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RADIO BROADCAST
This is the interior of the crystal receiver previously described, and, as may be seen, the entire tuning equipment is mounted on a single Bakelite panel. A variable condenser is supplied for fine tuning and a lattice wound coil is used where wa\'e lengths up to 2,500 meters are desired. This feature permits the reception of signals from the United States Government station at Arlington (Radio Va.)
plates of an oscillatory circuit. The inductance is the tuning coil or variometer used to vary the natural frequency of this circuit.
The first step in the operation of your set after your crystal is properly adjusted, consists of varying the inductance in the antenna circuit so that a current of the frequency set
This is the Aeriola Jr. Crystal Receiving Set manufactured by the Westinghouse Electric Manufacturing Company. .Many of these sets have been sold on the strength of the company's broadcasting station WJZ at Newark, N. J., and these are used as receiving sets at that station. They are suitable for receiving waves of from 1 50 to 500 meters, and have an ordinary radius of 25 to 30 miles. They are sold completely equipped, except for the antenna. The cut in the next column shows the interior of this receiving set
up in your antenna by the transmitting station which you wish to hear, passes through the antenna system with the utmost ease.
The inductive value of the antenna system is in some receiving sets varied by means of a switch which cuts in or out small sections of a tuning inductance. Other sets use a variometer which is a special form of inductance so constructed that one half of the inductance opposes the other at minimum adjustment, and at maximum adjustment the two halves assist each other. In some sets the period of vibration of the antenna circuit is controlled by a variable capacity supplementary to the capacity of the antenna itself.
Now that we have our antenna circuit in
exact resonance with the transmitting station by proper adjustment of inductance and capacity, we must utilize the energy flowing in this circuit in order that it may be converted into sound waves. For this purpose a secondary circuit is used which obtains its energy from the antenna circuit. This secondary circuit should be in resonance with the antenna or primary circuit. When a two slide tuning coil is used, one slider varies the antenna wave length and the other the wave length of the secondary circuit. In such a set the same wire is used for both circuits and for this reason is called a direct coupled set.
Other types of receivers use separate windings for the antenna circuit and the secondarx' circuit. An instrument especially designed for this purpose, permitting adjustment of the distance between the primary and secondary circuit, is called a receiving transformer. The energy from the antenna circuit is transferred to the secondary by utilizing the magnetic field 1 have already described to \ou. The magnetic energy set up in the antenna inductance not only sets up a countercurrent in its own