1114 
MONITORING 
is a condition for oscillation, that the reflection 
coefficient of the active circuit be greater than 
1. 
In practice the way to accomplish this at a 
single frequency is: (1) combine the active 
circuit and the ship antenna into a 1-port net- 
work, the active network of Figure 11 (notice 
that a matching network has been used) ; (2) 
adjust the coils, Li and L2, of the active circuit 
until Sa > 1 ; (3) terminate with a passive net- 
work that has a reflection coefficient of Sp = 
1/Sa. 
The active and passive circuits are functions 
of frequency and must be handled accordingly. 
Where the circuits are functions of frequency, 
the design procedure is to plot the reciprocal 
of the active circuit's reflection coefficient on 
the Smith chart. This plot is called the active 
circuit contour. If the active circuit is termi- 
nated with those passive impedances as read 
from the Smith chart along the active circuit 
contour then the conditions for oscillation will 
be satisfied. Furthermore, oscillations will oc- 
cur at the frequency read from the active circuit 
contour. 
If a termination other than one exactly on 
the active circuit contour is used, the circuit 
will do one of two things : (1) oscillate and over- 
drive or (2) fail to oscillate. Basically, the active 
r--i 
I I 
PASSIVE 
NETWORK 
FlQUKS 11. — Transmitter circuit. 
