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The higher the negative charge on the grid the smaller will be the number of electrons that will reach the plate and, of course, the smaller will be the amount of current that will flow through the tube and the headphones from the B battery.
While no sound can be heard in the headphones at the receiving station so long as the points of the key are not in contact, when they are in contact the oscillations are modulated and sounds are heard in the headphones that correspond to the frequency of the buzzer in the key circuit. The Operation of C. W. Telegraph Transmitters with Direct Current.
They had landed in a forest, of sorts, and the rocket-blasts had burned away everything underneath, down to solid soil. In a circle forty yards about the ship the ground was a mass of smoking, steaming ash. Beyond that flames licked hungrily, creating more dense vapor. Beyond that still there was only coiling smoke. Cochrane's headphones yielded Babs' voice, almost wailing: "Mr. Cochrane!
They all acceded laughingly to this proposition, and a few minutes later filed into the room where the doctor kept his radio apparatus. His set was equipped with a loud talking device, so that individual headphones were not necessary. With a few touches he adjusted his coils and condensers, and had no difficulty in picking up the broadcasting station.
For this set you require: one variocoupler; two variometers; one .001 microfarad variable condenser; one .0005 microfarad variable condenser; one 2 megohm grid leak resistance; one vacuum tube detector; one 6 volt A battery; one 200 ohm potentiometer; one 22-1/2 volt B battery; one .001 microfarad fixed condenser, and one pair of 2,000 ohm headphones.
When you set up the variometers place them so that their stators are at right angles to each other for otherwise the magnetic lines of force set up by the coils of each one will be mutually inductive and this will make the headphones or loud speaker howl.
But materials were hard to find and very expensive. Two items one had to buy: valves and headphones. "I asked my friend where he had found the sheet metal to make the plates of the capacitor. He took me to a row of small shops which had a metal-faced ledge below the shop window. The metal was thin and seemed easy enough to remove.
She started for it at four gravities acceleration, and Joe got his headphones to his ears and lay panting while he waited for the figures and information he had to have. He got them. When the four-gravity rockets burned out, the tug's crew painstakingly adjusted the ship's nose to a certain position. They flung themselves back into the acceleration chairs and Joe fired a six-g blast.
This done shunt the potential around the A battery and connect the sliding contact to the or zinc pole of the B battery and the + or carbon pole of this to one terminal of the headphones, while the other terminal of this leads to one of the posts of the second variometer, the other post of which is connected to the plate of the detector tube.
If you want to add an amplifier tube then connect it to the posts instead of the headphones as described in the foregoing set. All receiving sets that receive over a range of wave lengths of from 150 meters to 3,000 meters are called intermediate wave sets and all sets that receive wave lengths over a range of anything more than 3,000 meters are called long wave sets.
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