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Updated: July 8, 2025
Soft iron cores are not used in oscillation inductance coils and oscillation transformers for the reason that the frequency of the current is so high the iron would not have time to magnetize and demagnetize and so would not help along the mutual induction to any appreciable extent. High-Frequency Currents.
The Oscillation Transformer. With an oscillation transformer you can tune much more sharply than with a single inductance coil tuner. The primary coil is formed of 6 turns of copper strip, or No. 9 copper wire, and the secondary is formed of 9 turns of strip, or wire. The primary coil, which is the outside coil, is hinged to the base and can be raised or lowered like the lid of a box.
Tuning coils, sometimes called transmitting inductances and oscillation transformers, are of various types. The simplest kind is a transmitting inductance which consists of 25 or 30 turns of copper wire wound on an insulating tube or frame.
Intermediate Wave Set With Loading Coils. For this intermediate wave set you can use either of the short-wave sets described in the foregoing chapter. Approximate Wave Length in Meters in Millihenries Inductance .001 mfd. Variable Mounted Appx. Air Condenser. on Plug These and other kinds of compact coils can be bought at electrical supply houses that sell wireless goods.
Under the sub-caption of Self-induction and Inductance in the beginning of this chapter it was shown that it was the inductance of a coil that makes a current flowing through it produce a strong magnetic field, and here, as one of the constants of an oscillation circuit, it makes a high-frequency current act as though it possessed inertia.
An oscillation circuit, as pointed out before, is one in which high frequency currents surge or oscillate. Now the number of times a high frequency current will surge forth and back in a circuit depends upon three factors of the latter and these are called the constants of the circuit, namely: its capacitance, its inductance and its resistance. What Capacitance Is.
As for tuning, just as changing the length and the thickness of the prongs of a tuning fork varies the frequency with which it vibrates and, hence, the length of the waves it sends out, so, too, by varying the capacitance of the condenser and the inductance of the tuning coil of the transmitter the frequency of the electric oscillations set up in the circuit may be changed and, consequently, the length of the electric waves they send out.
Now the antenna has both electrical capacity and inductance, and when connected up with the apparatus a wireless operator can at will cause it to disturb the magnetic fields surrounding the earth." "You didn't say how high these masts had to be, Bob," put in Mr. Crowninshield. "Are they always the same length?" "Oh, no, indeed, sir," was the prompt response.
But when the positive half of an alternating current is made to flow through a large inductance it acts like a large resistance as before and likewise smooths out the current, but none of its energy is wasted in heat and so a coil having a large inductance, which is called an inductive reactance, or just reactor for short, is used to smooth out, or filter, the alternating current after it has been changed into a pulsating direct current by the rectifier tubes.
Now when you close the switch the voltage from the battery charges the condenser and keeps it charged until you open it again; the instant you do this the condenser discharges through the circuit which includes it and the inductance coil, and the discharge of a condenser is always oscillatory.
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