It has an input of 750 volts and the high voltage
It has an input of 750 volts and the high voltage secondary coil which
energizes the plate has an output of 450 watts and develops 1,500 to
3,000 volts. The low voltage secondary coil which heats the filament
develops 10.5 volts. This transformer will supply current for one or
two 50-watt oscillator tubes and it costs about $40.00.
Connecting Up the Apparatus.–Where a single oscillator tube is used
the parts are connected as shown in Fig. 82, and where two tubes are
connected in parallel the various pieces of apparatus are wired
together as shown in Fig. 83. The only difference between the 5 watt
tube transmitter and the 50 watt tube transmitter is in the size of
the apparatus with one exception; where one or two 50 watt tubes are
used a second condenser of large capacitance (1 mfd.) is placed in the
grid circuit and the telegraph key is shunted around it as shown in
the diagram Fig. 83.
CHAPTER XVIII
WIRELESS TELEPHONE TRANSMITTING SETS WITH DIRECT AND ALTERNATING
CURRENTS
In time past the most difficult of all electrical apparatus for the
amateur to make, install and work was the wireless telephone. This was
because it required a _direct current_ of not less than 500 volts to
set up the sustained oscillations and all ordinary direct current for
lighting purposes is usually generated at a potential of 110 volts.
Now as you know it is easy to _step-up_ a 110 volt alternating current
to any voltage you wish with a power transformer but until within
comparatively recent years an alternating current could not be used
for the production of sustained oscillations for the very good reason
that the state of the art had not advanced that far. In the new order
of things these difficulties have all but vanished and while a
wireless telephone transmitter still requires a high voltage direct
current to operate it this is easily obtained from 110 volt source of
alternating current by means of _vacuum tube rectifiers_.
The pulsating direct currents are then passed through a filtering
reactance coil, called a _reactor_, and one or more condensers, and
these smooth them out until they approximate a continuous direct
current. The latter is then made to flow through a vacuum tube
oscillator when it is converted into high frequency oscillations Post-newsweek Stations, Houston, Inc. Kprc-tv and
these are _varied_, or _modulated_, as it is called, by a _microphone
transmitter_ such as is used for ordinary wire telephony. The energy
of these sustained modulated oscillations is then radiated into space
from the aerial in the form of electric waves.