WAVEGUIDE AS A COMMUNICATION MEDIUM 



1249 



1.0 

 0.8 



0.2 



BEND RADIUS IN FEET 



Fig. 25 — Computed ch;uige in the 50,000 mc TKoi attenuation coefficient due 

 to bends in 1" and 2" diameter solid pipes and in modified guides having TMn 

 attenuation coefficients larger (than in solid pijic) by a factor of 100. ub and a, are 

 the bend-region and straight-line attenuation coefhcients, respectively. 



as a function of bending radius in Fig. 25, assuming the TjMh-TEoi 

 coupling due to the bend is the same in the altered guide as in solid 

 round pipe. Whereas a bending radius of 17,500 feet causes a 100 per 

 cent increase in TEoi heat loss for 50,000 mc waves in 2" diameter solid 

 pipe, the modified structure with a TMn attenuation coefficient that is 

 larger by a factor of 100 should tolerate a bending radius of 1,750 feet 

 for the same heat loss increase. (The 50,000 mc attenuation coefficients 

 for ideal 1" and 2" copper pipes are 14.8 and 1.79 db^ mile respectively.) 

 For estimating purposes, the ratio of the extra loss per unit fine length 

 in the bend region to the straight line loss ma.y be calculated for solid 

 round pipes from the relation 



as — ccs 



2.5 X 10'"a' 



(11) 



and the ab.solute increase in attcnuntion due to a IkmuI is* 



, 9.7 X lOV ru/^f ■ 1 ^ 



(as - as) = — ^ „,,p, (db/meter for copper giude) 



(12) 



* For small bend radii and bend angles less than 0c , this relation gives a greater 

 loss than the correct value. See Figs. 22 and 23 of Reference 8 and also see Refer- 

 ence 2. 



