The Music Trade Review, March 1, 1913, page 28:
CLARENCE D. TUSKA and Leonard D. Fisk, jr., two well-known local amateur wireless operators in Connecticut, working together have constructed an efficient wireless telephone, by means of which conversation has been transmitted through the ether for distances up to twenty miles, and phonograph music has been heard as far away as Springfield. The apparatus, being in cost not out of the reach of the pocketbook of the average amateur, is creating considerable interest in local wireless circles. It eliminates the expense of other successful wireless telephone devices and while its range is small in comparison with that attained by the recent feats of the American Telephone & Telegraph Co., it is said to mark an advancement in the achievements of the wireless amateur.
Mr. Tuska and Mr. Fisk used for their first experiments an ordinary telephone transmitter and while finding that it served at short distances very well, it was a great strain on the voice when used continually. Shouting was necessary to build up enough of a wave to be detected by the receiving apparatus which the young men had built. Therefore they devised a method of hitching a phonograph to the wireless apparatus, letting it do the shouting, the only wear being on the record.
Heard in Springfield.
This method proved so successful that last month Mr. Tuska received a postcard from George U. Readio, who has a radio station in Springfield, saying that he had picked up the photograph music with his ordinary receiving apparatus. He wrote as follows:--
Concerts by Wireless.
Since he succeeded in throwing tones into the air by means of his wireless instruments Mr. Tuska has very often entertained his brother wireless fans of the city by concerts. Sometimes at 9 o'clock he has sent out the signal "QST" which means "all stations attention," and played The "Washington Post March," the "Blue Danube" and the "Boston Commandery." Unfortunately his instruments are not sufficiently perfected to bring back the applause with which the numbers were received.
As his knowledge of the work increased he added to his instruments, until now he possesses at his home, No. 136 Oakland terrace, a very complete set, made by himself. He has a special amateur license and a commercial operator's license, teaches a class in radiotelegraphy at the Y. M. C. A. two nights a week, is a member of the Institute of Radio Engineers, and with Hiram Percy Maxim, another radio devotee, helped in founding the American Radio Relay League, of which he is secretary. As editor of the "QST magazine," which he and Mr. Maxim publish, he is in touch with hundreds of operators throughout the country. Mr. Fisk, another wireless enthusiast who aided the experiments, has a station at his home on Bloomfield avenue in West Hartford.
The wireless telephone which Mr. Tuska has constructed, while easy to explain to those understand the principles of wireless operation, presents difficulties if one's readers have not this knowledge. As the latter class has probably dropped out by this time, content with the knowledge that he has constructed a wireless 'phone that will work, the balance of the article may be safely devoted to a simple an explanation as possible of the apparatus used by him.
The Problems To Be Met.
In the first place, the problem faced by the experimenter in telephony is one of waves. The electrical waves which flow through the air from one station to another in wireless, and operate like little telegraph tickers, the receivers attached to the recipient's ears, are not constant. There are little gaps between each wave, which while not affecting the ticker sounds, translated from dots and dashes into messages, would break up the sound of the voice, and leave out almost as much as they carry. There are holes in the voice, a jumble of sound sometimes bearing a resemblance to human speech, but generally untranslatable, all caused by the little gaps between the waves.
The first requisite therefore is to get a constantly flowing electrical wave which is never interrupted. To get this, several costly methods are available, among them the use of a battery of Audions, an electric light bulb which will be described later, or the use of a high frequency generator. Both of these methods are beyond the reach of the average amateur's pocketbook. Mr. Tuska, using the arc method has built an ingenious machine for the purpose of securing constant waves. In its essentials this consists of two pieces of tungsten of high resistance, which are capable of being very delicately adjusted in relation to each other. The experimenters first use carbon. their point of departure from the "singing arc" circuit, but found that this burned out too frequently. They then used other metals but found that tungsten had all the requirements to make the perfect arc by which a continuous wave could be sent out.
The only objection to this method is the low frequency of the waves. In the American Telephone and Telegraph Company's apparatus, the frequency is so high that the vibrations are far beyond the highest pitch that can be heard by the ear, and all noises other than those of the speaking voice lost. But in the apparatus of Mr. Tuska, the frequency is much less and can be recognized as a humming sound, not however, seriously interfering with the talking.
Wave Not Ideal.
In producing the continuous electrical wave Mr. Tuska was not successful introducing the ideal wave of the equal frequency, as illustrated above by No. 1. instead this wave--like a four-cycle gas engine--gets a fresh electrical impulse once every few vibrations, so that at times the waves taper off almost to nothing before a fresh impulse is given. The waves which his arc circuit produces is represented by No. 2.
Carrying the Voice.
Next comes the problem of throwing the voice out on this wave. The voice, like the electrical wave, consists of vibrations and can be diagrammed. Agitating the air, it will only carry to shouting distance--the problem, therefore, is one of carrying vocal vibrations on the distance traversing vibrations of the electrical wave. Picture, therefore, the wave of sounds being carried pig-a-back on the shoulders of the electric waves and you have some conception of what happens.
Of course the actual sound is not carrried, for it is charged into electrical waves, or rather by its actions changes the electrical waves into its own shape. This is accomplished by an ordinary telephone transmitter.
Inside the Transmitter.
Few people, although they may use the telephone constantly, have any idea of what the inside looks like, or how it works. The transmitter consists of a metal plate, or diaphragm, which the voice waves make vibrate back and forth when they strike it. Behind the diaphragm is a small cell which is full of small grains of carbon. When the diaphragm is thrown back by the voice waves it compresses the carbon particles and allows the current of electricity to pass through them more easily than when it rebounds and allows particles to separate slightly. Thus a series of electrical impulses--strongs and weaks--is set up which operate a magnet in the receiver at the other end of the line, the magnet putting in motion another diaphragm which gives off the sounds of the voice.
As used by Mr. Tuska in his wireless telephone, the transmitter does just same thing. The little electrical waves set up by the alternating resistance and conductivity of the carbon particles of the translator build up the continuous wave sent out of the arc circuit until they resemble No. 1 in the diaphragm. The wave then all has the vibrations of the human voice plus the range of the electrical wave and when received reproduces in the receiver the tones as they were uttered.
The Receiving Station.
The third factor of wireless telephony, is of course, the receiving station. The receiver must be continuously responsive and capable of corresponding with sufficient rapidity to the speech harmonics. Any wireless station can receive Mr. Tuska's messages and music, from the fact that the receivers are exactly the same as telephone receivers. Of course, if wireless receivers were built like telegraph tickers, to register only the dots and dashes, the voice could not be received them.
The receiving apparatus common to all wireless sets consists of some form of detector and a telephone receiver and battery. Experiments in wireless telephony have developed an interesting type detector known as the Aaudion. This consists of a six volt, low-candlepower incandescent lamp, having a small nickel plate, fastened a short distance from the filament, and a "grid" bent from wire placed midway between the two. When the filament is lighted from a battery, it throw off a stream of extremely small particles charged with electricity called "ions." These ions pass through the grid and discharge against the plate. Whenthe aerial is connected to the grid and the plate to the ground, the stream of ions carries that part of the alternating current in the aerial which flows in the same direction across, but does not allow the current tending to pass in the opposite direction. I reality it is a valve or rectifier, opening one way and closing the other: those changing the current from an alternating into an intermittent, direct current, capable of manifesting itself in a telephone receiver.
If this detector is not used, the result is that the waves, pushing and pulling, come so rapidly that the diaphragm of the receiver does not have time to vibrate with them, but stands still. By cancelling all of the negative vibrations of the alternating current, the result is a pulsating direct current which rises and falls but is able to flow through the telephone receiver and produce a motion of the diaphragm with consequent sound waves audible to the ear. It also has the effect of halving the frequency of the current as compared to the alternating current from which the director was divided. The "last" half of the alternating current is dispersed in heat.
Harnessing the Phonograph.
The other interesting piece of apparatus which Mr. Tuska has constructed is the modified phonograph, whereby he was able to lessen the effort of continued talking. He first placed the machine close to the telephone transmitter, but with poor results, as the vibration of the air was too feeble to operate the wireless apparatus. He then replaced the phonograph reproducer with a telephone transmitter, in the diaphragm of which he soldered reproducing styles of the machine. Then by playing a disk operated the diaphragm mechanically and was able to get a strong vibration which equals that obtained by the loudest shouting.
In the search for some means of getting a strong vibration in the transmitter, Mr. Tuska tried many weird experiments, one of which was to bore several holes in a wooden chopping bowl and to fix a telephone transmitter in each hole, connecting them in series. This, however, failed to build up the strong vibration for which he hoped.
The diagram illustrated above shows in a simple manner Mr. Tuska's device for wireless telephones. The current, taken from the lighting circuit's 110-volt alternating current. By means of a transformer he raises the voltage, and the current passes through the condenser, by means of which the oscillations necessary to generate electric waves are set up, and the waves are released by the arcing tungsten at S. The current then passes through the induction coil represented by O, the telephone transmitter being in circuit with the secondary coil, the aerial and the ground.
Mr. Tuska is now taking the science course at Trinity College. He came to the city eight years ago from Nyack, N. Y.