The paper divides naturally into three sections. The first section briefly analyses the radio transmission circuit into (a) the sending or radiating portion, (b) the transmitting portion consisting of the ether path thru which the radiated waves travel, and (c) the receiving portion. The relation of these from the standpoint of the radio transmission engineer is discussed, pointing out the need of quantitative data as to electric field strengths of waves and of radio noise conditions to allow of rational design of radio systems. The second section is devoted to descriptions of apparatus which has been developed for measuring electric field strengths of radio waves, its theory and method of use. Illustrative data are given showing useful practical results already obtained at both short and long wave lengths. The third section deals with the measurement of radio noise. A useful method is described and is illustrated by examples of data from recent transatlantic telephone tests.