PREFACE 



In this series of three volumes, which is part of the 

 Summary Technical Report of NDRC, the Com- 

 mittee on Propagation is presenting a record of its 

 activities and technical developments. The material 

 presented, concerning as it does the propagation of 

 radio waves through the troposphere, is of permanent 

 value both in war and in peace. 



The present volume is divided into four parts. 

 Part I outlines the organization and activities of the 

 NDRC Committee on Propagation, gives the mecha- 

 nism used for coordinating the various Service and 

 civilian organizations interested in propagation, and 

 makes recommendations for continued activity in 

 studying propagation phenomena. 



Part II gives a critical overall view of the technical 

 developments in the study of tropospheric propaga- 

 tion. Outlined is the general theory of both standard 

 and nonstandard propagation together with descrip- 

 tions and results of transmission experiments carried 

 out in widely separated parts of the earth and de- 

 signed to test the theory. Included also is a resume 

 of the meteorological factors affecting propagation 

 of waves and their attenuation in the atmosphere. 



The second, third, and fourth Conferences on 

 Propagation, under the auspices of the NDRC Com- 

 mittee on Propagation, were held in February 1944, 



November 1944, and May 1945, respectively. The 

 bulk of the technical material presented at the con- 

 ferences is published in Volume 2 of this series and in 

 Part III and Part IV of the present volume. These 

 comprise the material dealing with the theory of both 

 standard and nonstandard propagation. Certain re- 

 ports have been omitted, primarily because the 

 material was superseded by later studies or is covered 

 adequately elsewhere. 



The General Bibliography lists reports on tropo- 

 spheric propagation issued by numerous Service and 

 civilian organizations of both the United States and 

 the British Empire. With a few exceptions, original 

 reports listed in the Bibliography for this volume 

 have been microfilmed. A few, such as summary 

 reports issued by the Columbia University Wave 

 Propagation Group and the compiled Propagation 

 Conference Reports, are included in the present series. 



Acknowledgment is due to the many authors who 

 have contributed to this series, not only for the 

 material and its oral presentation at the conferences, 

 but also for their willingness to prepare the material 

 in form for permanent record. 



Stephen S. Attwood 

 Editor 



