University of Santa Clara - Redwood Yearbook (Santa Clara, CA)

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THE REDWOOD 11 wires placed on the ground, under the surface, or suspended a few feet above the ground running parallel to the an- tennae. The earth connection is as im- portant, if not more so, than the aerial. In concluding I will say that Wire- less Telephony can be received on any Audion Receiving set, and on a Crys- tal set, provided that the oscillations are well modulated and the transmit- ting station sufficiently close. The Radio Engineer has a very broad and comparatively new field before him. Sending pictures through the ether is in the process of beginning. And sending electrical energy, in worth while quantities and small dissi- pation losses, without wires, will some day be mastered by a Radio Engineer. Bear this in mind. Radio is not the mysterious something which most peo- ple think ; it is an exact Science.

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10 THE REDWOOD grid voltage causes a great variation in the electron flow from the filament to the plate. A slight improveme nt is to place the microphone inductively in the grid circuit by means of a transformer having a high ratio between the prim- ary and the secondary, in order to step up the voltage of the microphonic vari- ations before placing them on the grid. This means is known commonly as the absorption method. A very superior form of modula- tion is known as the constant current system. By this is meant that the plate current of the oscillator is not varied by modulating the grid potential of the tube, but the plate supply is regulated by the results of an output of another Audion Valve, whose grid current has been changed by a microphone in its circuit. In other words, if a constant if the supply of the tube nearest the source of current is fed to two tubes with their plates wired in parallel, and source is varied, a slight potential drop will be effected on the plate of the sec- ond Audion, which will vary the ampli- tude of its oscillations. The method of modulation, where a separate tube is used as a modulator and another as the oscillator, is called the Heissing System. There are several other appliances used in a telephone set, which will be merely enumerated as their functioning will appear obvious: A motor genera- tor, which will supply from 500 to 1500 volts direct current for plate potential, depending upon the size and range of the set. A Voltmeter is required to measure this. A filter circuit is needed to smooth out the ripples of this supply so that a nearly constant amplitude di- rect current may be had. This devise is composed of two II 2 Henry choke coils and two high voltage test con- densers, which are shunted across the coils. A twelve volt Storage Battery is ne- cessary to light the filaments. A Ther- mo-couple or a Hot wire ammeter of suitable range is needed to measure the radiation current in the aerial. This meter must not be of the ordinary mag- netic type as the radio-frequency cur- rents would not go through the arma- ture coil, and a high frequency current stays on the outside of the conductor; consequently, the meter would give a reading which would be correct only for such an instrument of this type with one turn on the armature coil. Before closing, the purpose of the aerial will be stated. Its function is two fold: (1) To radiate energy in the form of electro-magnetic waves; (2) To absorb part of the energy radiated by a distant transmitter; briefly it is that of sending out the impulses and of receiving them. There are four gen- eral types of antennae suitable for transmission, viz. : the vertical or fan type, the umbrella aerial, the inverted L flat top antenna, and the T aerial. The vertical and umbrella antennae radiate well in all directions, while the flat top styles are slightly directional, that is, they radiate the current better in one direction than in another. How- ever, since all aerials are governed by the following two conditions all types find a use: (1) By the length of the wave to be radiated; (2) By the space available for erection. The connection from the transmit- ting apparatus to the earth should be as direct as possible and the conductor ought to be one of high conductivity. The ground connection is sometimes a water pipe, buried plate or a system of

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Mission Bells of Santa Clara E mellow tKroated bards of Orpheus, CKime fortK your peaceful call. The misty gray Is softly fallen o ' er a troubled world And youthful shadows flit in silent play. With strained ear I list for your refrain; But all is still save yonder rustling palm, Swayed gently by the lazy evening breeze, And mystic olive chanting Nature ' s psalm. Lo! NIow your soothing voice is heard, how soft! Celestial cymbals tuned to earthly key; Sweet sounds sublime, intone the hallowed hour. Enchanting echoes of eternity. DONALD J. PIERR 12