OVERSEAS RADIO EXTEXSION 263 



useful, 110 hours, or about 3 i:)er cent of the time, were lost due to 

 interference from other stations. The frecjuencies of the interfering 

 stations were found to differ from their registered frec}uencies by vary- 

 ing amounts up to hundreds of kilocycles. 



The Hague 1929 Conference of the C.C.I.R. recommended that 

 the frequencies of fixed stations operating in the 6,000 to 23,000-kc. 

 range be held to 0.05 per cent tolerance and improved to 0.01 per 

 cent as soon as possible. That this is not an unreasonable recjuire- 

 ment for large stations is indicated by the following results of meas- 

 urements made on the four short-wave telephone transmitters at 

 Lawrenceville, N. J., during the periods of regular operation for the 

 first half of 1930. Of 2826 measurements of the frequencies of these 

 transmitters which were made at a measuring bureau 99.75 per cent 

 were within the ± 0.05 per cent deviation, and 89.1 per cent were 

 within the ± 0.01 per cent. 



The existence of the problems of the transmitting medium and of 

 the reduction of interference is a reminder of the need which exists 

 for further quantitative studies of radio transmission throughout the 

 world and of radio station performance, in the interest of the more 

 effective use of the radio channels of the world. 



Bibliography 



1 Ralph Bown, "Some recent measurements of transatlantic radio transmission," 

 Proc. Nat. Acad, of Sci., 9, Xo. 7, 221-225; July, 1923. 



2. H. D. Arnold and Lloyd Espenschied, "Transatlantic radio telephony," Jour. 

 A. I. E. E., August, 1923; Bell Sys. Tech. Jour., October, 1923. 



3 H. \V. Nichols, "Transoceanic wireless telephony," Electrical Commumcation, 

 2, Xo. 1, July, 1923. 



4. A. A. Oswald and J. C. Shelleng, "Power amplifiers in transatlantic radio teleph- 

 ony," Proc. L R. E., 13, 313-363, June, 1925. 



5 R A. Heising, "Production of single side-band for transatlantic radio telephony," 

 Proc. I. R. E., 13, 291-313, June, 1925. 



6. Lloyd Espenschied, C. X. Anderson, and Austin Bailey, "Transatlantic radio- 



telephone transmission," Bell Sys. Tech. Jour., July, 1925. (Also I. R. E.) 



7. S. B. Wright and H. C. Silent, "The Xew York-London telephone circuit," 



Bell Sys. Tech. Jour., 6, 736-749, October, 1927. 



8. Frank B. Jewett, "Transatlantic telephony," Scientific Monthly, 25, 170-181, 



August, 1927. 



9. Ralph Bown, "Transatlantic radiotelephony," Bell Sys. Tech. Jour., 6, 248- 



257, April, 1927. 



10. K. \V. Waterson, "Transatlantic telephony — service and operatmg features," 



Jour. A. I. E. E., 47, 270-273, April, 1928; Bell Sys. Tech. Jour., 7, 187-194, 

 April, 1928. 



11. O. B. Blackwell, "Transatlantic telephony— the technical problem," Jour. 



A. I. E. E., 47, 369-373, May, 1928; Bell Sys. Tech. Jour., 7, pp. 168-186, 

 April, 1928. 



12. Frank B. Jewett, "Some research problems m transoceanic telephony," Proc. 



Amer. Soc.for Testing Materials, 28, Part 11, 7-22, 1928. 



13. Austin Bailey, S. \V. Uean, and W. T. Wintringham, "Receiving system_^for 



long-wave transatlantic radiotelephony," Proc. I. R. E., 16, 1645-1705, 

 December, 1928. . . „ 



14. Clifford X. Anderson, "Transatlantic radio transmission and solar activity, 



Proc. I. R. E., 16, 297-347, March, 1928. 



