Vietnam or Thailand ? Vote for the TOP Country of the Week !
Updated: May 21, 2025
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.
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.
For this telephone transmitting set you need: one aerial ammeter; one tuning coil; one telephone modulator; one aerial series condenser; one 4 cell dry battery or a 6 volt storage battery; one microphone transmitter; one battery switch; one grid condenser; one grid leak; two 5 watt oscillator tubes with sockets; one blocking condenser; one oscillation choke coil; two filter condensers; one filter reactance coil; an alternating current power transformer, and two 20 watt rectifier vacuum tubes.
This latter device may be either a telephone induction coil, a microphone transformer, or a magnetic modulator; the first two of these devices step-up the voltage of the battery current and the amplified voltage thus developed is impressed on the oscillations that surge through the closed oscillation circuit or the aerial wire system according to the place where you connect it.
In the wireless telephone transmitters for long distance work which were shown and described in the preceding chapter a battery is used to energize the microphone transmitter, and these two elements are connected in series with a microphone modulator.
In the first way the secondary terminals of the modulator are shunted around the grid leak in the grid circuit as at A, and in the second the secondary terminals are connected in the aerial as at B. Where an induction coil or a microphone transformer is used they are shunted around a condenser, but this is not necessary with the magnetic modulator.
In the wireless telephone transmitters for long distance work which were shown and described in the preceding chapter a battery is used to energize the microphone transmitter, and these two elements are connected in series with a microphone modulator.
Since the microphone current is absolutely distinct from the oscillating currents surging through the coil of the transformer a very small direct current flowing through a coil on the latter will vary or modulate very large oscillating currents surging through the former. Operation of the Vacuum Tube as a Modulator.
It represents, in the phrase of the inventor, the finger laid upon the throttle-valve of a steam-engine. A minute force becomes the modulator of a much greater force, and thus from imperceptible becomes conspicuous.
The transmitter was completely 'home brew', consisting of a metal 6L6 Franklin oscillator on 3.5 MHz followed by two more 6L6s doubling to 14 MHz. In the final amplifier stage Harry used a Telefunken pentode, the famous and very efficient RL12P35 which was used in the German tank transmitters in all stages, oscillator, P.A. and audio amplifier/suppressor grid modulator.
Word Of The Day
Others Looking