. 4. Interference to dominant clear channel stations. A station shall be considered as not capable of causing objectionable interference to a Class I clear channel station on the same frequency when it is sepa- rated from the dominant clear channel station by a difference of 70 degrees or more of longitude. 5. Objectionable interference on adjacent channels. It is recognized, in principle, that objectionable interference may be caused to a desired station when, at or within the specified contours of a desired station, the field intensity of the ground wave of an undesired station operating on an adjacent channel (or the root-mean-square value of the field intensities of two or more such undesired stations operating on the same adjacent channel) exceeds a value determined by the following ratio: Separation Minimum permissible ratio between channels of desired to undesired signals 10 kc 1to 0.5 20 kc 1to10 30 kc 1to50 For convenient reference, the maximum permissible values of interfer- ing signals on such adjacent channels at specified contours are set forth Pt,. p.10.5 in Appendix III, Table I. 6. Application of standards to existing stations. (a) For the purpose of estimating objectionable interference, all stations (other than those of Class II) shall be assumed to use the maximum power permitted to their respective classes. In this connection, the power of Class I-A stations shall be considered to be 50 kw or the actual power, if higher. (b) After this agreement has been placed in operation a station thereafter assigned a channel already assigned to other stations shall not be considered as preventing existing stations from increasing their power to the maximum allowed their class, even though such power increase may limit the newly assigned station to a field in- tensity contour of higher value than that permitted its class. 7. Frequency stability The operating frequency of each broad- cast station shall be maintained to within 50 cycles of the assigned frequency until January 1, 1939, and thereafter the frequency of each new station or each station where a new transmitter is installed shall be maintained within 20 cycles of the assigned frequency, and after January 1, 1942, the frequency of all stations shall be maintained within 20 cycles of the assigned frequency. 8. Spurious radiation. The governments shall endeavor to reduce and, if possible, eliminate spurious radiations from broadcast stations. Such radiations shall be reduced in all cases until they are not of sufficient intensity to cause interference outside the frequency band 1012 TREATIES [55 STAT.
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