TRANSATLANTIC RADIO TELEPHONY 317 



of hourly measurements of the field strength made at Houlton and 

 Wroughton during the time that the transatlantic path was entirely 

 in daylight during 1927 is indicated by points on this figure. The 

 data for Cupar are less complete since this station was not in regular 

 daily operation until May, 1927. The range of variation between the 

 maximum daily average and the minimum daily average for each 

 receiving location is given by the limits of the dotted vertical line. 

 (It is interesting to note that at a frequency of 60 kilocycles and for 

 distances in the order of 5,000 kilometers any of the radio-transmission 

 formulas referred to above will give a computed value lying within the 

 range of variation of average daylight readings.) 



The improvement in signal-to-noise ratio obtained by locating the 

 receiving station in Maine instead of in New York is easily seen by 

 reference to Figs. 3 and 4. The improvement due to decrease of 

 noise, during that time of year when improvements are most needed 

 on account of high noise values, is about 10 TU. The improvement 

 due to increase of the average received daylight signal by decrease of 

 the distance is calculated to be 5 TU. During 1927, this improve- 

 ment was actually observed to be 8 TU. We may, therefore, state in 

 round numbers that the total improvement realized by locating the 

 receiving station in Maine instead of New York was equivalent to a 

 fifty-fold increase of the power radiated by the British transmitting 

 station. 



The British General Post Office, during 1926, carried out a set of 

 measurements of field and noise at various locations in the United 

 Kingdom. Those tests led them to the same conclusions as regards 

 the advantage to be obtained by locating their receiving station at 

 some more northerly point. ^^ They decided upon a location near 

 Cupar, Scotland, and comparisons made daily from 1230 to 2300 

 GMT indicate that this location is better for receiving than Wrough- 

 ton, England. The geometric mean of the improvement in signal-to- 

 noise ratio for the more northerly location during the months May to 

 September, 1927, inclusive, and for the daily period given above is 

 6.4 TU. This is equivalent to an increase of between four and five 

 times in power from the American transmitting station. 



Since such relatively large improvements were to be obtained by 

 northerly locations of the receiving station it seemed best to take 

 advantage of this fact and locate the receiving station in America at 

 some place in the state of Maine. This decision led to further con- 

 sideration of two factors mentioned above, namely, reliable wire 



1' A. G. Lee, "Wireless Section: Chairman's Address, Jour. I. E. E., 66, 12; Dec, 

 1927. 



