250 BELL SYSTEM TECHNICAL JOURNAL 



Simultaneously with the development of this transmitting apparatus, 

 the art of measuring the strength of received radio signals and the 

 amount of static, or radio noise, present at a receiving station had 

 been developed.^ Therefore in order to try out the effectiveness of 

 the transmitting apparatus, engineers provided with suitable measuring 

 equipment were dispatched to England and set up their apparatus 

 near London. Satisfactory signals were received from the Rocky 

 Point transmitter and in January 1923, it was possible to demonstrate 

 one-way talking across the Atlantic Ocean on a much more satisfactory 

 basis than had previously been possible. 



Then there ensued a program of weekly tests wherein signals were 

 sent from Rocky Point each hour for the 24 hours of one day each 

 week and measurements of received signals, radio noise, and intelligi- 

 bility tests of spoken words were made in England. This one-way 

 telephone circuit was in other words used as a sample whereby the 

 variations to which radio telephony is subject could be explored, 

 catalogued and studied over an extended period of time so estimates 

 could be made of the improvements which would be necessary before 

 anything in the way of reliable communication could be established. 



The British General Post Office became so interested in the subject 

 as the result of the initial experiments that they decided to cooperate 

 with the American Company to the fullest extent in determining what 

 the possibilities of transatlantic radio telephony were. They therefore 

 constructed an experimental receiving station and made arrangements 

 to have a transmitter similar in general character to that being used 

 at Rocky Point installed in the new high-powered telegraph station 

 then under construction at Rugby. ^ 



The study of transmission initiated in 1923 has been continued to 

 the present time and a large volume of statistical information has 

 been collected.'^ There are two main kinds of variation which have to 

 be contended with. First, the strength of signal changes radically 



* "Radio Transmission Measurements," Ralph Bown, C. R. Englund and H. T. 

 Friis: Proceedings of the Institute of Radio Engineers, Vol. 11, No. 2, April 1923, pp. 

 115-152. 



""The Rugby Radio Station of the British Post Office," E. H. Shaughnessy: 

 Journal of the Institution of Electrical Engineers, Vol. 64, June 1926, pp. 683-713. 

 Also "Transatlantic Radio Telephony. Radio Station of the British Post Office at 

 Rugby," E. M. Deloraine: Electrical Communication, Vol. 5, July 1926, pp. 3-21. 



'"Transatlantic Radio Telephony," H. D. Arnold and Lloyd Espenschied: 

 Bell System Technical Journal, Vol. II, No. 4, pp. 116-144, or Journal of the 

 American Institute of Electrical Engineers, August 1923. Also "Transatlantic Radio 

 Telephone Transmission," Lloyd Espenschied, C. N. Anderson and Austin Bailey: 

 Bell System Technical Journal, Vol. IV, No. 3, pp. 459-507, or Proceedings of 

 the Institute of Radio Engineers, Vol. 14, No. 1, February 1926, pp. 7-56. 



