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Updated: May 4, 2025
Connecting the oscillator tubes up in parallel means that the two filaments are connected across the leads of the storage battery, the two grids on the same lead that goes to the aerial and the two plates on the same lead that goes to the positive pole of the generator. Where two or more oscillator tubes are used only one storage battery is needed, but each filament must have its own rheostat.
Here they heard the soft purring of a large oscillator tube and the indistinguishable murmur of smoothly running AC generators powered by large contraterrene reactors. The elder Dr. Arcot glanced in surprise at the heavy-duty ammeter in a control panel. "Half a billion amperes! Good Lord! Where is all that power going?" He looked at his son. "Into the storage coils.
Now there are two methods by which a vacuum tube can be used as a modulator and these are: by the absorption of the energy of the current set up by the oscillator tube, and by varying the direct current that energizes the plate of the oscillator tube.
You will observe: that the terminals of the power transformer secondary coil which develops 10 volts are connected to the filaments of the oscillator tubes; that the terminals of the other secondary coil which develops 10 volts are connected with the filaments of the rectifier tubes; that the terminals of the third secondary coil which develops 550 volts are connected with the plates of the rectifier tubes; that the pair of filter condensers are connected in parallel and these are connected to the mid-taps of the two filament secondary coils; that the reactance coil and the third filter condenser are connected together in series and these are shunted across the filter condensers, which are in parallel; and, finally, a lead connects the mid-tap of the 550-volt secondary coil of the power transformer with the connection between the reactor and the third filter condenser.
The size you require for this set has an output of 160 milliamperes and it will supply current for one to four 5 watt oscillator tubes. This size of reactor costs $11.50. Connecting Up the Apparatus.
A 500 Mile C. W. Telegraph Transmitter. For sending to distances of over 200 miles and up to 500 miles you can use either: three or four 5 watt oscillator tubes in parallel as described above, or one 50 watt oscillator tube. Much of the apparatus for a 50 watt tube set is exactly the same as that used for the 5 watt sets.
The Vacuum Tube Oscillator. As explained before you can use any amplifying tube that is made for a plate potential of 100 volts. The current required for heating the filament is about 1 ampere at 6 volts. A porcelain socket should be used for this tube as it is the best insulating material for the purpose. An amplifier tube of this type is shown at H and costs $6.50. The Storage Battery.
Much of the apparatus for a 50 watt oscillator set where either one or two tubes are used is of the same size and design as that just described for the 5 watt oscillator sets, but, as in the C. W. telegraph sets, some of the parts must be proportionately larger.
The disadvantageous features are that: a battery current is not satisfactory, its circuits are somewhat more complicated, and the oscillator tubes burn out occasionally. There is, however, a growing tendency among amateurs to use continuous wave transmitters and they are certainly more up-to-date and interesting than spark gap sets.
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. In time past the most difficult of all electrical apparatus for the amateur to make, install and work was the wireless telephone.
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