316 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1962 



velocity to measure the difference in length of two propagation paths. 

 Various experimenters in radio, including Breit and Tuve of the Car- 

 negie Institution, working with ionosphere measurements, engineers 

 of the British Post Office working with short-wave radio, and engi- 

 neers of the Bell Telephone Laboratories working with television, had 

 observed that aircraft flying near their receivers or transmitters cre- 

 ated noticeable disturbances in the radio propagation field. This was 

 regarded merely as interference with their experiments, and otherwise 

 ignored. These constitute the elements of scientific knowledge basic 

 to the idea of radar. Since radar was not in any way an objective in 

 the discovery of these facts, since no problem was recognized for which 

 radar was the proposed solution, and since radar was only one of many 

 technological innovations dependent on these same scientific discover- 

 ies, it is not proper to ascribe to any of the named discoverers any 

 responsibility for the origin of radar by virtue of their discoveries. 



Our next step is to identify the contemporary teclinology out of 

 which radar grew. A catalogue of the state of the art in radio en- 

 gineering in the 1930's would be both tedious and superfluous. 

 Certain elements have a degree of specificity to radar, however, and 

 require special mention. The cathode-ray tube, devised by the German 

 scientist Braun in 1897 and used on an experimental basis in the early 

 1920's, became generally available as a laboratory tool in the early 

 1930's. In 1900 Nikola Tesla suggested the use of electromagnetic 

 waves to determine relative position, speed, and course of a moving 

 object. In 1903 Huelsmeyer applied for a patent in Germany on an 

 anti-collision device for ships, based on directive transmission and re- 

 ception of continuous waves at very short radio wavelengths. Trans- 

 mitter and receiver were shown on the same ship, but separated as 

 widely as possible. In Jmie 1922 Marconi again suggested the use of 

 radio as an anti-collision device. In 1923 Loewy filed a patent ap- 

 plication in the U. S. Patent Office for a radio object detector employ- 

 ing the Fizeau principle. The transmission consisted of chopped CW, 

 with approximately equal intervals on and off. A target would be 

 detected when its reflection coincided with the intervals between 

 transmission. While Loewy's disclosure appears at first to anticipate 

 radar, it fails to meet the requirements for radar, since range in- 

 dication is ambiguous, and the presence of one target would jam the 

 system for all other targets. Thus it gave no operational advantage 

 over Huelsmeyer, except the possibility of locating transmitter and 

 receiver close together. In 1925 Breit and Tuve proposed a radio 

 pulse method, which they credited originally to Swann and Frayne 

 of the University of Minnesota, for probing the ionosphere. In co- 

 operation with Taylor, Young, and Gebhard of the Naval Kesearch 

 Laboratory the method was used for the first time in that same year. 

 Although this has been said to demonstrate the basic principles of 



