a. Power Supply.
There are four separate power supplies in this transmitter.
(1) Exciter rectifier.
This rectifier provides high voltage to the
oscillator, the frequency doubler, and the intermediate power amplifier.
If the tubes are tetrodes or pentodes, voltages for the screen grids as
well as the plate voltages will come from this rectifier.
(2) Bias rectifier.
This rectifier provides the bias for the intermediate
power amplifier, the power amplifier, and the modulator.
(3) High-voltage rectifier. This rectifier provides the plate voltage for the
or pentodes, the screen grid voltage will come from this rectifier.
(4) Driver rectifier.
This rectifier provides both the high voltage for the
plates and the bias voltage for the grids of the modulator driver.
b. RF Stages.
(1) Oscillator. The oscillator stage may be any one of the various types of
oscillators used in transmitters. It will generate a stable RF frequency.
Since there is no bias voltage shown for this stage, the oscillator is
self-biased.
The output of the oscillator stage is coupled to the
frequency doubler.
(2) Frequency doubler. This stage actually serves a dual purpose. First, it
is used to amplify the oscillator output and raise the frequency to the
desired operating frequency. The second function of this stage is to act
as a buffer so that the load of the other stages will not affect the
stability of the oscillator. This stage is self-biased and the output is
fed to the intermediate power amplifier.
(3) Intermediate power amplifier.
This stage is designed to increase
the
power of the signal.
It may also act as a frequency multiplier.
The
stage may consist of a single tube or two tubes in parallel. The bias
for
this stage is supplied by the bias rectifier.
The output of
the
intermediate power amplifier is fed to the power amplifier.
(4) Power amplifier.
This stage will provide the final amplification of the
RF signal before it goes to the antenna.
In addition, the actual
modulation of the RF carrier takes place in this stage. It is here that
the AF signal is superimposed on the RF carrier, causing amplitude
modulation.
The bias for this stage is supplied by the bias rectifier.
The modulated carrier is fed to the antenna for radiation.
c. AF Stages.
(1) Modulation driver. This stage is used to couple the AF voltage from the
speech amplifier into the modulator stage. The driver stage is
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