Modulation

“ Even more, even if there is a field of forces which can propagate at large distance through any kind of material, in order to transmit information, modulation of the energy, depending on the information, is also necessary. ”

“ Modulations are really governed by the same laws which apply to any succession of harmonies whatsoever, and the possibilities of modulatory device are in the end chiefly dependent upon intelligible order in the progression of the parts. It is obvious that a large proportion of chords which can succeed each other naturally—that is, without any of the parts having melodic intervals which it is next to impossible to follow—will have a note or notes in common; and such notes are as useful to connect two chords in the same key as they are to keep together a series which constitute a modulation. ”

“ As he follows the pointer up and down the new scale he is soon taught to understand that a new sound is wanted to be the te of the new doh, and thus learns, by the 'feeling' of the sounds, not by any mere machinery of symbols, what modulation is. When he has been made familiar with the change from scale to scale on the modulator, he finds in the printed music a sign to indicate every change of key. Thus the changes between tonic and dominant in the following chant are shown as follows (taking the soprano part only) ”

“ Here you trace one winding and creeping, by soft and subdued steps, through the labyrinth of sweet sounds; then another drops, with delicious trickling falls, from the highest compass to the level of the rest; then one seems at length to extricate itself; then another, in imitative successive cadences; they seem as silver threads that gradually unravel themselves, and then wind round the fine deep-toned bass which has scarcely swerved from its steady dignity during all their modulations, and filling up the magnificent diapason, burst into a swelling final cadence, which has no name upon earth. ”

“ In certain of its phenomena, now classified as electrical, this dual impulse is noted and its action is called “closing the circuit” and “breaking the circuit.” This same dual impulse or tendency to embrace and separate—embrace and separate—obtains throughout the entire cosmos, proving the universality of electrical action. Ether, fire, air, water, earth, sound, sensation, light, form, color, smell, food, thought are all known to be modes of motion—rates of vibration. Motion of what? Rate of vibration of what?—Of the infinite, integral, component electrons of the one universal substance. ”

“ RESISTANCE, HIGH FREQUENCY.--When a high frequency current oscillates on a wire two things take place that are different than when a direct or alternating current flows through it, and these are (1) the current inside of the wire lags behind that of the current on the surface, and (2) the amplitude of the current is largest on the surface and grows smaller as the center of the wire is reached. This uneven distribution of the current is known as the skin effect and it amounts to the same thing as reducing the size of the wire, hence the resistance is increased. ”

“ If we now stimulate the end A by a tap, or better still by rapid torsional vibration, a "current of action" will be found to flow in the wire in one direction. Stimulation of B on the other hand, gives rise to a current in the opposite direction. The object of the block C is to prevent the molecular disturbance produced by stimulus at one end of the wire from reaching the other. ”

“ It may therefore be that the variations of resistance which are observed at contacts between all conductors, from the best to the worst, are all made up, though they appear to pass through gradual and continuous changes, of innumerable minute makes-and-breaks of molecular contact. ”

“ In the last chapter we have seen that a wire often falls, especially after resting for a long time, into a state of comparative sluggishness, and that this molecular inertness then gradually gives place to increased mobility under stimulation. As a consequence, an increased response is thus obtained. I give in fig. 74, b, a series of responses to uniform stimuli, exhibited by platinum which had been at rest for some time. This effect is very clearly shown here. So we see that in a substance which has previously been in a sluggish condition, stimulation confers increased mobility. ”

“ A2 and B2 represent the intermittent currents produced, 4 impulses of B2 being made in the same time as 5 impulses of A2. The line A2 + B2 represents the resultant effect upon the main line when the reeds a and a1 are simultaneously caused to make and break the same circuit, and from the illustration you will perceive that the resultant current, whilst retaining a uniform intensity, is less interrupted when both reeds are in operation than when one alone is employed. ”

“ This fact becomes still more evident when we discover how invariably response is increased by increasing the intensity of stimulus.
Electrical response is due, as we have seen, to a molecular disturbance, the stimulus causing a distortion from a position of equilibrium. In dealing with the subject of the relation between the disturbing force and the molecular effect it produces, it may be instructive to consider certain analogous physical phenomena in which molecular deflections are also produced by a distorting force. ”

“ It had long been my belief that human thought consists basically of atomic or molecular motion, convertible into ether waves of radiant energy like heat, light, and electricity. This belief had early led me to contemplate the possibility of telepathy or mental communication by means of suitable apparatus, and I had in my college days prepared a set of transmitting and receiving instruments somewhat similar to the cumbrous devices employed in wireless telegraphy at that crude, pre-radio period. ”

“ The voltage of the grid of the modulator tube is varied by the secondary coil of the induction coil or microphone transformer, above described. In this way the modulator tube acts like a variable resistance but it amplifies the variations impressed on the oscillations set up by the oscillator tube. As the magnetic modulator does the same thing a vacuum tube used as a modulator is not needed where the former is employed. For this reason a magnetic modulator is the cheapest in the long run. ”

“ The form of the response curve, stimulus remaining constant, is modified by the molecular condition of the wire. A wire in a sluggish condition shows feeble response, the recovery being also slow. The same wire after it has been vibrated for a time exhibits a stronger response. Longer time is required for recovery from the action of a stronger stimulus. ”

“ The names of the sounds are so placed on the modulator as to show, accurately, the true positions of the sounds in the natural (untempered) scale. When the class can, with some readiness, sing the sounds as the teacher points to them on the modulator, they are introduced to exercises printed in a notation formed out of the initials of the scale-names ”

“ For quantitative measurement it is necessary to have the intensity of stimulus maintained uniform, or increased or decreased in a definite manner. Instead of a tap, the stimulus of torsional vibration is more satisfactory. By maintaining the amplitude of vibration constant, or increasing or decreasing the amplitude, we can either keep the stimulus constant, or increase or decrease it in a quantitative manner. I shall first describe some of the typical results which may be obtained with the simple "straight wire form" of the apparatus. Worked with care it gives consistent and good results. ”

“ The truth is that all the facts alleged can be brought back to a single type: the one stimulus capable of producing different sensations, the multiple stimuli capable of inducing the same sensation, are either an electric current or a mechanical cause capable of determining in the organ a modification of electrical equilibrium. Now we may well ask whether the electrical stimulus does not include different components, answering objectively to sensations of different kinds, and whether the office of each sense is not merely to extract from the whole the component that concerns it. ”

“ If the conductor be large, or the frequency high, the central portion of the conductor carries little if any current, hence the resistance is therefore greater for alternating current than for direct current. ”

“ When the potential of a body is rapidly alternated it is certain that the structure is jarred. When the potential is very high, although the vibrations may be few—say 20,000 per second—the effect upon the structure may be considerable. ”

“ By carrying your thoughts still further you will understand that when a large number of reeds of different pitch or of different rates of vibration are simultaneously making and breaking the same circuit the resultant effect upon the main line is practically equivalent to one continuous current.
Fig. 11.
It will also be understood that the maximum number of musical signals that can be simultaneously directed along a single wire without conflict depends very much upon the ratio which the “make” bears to the “break;” ”

“ Short waves, long waves, micro-waves, frequency-modulated waves, amplitude-modulated signals, every conceivable type of radiation signal, was beamed at the small, invisible, hurtling objects as they swung madly about the globe. ”

“ Upon consideration of the subject, however, I saw that the experiments could not be conducted in the ordinary way, for the following reason: The law of audibility of the telephone is precisely analogous to the law of electric induction. No effect is produced during the passage of a continuous and steady current. It is only at the moment of change from a stronger to a weaker state, or vice versa, that any audible effect is produced, and the amount of effect is exactly proportional to the amount of variation in the current. ”

“ It would seem rather that a disturbance throughout the entire circuit is at once set up by a series of vibrations or impulses communicated from particle to particle, and along the strange net-work of nerves. One set of chemical elements have a tendency to develope themselves at that point where vibration is first communicated to the mass from a better conductor than it is, and another set at the point where it passes from the body to a better conductor than itself. ”

“ Incidentally we gain, by the use of very high frequencies, many advantages, such as a higher economy in the light production, the possibility of working with one lead, the possibility of doing away with the leading-in wire, etc. ”

“ Again, as another example, let the required nature be the communication of quality, without intermixture of substance. The instance of light will afford or constitute one species of communication, heat and the magnet another. For the communication of light is momentary and immediately arrested upon the removal of the original light. But heat, and the magnetic force, when once transmitted to or excited in another body, remain fixed for a considerable time after the removal of the source. ”

“ Mirrors, or adding machines? You can't make an audio amplifier of a three million gain."
"I know it—at least not a practical one. But, we can probably use our audio modulator to modulate a radio frequency, and then modulate the driver with the RF. Then we hang a receiver onto the detector gadget here, and collect RF, modulated, just like a standard radio transmission, and amplify it at RF, convert it to IF, and detect it to AF. Catch?" ”

“ Balancing effect when both the ends are stimulated simultaneously.
Experiment to exhibit the balancing effect.—If the wire has been carefully annealed, the molecular condition of its different portions is found to be approximately the same. If such a wire be held at the ‘balancing point’ (which is at or near the middle) by the clamp, and a quick vibration, say, of 90° be given to A, an upward deflection will be produced; if a vibration of 90° be given to B, there will be an equal downward deflection. ”

“ All things equal, then, a telephone transmitter will be so much the more potent in proportion as the lines set in motion by the vibrations of the disk and meeting the bobbin wire are greater in number. In like manner, a receiver will be so much the more potent in proportion as the lines of force, set in motion by variations in the induced currents that are traversing the bobbin and meeting the disk, are more numerous. ”

“ Thus, to select an example from among physical effects, the vibratory phenomena that occur in telephone transmissions, under the influence of a very feeble electric current, show us that the molecular constitution of a solid body is extremely variable, although within slight limits. ”

“ I can invite any expert to perform an experiment such as is illustrated in Fig. 15, which shows the classical Hertz oscillator and my grounded transmitting circuit. It is a fact which I have demonstrated that, altho we may have in the Hertz oscillator an activity thousands of times greater, the effect on the receiver is not to be compared to that of the grounded circuit. This shows that in the transmission from an airplane we are merely working thru a condenser, the capacity of which is a function of a logarithmic ratio between the length of the conductor and the distance from the ground. ”

“ Motion of either source or receiver can alter frequency; motion of receiver can alter apparent direction; motion of the medium can do neither.
But the question must be asked, can it not hurry a wave so as to make it arrive out of phase with another wave arriving by a different path, and thus produce or modify interference effects? ”