IR.-INSMISSION Cll.iRACTERISTICS OV W.U'r.l-ILinRS 571 



iiu-an resist.inro, R, of the line with which the network is to Ik- asjio- 

 (■i.it»"<l. If the network is closed at each em! by a resistance of mag- 

 nitude R, as in Kijj. 2, we have not only a circuit arrangement whirFi 

 approximates more or less closely actual operatint; conditions,-' Imi 

 also a simple test circuit in which to determine the transmission loss 

 of the network over the desired fretiuency ranj^e. 



The transmission loss of a wave-filter network, defined with reference 

 to A7i;. 2, is the natural logarithm, with ne»ative si,ij«. of the ratio of the 

 absolute value of the current transmitted from a source of resistance R 

 to a receiving resistance R 'when the latter are connected through the net- 

 work, to that transmitted luhen they are connected directly. Let E rep- 

 resent the electromotive force of the source, / the current trans- 

 mittetl to R through the network, and E'2R that transmitted 1)\- 

 direct connection. Then the transmission loss L, thus detineil, is 



^=-'"g'i-p7opl- (1) 



ind 



(2) 



The unit in which L is expressed, the attenuation unit,''' is the natural 

 unit to use here and from the above relations it is seen that one at- 

 tenuation unit of transmission loss corresponds to an absolute value 

 of current ratio of I e. The method of determining the transmission 

 loss under various possible conditions will be presented in the next 

 part of this paper. 



11. TiiicoRV OF Chart C.mxul.xtion Method 



The principles gi\eH here are biisic and apply to composite wave- 

 filters ha\ing any terminations. However, in all practical ca.ses, as 

 pre\iously stated, the terminations belong to the four types: 1, mid- 

 shunt .U-type; 2, mid-series .U-type; 3, .v-shunt "constant k;" and 

 4, .v-series "constant k," all related to the "constant k" wave-filter. 



' It should be clearly lx>rne in niind that the unique selective properties of a 

 wave-filter of freely transmitting currents in continuous frequency bands and of 

 attenuating others arc those for the wave-filter terminated in its characteristic 

 impc<lance. It is practical to have approximately such a termination in the trans- 

 mitting band only, as when connecting the wave-filter to a transmission line, in 

 which case the general properties still persist. Correct termination rather than 

 number of sections is what brings out these properties although the degree of selec- 

 tivity is naturally increased by the addition of sections. 



• .A svnonym sometimes uscfl is the Sa(>ier. One attenuation unit is equivalent 

 to 9.174 "SOO-cycle miles of standard cable," and to 8.686 TU. The TL (trans- 

 mission unit I is that unit which designates a power ratio of 10 ', and the numtjcr of 

 TU is ten times the common logarithm of the power ratio. 



