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Updated: May 4, 2025
If the grid resistor on that oscillator went out, for instance, what would it do?" Arcot cocked an eye at the power pack, visualizing the circuits. "Full blast, straight up, and no control. But modern printed resistors don't fail." "That's what it says in all the books." Wade nodded wisely.
For this transmitter you require: one oscillation transformer; one hot-wire ammeter; one aerial series condenser; one grid leak resistance; one chopper; one key circuit choke coil; one 5 watt vacuum tube oscillator; one 6 volt storage battery; one battery rheostat; one battery voltmeter; one blocking condenser; one power circuit choke coil, and one motor-generator. The Oscillation Transformer.
We may have to change the oscillator frequency quite a bit, but a variable condenser will do that. "Now, what results did you get?" Wade shook his head doubtfully. "We all know it's amazing stuff and of course, it must be heavy but still well, anyway, I got a density of 103.5!" "Whewww 103.5! Lord! That's almost five times as heavy as the heaviest metal hitherto known.
The island of Crete in southern Greece was first heard on the air in 1938 when George Zarifis came on 40 metre CW using the callsign SV6SP. His transmitter consisted of a single metal 6L6 crystal oscillator with an input of about 7 watts. For reception he used an American CASE broadcast receiver in which he had fitted a BFO. In a very short period he had about 500 QSOs.
Where a single tube is used as an oscillator and a second tube is employed as a modulator, a reactor, which is a coil of wire wound on an iron core, is used in the plate circuit to keep the high voltage direct current of the motor-generator the same at all times. Likewise the grid circuit reactor is used to keep the voltage of the grid at a constant value. Connecting up the Apparatus.
But in all of the transmitters described of whatever type or kind the same fundamental device is used for setting up sustained oscillations and this is the vacuum tube. The Operation of the Vacuum Tube Oscillator.
The only differences between this and the preceding transmitter are: the magnetic modulator, if you use one, should have an output of 3-1/2 to 5 amperes; you will need two 50 watt oscillator tubes with sockets; two 150 watt rectifier tubes with sockets; an aerial ammeter that reads to 5 amperes; three 1 mfd. filter condensers in parallel; two filter condensers of 1 mfd. capacitance that will stand 1750 volts; and a 300 milliampere filter reactor.
Distances of from 200 to 500 miles can be successfully covered with a telegraph transmitter using two, three or four 5 watt oscillator tubes in parallel. The apparatus needed is identical with that used for the 100 mile transmitter just described. A 500 to 1,000 Mile C. W. Telegraph Transmitting Set.
The way the positive and negative voltages of the oscillations which are set up by the incoming waves, energize the grid; how the oscillator tube clips off the negative parts of them, and, finally, how these carry the battery current through the tube are shown graphically by the curves at D. How the Vacuum Tube Acts as an Amplifier.
All of the apparatus for this C. W. telegraph transmitting set is the same as that described for the 100 and 200 mile sets but you will need: one or two 50 watt oscillator tubes with sockets; one key condenser that has a capacitance of 1 mfd., and a rated potential of 1,750 volts; one 0 to 500 milli-ammeter; one aerial ammeter reading to 5 amperes, and an A. C. power transformer for one or two 50 watt tubes.
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