TR.I.\S.II I^IMIC K.iniO ll-lJil'llOXi: IK.IWMISSIOX 4<0 



(given in tht- chart of Fin. \) lit- in a ranKf in-lwrrn lo and <)() kr. 

 The arrows indicate the single fre(iiiency tr.insniissions whicii were 

 emplo>ed for signal field strength measurements, those at the left 

 indicating the fret|Uencies received in the United Stales from I'.ngiand, 

 and those at the right, the frecjuencies received in fuigl.ind from the 

 I'nited States. The l)lack scjuares in the chart denote ttie hands in 

 which the noise me.isurements were l.ikcii. In i;iiici-,d llic measure- 



Fig. 4 — Frequency di.stribution of measurements. Black squares tleridte t>and in 

 whiih noise measurement was taken 



nients of both fickl strength and noise have been carried out on both 

 sides of the Atlantic at hourly intervals for one day of each week. 

 The data presented herewith are assembled from some 40,000 in- 

 dividual measurements taken during the past two years in tlic fre- 

 (|uency range noted above. The transmitting antenna current has 

 l)een obtained for each individual field strength measurement and all 

 values corrected to a definite reference antenna current for each 

 station measured. The data have been subject to careful analysis 

 in order to disclose what physical factors, such as sunlight and the 

 earth's magnetic field, affect radio transmission. 



Measurement Methods 

 Although it will not be necessary to describe in atu detail tlie t\pc of 

 apparatus employed in making these measurements, as this informa- 

 tion has already been published,' a brief review of the methods involved 

 will facilitate an unflerstanding of the data. 



' RaHio Transmission Measurements, Bown, Engiund, and Friis. Proceedings 

 I R K., April, 1923. 



