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TYPE 1263-B AMPLITUDE-REGULATING POWER SUPPLY
2.2
CIRCUIT.
The elementary schematic diagram (Figure 4) illustrates the prin-
ciples of operation's of the power supply. The output rectifier develops
a negative de potential proportional to the rf amplitude at the oscillator
output.
This potential is applied to the voltmeter amplifier and to one
grid of the first difference amplifier.
An adjustable negative reference
potential is applied to the other grid of the first difference amplifier. An
increase in the negative potential developed by the output rectifier, with
respect to the reference potential, is amplified by the two difference am·
plifiers, and appears as an increased negative potential at the output·
amplifier grid. This reduces the plate current supplied to the oscillator.
Conversely, a decrease
in
output produces an increase in plate current
applied.
This closed-circuit feedback system holds the output close to
a preset level.
An external contactor shorts the reference potential to
effect rf blanking.
With internal 1-kc square-wave modulation, the regulating action
described above continues except that an RC filter is switched in to pass
only the average de from the output rectifier, and the plate supply is
interrupted with a 1-kc square wave. Under these conditions, the average
or carrier level of the oscillator output voltage is regulated.
Variable
resistors in the 1-kc multivibrator circuit permit adjustment of the fre·
quency and duty ratio of the square-wave modulation over a narrow range.
For cw operation, the multivibrator is biased
to
the "on" state and mod-
ulation ceases.
Figure 4. EleT(lentary Schematic for
Type 1263-B Amplitude-Regulating
Power Supply.
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7
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