potential until C86; becomes charged. Capacitor C86
R80, R81, R82, and RT1. When S1 is in the X5 position,
charges slowly through R113 to the positive voltage
the audio voltage is applied to the modulator input
present across R102. The long time constant of the
through a constant impedance attenuator consisting of
series combination produces a time delay of several
R9, R10, R121, and R8. When S1 is in the X1 position,
seconds before the voltage across C86 reaches a value
the audio voltage is applied to the modulator input
that raises the grid potential of V16 above the cutoff
through a constant impedance attenuator consisting of
value. When V16 conducts, its plate voltage drops; this
R11, R13, and R14.
results in a decrease in the positive potential across
R117. A decrease in the positive grid voltage reduces
51. Surge Circuit V16 and V17
current flow through V17 and causes its plate voltage to
a. The surge circuit (fig. 17) is a one-kick dela
y
rise. At the same time, positive bias potential across
R118 is reduced, current flow through V16 is increased,
supply is energized. Its purpose is to develop a pulse of
and its plate voltage again is decreased. The plate
voltage which, when applied to the control winding of
current of V16 quickly reaches saturation and drops the
saturable reactor L1 (fig. 10), will overmagnetize the core
bias across R117 to below the cutoff value for V17. The
material and place the inductance of the signal winding at
sharp voltage rise at the plate of V17, as the plate current.
the proper value. This is done to prevent a shift in rf
is reduced to zero, is fed as a positive pulse through
on.
Figure 17. Surge circuit
b. When power is applied to the signal generator, it
capacitor C81 and resistor R79 (fig. 10) to the grid of
potential of + 150 volts dc is applied across series
resistors R115, R116, and R117. The positive voltage
remains with V17 at cutoff and V16 conducting heavily
across R117 causes plate current to flow through V17.
until the plate supply is turned off. Capacitor C86 then
Plate current flow through cathode resistor R118, which
discharges through R113 and R102, and the cycle then
is the common cathode return of both V17 and V16,
is ready to be repeated.
biases V16, to cutoff, since initially its grid is at ground
33