iRKr.a('[..tRiiir.s ix i.o.idi-d rr.i.r.ftioxr. c/za r/r.v 577 



r.uh <le|x»n(ls plotted from equations (41). (1')) ;mi<I (Hi). Ilu-se 

 are all positive except as indicated !)%■ the winil "Subir.ui" oti ilic 

 diagrams. 



A simple method for cxlcndiiii; ilie cnrNe of i'ii;. "> is as follows: 

 (a) ch(H>se a point on the curve within 3 TV of the lower end, (I)) 

 subtract alxtut '.i TU (accurately, 10 logio 2) from the value of .S'/.- . 

 for this |H)int, and (c) square the value of F for this point. Tlic 

 results obtained for (b) and (c) are the coorflinates of another |)oiiii 

 on the extension of the cur\'c. 



Fig. 6 gives the relation between .S',i .iiul the transmission loss jier 

 loading section. On account of the wide use of (),000 ft. spacing the 

 curves of Fig. 7 are plotted to give the relation between Sa and the 

 transmission loss per mile for (l.OOO fi. spacing which is usualK- a 

 more conxenient arrangemeni. 



P"ig. 8 gives the amount, S„ — .S, 1)\- which the return loss of a 

 regularly terminated line of finite length (w sections) is greater than 

 that of an infinite line as a function of the transmission loss of the 

 finite line. This was calculated by formula (oO). 



C.\Lcui..\TioN <)!•• Return Loss 



The process of finding the return loss by means of the curves is as 

 follows: 



(1) Determine the value of IIl. the representative deviation of the 

 loading coils, and lie, the representative deviation of the capacity 

 of the loading sections. These depend upon the variations allowed 

 in the specifications for loading coils and cable and upon the care 

 with which the line is built. Calculate n=\/Hi+IIi:, the repre- 

 sentative combined deviation of the section. Look up the number 

 i>f TV corresponding to // in any suitable table or chart, such as 

 l"ig. 3, to find Sh. 



(2) Assume the frequency, /, to be considered. Calculate w= ^ 

 and look up the corresponding value of Sw on Fig. 4. 



(3) Assume a \-alue of F and look up the corresponding value of 

 Sp on Fig. 5. 



(4) Look up the \alue of Sa on Fig. 7, corresponding to the trans- 

 mission loss per mile of the circuit at the frequency / if the coils are 

 spaced (5,000 feet (L13G miles) apart, or calculate the loss per section 

 and look up Sa on Fig. 6, if some other spacing is used. 



(5) Calculate .S = 5//-f5„+5F-54. 



