Chicago, U.S.A.



Description: The apparatus supplied under Cat. No. 80435 consisting the following parts:

The following accessories are not supplied with Cat. No. 80435 but may be purchased separately if desired:

Setting Up Apparatus: Place the oscillator on a wooden table or support stand as far removed from pipes and other masses of metal as possible. It will be a great convenience to the demonstrator, and is highly desirable electrically, to clamp the apparatus on a non-magnetic wooden tripod stand such as our No. 72535. Push the tubes in their sockets, plug the 3 wire connector onto the oscillator and plug the transformer primary connector into, a 110 volt AC 60 cycle lamp socket. The filaments in the tubes should light up immediately. Test the circuit to make sure that it is oscillating by touching the point of a lead pencil to one of the terminals of the inductance. If the circuit is oscillating, small sparks will be produced at the pencil point. In case the circuit Is not oscillating, disconnect the power immediately, as the circuit in a non-oscillating condition will draw an excessive current that will overload both tubes and transformer.

The transmitting antenna arms should not be used until after the cricuit has been tested for oscillations A cut-out switch is located on the primary side of the transforme whereby the line voltage may be disconnected without pulling the cord from its receptacle.

The two binding posts on the base of the oscillator are connecting to a milliammeter of at least a 100 milliampere range. The milliammeter indicates the plate current of the tubes. When the Milliammeter is not in use, the binding posts should be shorted with a short piece of wire.

Transmitting Antennae: Two sets of transmitting antennae are supplied. They consist of four copper-plated brass tubes with a taper plug mounted on one end. The two shorter tubes are intended to be plugged into the tapered receptacles at the ends of oscillator inductance to form the horizontal antenna. The two longer tubes are intended for use with the antenna coupler to form the loose-coupled vertical antenna. Care should be taken to see that these different lengths are used in their proper places only, as to interchange them may cause the circuit to stop oscillating, with possible damage to tubes or transformer. The oscillator and the transmitting antennae are not adjustable for wave length, it being intended that all tuning should be done on the receiver.

Receiving Antenna: The receiving antenna with flashlight bulb detector consists of an insulated center section containing a flashlight bulb and provided at each end with sockets into which copper plated brass tubes may be pushed. The tubes for use with this receiver are equipped with smaller rods or tubes which telescope in the main tubes, thus providing an adjustment in the length of the antenna which constitutes tuning. In use, the adjustments in length should be made equally on both ends so as to keep the lamp approximately at the center.

Thermo-galvanometer: When the thermo-galvanometer, Cat. No. b2665, is used for measuring field strength or indicating resonance, it should be fitted with the antenna arms from the receiver with the detector, To do this, the two short lengths of copper rod, Cat. No. 80451, should be fastened under the binding posts of the galvanometer in such a manner that they project in the same straight line from opposite sides of the meter. The adjustable antenna arms from the receiver may then be slipped over these projections from the meter. Take care when this arrangement is in resonance not to bring it too close to the transmitter, as it is much more sensitive than the lamp detector.

Wavemeter: Before using the wavemeter, Cat. No. 80437, it should be mounted on an insulating base. A flashlight bulb should be shunted across a few centimeters of the wavemeter inductance, or a neon lamp should be attached to one end of the inductance to indicate when the wavemeter is in resonance with the transmitter. A mounting clip, Cat. No. 80438, provides a convenient means of attaching the flash- light lamp. Care must be taken not to hold the wavemeter too close to the transmitter when the two are in resonance or the indicating lamp on the wavemeter may be burned out.

Coupling Loop: The "coupling loop" is-plugged into the socket in the base of the transmitter so that its single turn can be adjusted in Position relative to the oscillator loop, by turning in the socket. Plug one of the long antenna Into the upper end of the coupling loop and the other long one into the same socket from beneath, To do this allow the base to protrude Over the edge of the stand or table.

Lecher Wire Experiment: In performing the Lecher Wire experiments, the antenna coupling loop should be plugged into one of the receptacles in the base of the oscillator and the copper wires should be attached to the coupler above and below the loop. The oscillator must, of course, be clamped down to the table or stand when performing this experiment.

The foregoing are general directions and precautions for the setting up and operating of the Short Wave Radio Demonstration Apparatus. For more specific directions as to the various experiments which may be Performed refer to the reprint from the May 1922 issue of "School Science and Mathematics", Vol. XXIX, No. 5, on "An Apparatus for Demonstrating the Fundamentals of Radio".

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