FLEXIBLE REPEATER DESIGN 



73 



(1) e^ — the gain of the Input Network 



(2) e- — the gain of the Output Network 



(3) Zc — the cable impedance 



(4) Z^ ■ — the feedback impedance 



(5) (m/S/I - /i|8) — the M^ effect term 



It should be noted that a number of simplifj'ing assumptions have 

 been made. For example, the effect of grid plate capacitance has been 

 neglected. In addition the /3 circuit has been assumed to be a two termi- 

 nal impedance whereas it is actually a four terminal network. However, 

 in the pass band and over a large part of the outband of the repeater 

 these simplifications give a very good approximation to the true gain 

 of the repeater. 



In the pass band (n^/1 — ju/3) is very nearly unity so that the gain con- 

 trolhng factors are e\ e^, and 1/Z^ assuming that Zc is fixed. 



Coupling Networks 



The input and output networks are essentially identical. The net- 

 works are of unterminated design and therefore do not present a good 

 termination to the cable at all frequencies which results in some ripple 

 in the system transmission characteristic at the lower edge of the band 

 and makes the repeater insertion gain sensitive to variations in the cable 

 impedance. However, this arrangement has the advantage of maximum 



V = OPEN CIRCUIT VOLTAGE OF INPUT COUPLING NETWORK 

 WITH El, AS THE SOURCE 



©, = GAIN OF INPUT COUPLING NETWORK DEFINED AS 6*' = V/Ej, 

 ©2= GAIN OF OUTPUT COUPLING NETWORK DEFINED AS 6*2 = L/I, 



Z,Z2= INTERSTAGE IMPEDANCES 



gf^-p = PRODUCT OF g^ OF THREE AMPLIFIER TUBES 



Fig. 3 — Simplified amplifier circuit. 



