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. 
{In Volume 1, Part I] gives a critical overall view 
of the technical developments in the study of tropo- 
spheric propagation. Outlined is the general theory 
of both standard and nonstandard propagation 
together with descriptions and results of transmission 
experiments carried out in widely separated parts of 
the earth and designed to test the theory. Included) 
also is a résumé of the meteorological factors affect-) 
ing propagation of waves and their attenuation in 
the atmosphere. | 
One of the important contributions of the NDRC 
Committee on Propagation of permanent value is 
the publication of the technical papers presented at 
the several Conferences on Propagation. The first 
Conference was held at the Radiation Laboratory at 
Massachusetts Institute of Technology in July 1943 
prior to the formation of the Committee on Propaga- 
tion. Those sponsored by the Committee were the 
second, third, and fourth Conferences held, respec- 
tively, in New York, February 1944; in Washington, 
November 1944; and in Washington, May 1945. 
The bulk of the material published is taken from 
the Columbia University reports and from the papers 
presented at the third and fourth Conferences; the 
remainder comes from the second Conference. By 
careful selection it has been possible to avoid exces- 
sive repetition; and yet on continuing projects, such 
as transmission studies, it is possible to follow their 
development over a considerable period of time. 
Some of the material has been published in 
Volume 1 of this series — that dealing with the 
theoretical aspects of propagation, both standard and 
nonstandard. In [Part I of Volume 2] the subject 
considered is meteorology: first theory, then equip- 
ment, and finally the development of forecasting 
techniques in which the ultimate goal is the ability ! 
to predict radio performance from meteorological 
measurements made considerably earlier. 4 
[In Part II of Volume 2 a chapter] on reflection 
coefficients presents a certain amount of new material 
which, however, tends to confirm previous views and 
further substantiates formulas already available. 
[In a chapter] on dielectric constant, absorption, and 
scattering, the reader will find a considerable volume 
of new material. With decreasing wavelength the 
*The Editor’s Prefaces to the three volumes of the Sum- 
mary Technical Report of the Committee on Propagation 
have been consolidated and abridged for reprinting as the 
Preface to the present volume. 
absorption by the components of the atmosphere 
becomes increasingly important while the problems 
of absorption and scattering, as related to wavelength 
and water droplet size, bear importantly on the abil- 
ity to track clouds and storms by radar. 
[In a chapter] on echoes and targets, the reader 
will find an interesting treatment of some of the more 
unusual problems concerning the radar behavior of 
targets. Volume 2 closes with a consideration of an 
angle-of-arrival experiment. 
The material presented [in Volume 3] was prepared 
by the Columbia University Wave Propagation 
Group at the request of the Committee on Propaga- 
tion of the National Defense Research Committee. 
The International Radio Propagation Conference, 
meeting at Washington in May 1944, recommended 
that a book be prepared dealing with problems of 
radio wave propagation in the standard atmosphere 
at frequencies above 30 megacycles. The importance 
of these higher frequencies is apparent when it is 
recalled that most radars operate in this range and 
that an increasing number of communication circuits 
are being equipped for operation above this fre- 
quency. 
A certain amount of evidence from operational 
theaters indicates that lack of familiarity with the 
underlying theory of propagation and calculations 
based thereon not infrequently has resulted in 
ineffective installation and operation of radar and 
communication sets. This is ascribable, in part at 
least, to the lack of publications which give a clear 
picture of the problems of propagation or show how 
the important factors may be evaluated. 
A considerable volume of basic material on 
propagation had appeared in technical journals 
before World War II, and during the war a great 
quantity of classified material has come from 
laboratories and operational theaters, illustrating 
new applications of old principles, giving valuable 
information on propagation problems as well as on 
characteristics of radar and communication sets, 
antennas, targets, siting problems, etc. But this 
information has not been coordinated under one 
cover for practical use by signal personnel in the 
field. The Columbia University Wave Propagation 
Group was asked to undertake this task, and it is 
hoped that this book will, in some measure, answer 
the need. 
Our effort, then, has been to provide a hook 
designed for men with college training in radio, 
physics, or electrical engineering, which states the 
basic laws of propagation, that is, shows how the 
characteristics of the earth and the atmosphere 
control the propagation of radio waves; gives the 
fundamental properties of the basic types of antenna 
