1246 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1954 



3.24 3.28 3.32 3.36 3.40 3.44 

 WAVELENGTH, \o» 'N CENTIMETERS 



3.48 3.52 3.56 



Fig. 24 - 

 TE21 , TM, 



Observed conversion from TEni to TEu , TE21 , and the sum of TEa , 

 , TMoi , and TE31 for the 500-foot line. 



Aronoff at 9000 mc on accurately created imperfections of the above 

 types, and he found excellent agreement. We proceed to use the theory 

 to compare the present line to a hypothetical 50,000 mc line. The re- 

 sults are given in Table II. 



These computations represent a single oval section or a single tilted 

 or offset joint. The converted power varies as the scjuare of the tilt angle, 

 as the sciuare of the offset distance, and as the square of the difference 

 between the major and minor diameters. The total ratio of converted 

 power to heat loss power depends on the number of conversions per unit 

 length. For the accuracy of constructing a 2" diameter line assumed in 

 Table II, the amount of mode conversion to be expected is not appre- 

 ciably different from what appears attributable to known mechanical 

 imperfections in the 500-foot line already discussed. 



Another waveguide property of interest is the way the mode conver- 

 sion magnitudes vary across the frecjuency band in a fixed pipe, and 

 Table III shows this for the 2" diameter line. 



