Chapter 4 

 RESULTS AND RECOMMENDATIONS 



4.1 



RESULTS 



Any tabulation of the results of the Committee's 

 work must be based to a degree on certain 

 intangibles difficult to evaluate. This is because a 

 substantial proportion of the overall result was a 

 change in the attitude of agencies and personnel 

 concerned with the performance of radar and radio 

 equipment using the frequencies above about 30 mc. 

 The complete analysis and understanding of propa- 

 gation of these frequencies through the troposphere 

 still lies in the future and will undoubtedly require 

 much additional experimental and theoretical work, 

 conducted without the restrictions of wartime secrecy 

 and urgency. However, a considerable overall tangible 

 result was also achieved, both in establishing the 

 basic theory of tropospheric propagation and 

 in development of methods and instruments for 

 measuring meteorological factors influencing such 

 propagation. 



In the earlier stages of the war, nonstandard (at 

 first called "anomalous") propagation caused several 

 confusing and disconcerting incidents, due to misun- 

 derstanding of the phenomena. The instance later 

 called "The Battle of the Pips," which took place 

 near the Aleutians, was paralleled in other theaters 

 many times. In this case echoes returned from 

 islands ordinarily beyond radar range caused such 

 confusion that fire was opened and an attempt made 

 to engage nonexistent enemy units. Such puzzling 

 and exasperating variations in radar and radio 

 performance caused serious loss of confidence in 

 equipment and was of considerable operational sig- 

 nificance. This has been considered more fully in 

 Chapter 1, as it was directly related to the origin 

 of the Committee. 



The general effect of such publications as Varia- 

 tions in Radar Coverage, of which upwards of 30,000 

 copies were distributed, Tropospheric Propagation 

 and Radio Meteorology, and numerous other reports 

 prepared and distributed for the Committee by the 

 Columbia University Division of War Research 

 [CUDWR] Wave Propagation Group [WPG] under 

 contract OEMsr-1207, was to restore confidence in 

 the equipment and its use and to focus attention on 

 other causes of unreliability, which previously were 



often masked by or confused with the effects of 

 propagation variations. These other sources of vari- 

 able performance, principally misadjustment of or 

 defects in equipment caused by the rigors of field 

 service, became easier to track down and eliminate, 

 because they could be distinguished from propaga- 

 tion effects with reasonable success when the latter 

 were understood. 



Another general result of the Committee's work 

 was a considerable modification of siting principles 

 for radar and radio equipment The results of the 

 Caribbean over-water experiment, and of similar 

 tests conducted at San Diego, Cape Cod, and across 

 the Irish Sea, conclusively demonstrated the frequent 

 existence of relatively stable horizontal layers of the 

 lower atmosphere, in which the vertical distribution 

 of refractive index was such as to cause substantial 

 departures of actual radar coverage and radio com- 

 munication range from the values obtained in a 

 standard atmosphere. In particular, it was deter- 

 mined that, over much of the tropical and semi- 

 tropical areas of the oceans, such layers were prevalent 

 during many months, varying in thickness and 

 intensity with wind speed and other measurable 

 meteorological variables. These surface layers often 

 produced large increases in radar ranges on surface 

 craft and low-flying aircraft for radars of appropriate 

 frequency sited in or close above the duct. 



These investigations also revealed that under 

 certain conditions a reverse effect could occur, in 

 which the radiation was refracted downward much 

 less than in a standard well-mixed atmosphere, with 

 the result that coverage was less than normal. In 

 extreme cases the radiation might even be bent 

 upward away from the surface, resulting in ranges 

 less than optical. In the course of arriving at these 

 general results, methods and instruments for measur- 

 ing the meteorological factors producing these effects 

 were developed, particularly the Massachusetts 

 Institute of Technology [MIT] psychrograph and 

 the State College of Washington [WSC] wired sonde, 

 with techniques for interpreting the data in approxi- 

 mate terms of radar performance. These instruments 

 and techniques were made available to the armed 

 forces of the Allied Nations. 



A total of about 550 reports on various aspects of 



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