# United States patent 1233841

United States patent 1233841
United States Patent Office.
Elmer E. Butcher, of Interlaken, New Jersey. Assignor to Marconi Wireless Telegraph Company of America, a corporation of New Jersey.
Means for Receiving Electrical Oscillations. :
| No. 1,233,841. | Specification of Letters Patent. | Patented July 17, 1917. |
| Application filed May 12, 1914. Serial No. 837,988. |||
To all whom it may concern:
Be it known that I, Elmer E. Butcher, a citizen of the United States, and a resident of Interlaken, in the county of Monmouth, State of New Jersey, have invented certain new and useful Improvements in Means for Receiving Electrical Oscillations, of which the following is a specification.
The general object of my invention is to provide simple means by which signals produced by electrical oscillations may be made audible, and whereby they may be considerably amplified.
My invention may be applied to the detection of any electrical oscillations, no matter how produced, and may be used in connection with systems for wireless or wire telegraphy or wireless or wire telephony. One of the uses in which my invention finds utility is the detection of continuous or undamped oscillations at the receiving end of a wireless telegraph system, although this is not the only use to which it may be put.
I accomplish the object of my invention by providing means whereby one or more of the constants of one of the circuits at the receiving end of the system may be periodically and progressively varied, so as to put this circuit into and out of a condition of resonance with the received oscillations.
I shall illustrate and describe my improved receiving means in connection with a system in which continuous or undamped oscillations are used, and in which the constant that is varied is the capacity of the circuit, although it will be understood that the inductance may be varied to secure the same effects, or both the capacity and inductance may be periodically increased and decreased.
In the drawings accompanying this specification I have shown in Figure 1 the receiving end of a wireless telegraph system, using undamped oscillations, embodying my invention. In Figs. 2 and 3 I have shown modifications thereof. In Fig. 4 I have shown a form of condenser I may use, and in Fig. 5 I have shown the method of applying this condenser to circuits in which damped oscillations have been received, so that they may be used for the reception of either damped or undamped oscillations.
Referring to Fig. 1, 1 is the aerial; 2 is the aerial tuning inductance and the primary of an oscillation transformer; 3 is a variable condenser; the aerial is earthed at 4, as usual. The secondary of the oscillation transformer is shown at 5, the coupling being preferably a loose one. Connected to the secondary of the oscillation transformer are a revolving condenser 8 and an indicating instrument such as a telephone, 6, which latter is preferably shunted by a variable condenser 7. The revolving condenser is driven by a motor or other suitable source of power 9.
The construction of the revolving condenser may be seen in Fig. 4, Fig. 4$^a$ being a sectional view, and Fig. 4$^b$ an end view thereof. The revolving condenser consists essentially of a frame 10 supporting a plurality of stationary plates 11, as shown in Fig. 4$^b$. Interleaved between the stationary plates are revolving plates 12, which are mounted upon the shaft 13 of the motor 9. It will be apparent that, as the revolving plates rotate, the capacity of the condenser increases to a maximum and decreases to a minimum, periodically. These are any suitable shape, but are preferably so formed as to give a constant increment of capacity for a constant rate of rotation.
If, therefore, the inductance 5 and the capacity 7 be adjusted to certain values, the secondary circuit will be in resonance with the aerial circuit for a given position or value of capacity of the revolving condenser 8, and if the condenser be revolved by means of the motor 9, the secondary circuit will be thrown into and out of resonance with the aerial circuit as of ten as the plates of the revolving condenser pass to a given position.
It is this method of operation that I make use of in detecting signals. The undamped oscillations received are, of course, of such a periodicity that they are beyond the upper limit of audibility and produce no audible signals; by by so adjusting the constants of the secondary circuit that the rotation of the revolving condenser periodically throws the secondary circuit into and out of resonance with the aerial circuit, and audible signal of a frequency proportional to the speed of rotation of the condenser is produced.
In using my improved apparatus the aerial circuit may be as usual, tuned to the wave length of the incoming oscillations. With the revolving condenser stationary, I ​adjust the other constants of the circuit so that the secondary circuit is approximately in resonance with the received oscillations. This may be done either by precalibration of the constants, or by means of a wave-meter and detector. No exact tuning is necessary, however, as the revolving condenser will, within limits, by reason of rotation, find the exact point of resonance.
In Fig. 2 I have shown a modification of my apparatus, which consists in placing the revolving condenser in another secondary circuit containing the indicating instrument. In that figure the aerial is shown a 1, the aerial tuning inductance at 2, the aerial series condenser at 3, the aerial being earthed at 4. The primary of the oscillation transformer is shown at 2$^a$. At 14 I have shown a coupling coil connected in series in the aerial circuit, which coil is in inductive relation with the secondary 15, which secondary is shunted by the revolving condenser 8. The relation of this secondary circuit to the aerial circuit may be direct or conductive, as well as inductive. Any convenient detecting secondary circuit may be used, as for instance that illustrated, which includes a telephone or other indicating instrument 6 which may be shunted by condenser 7, a variable condenser 16, and a crystal or other detector 17. The latter is not essential, although I prefer to use a detector because of its effect upon the operation of the telephone. In the operation of the apparatus shown in Fig. 2, the aerial circuit is tuned to the wave length of the incoming oscillations, and the circuit containing the revolving condenser is adjusted so that for certain positions of the revolving condenser this circuit will be in resonance with the aerial circuit. In this way, when the condenser is revolved, at certain times the energy will be diverted from the detector circuit and caused to flow through the revolving condenser circuit, thus producing, by periodic variations of the constants of the revolving condenser circuit, a weakening and strengthening of the energy pulses in the detecting circuit and consequently audible signals of a frequency proportional to the speed of the condenser.
In Fig. 3 I have shown another modification of my apparatus which consists in placing the revolving condenser in the aerial circuit. Referring to Fig. 3, the aerial is shown at 1, the aerial tuning inductance at 2, the primary of the oscillation transformer at 2$^a$. In series with the aerial is connected the revolving condenser 8, which is connected to the earth at 4. The secondary circuit may be of any suitable type and may contain the secondary of the oscillation transformer 5, a telephone or other indicating instrument 6 which may be shunted by a variable condenser 7, and any suitable detector 17, which, however, may be omitted. In this construction the aerial is periodically thrown into or out of resonance with the received oscillations, thus producing pulses in the detecting circuit of a frequency proportional to the speed of rotation of the revolving condenser.
In Fig. 5 I have shown an application of the revolving condenser to a circuit ordinarily used for the reception of damped oscillations. When arranged as shown in this figure the circuit may be used to receive damped oscillations if the revolving condenser be stopped at a point of suitable capacity; or it may be used to receive undamped oscillations if the revolving condenser be set in motion. This arrangement, therefore, is a convenient one for use at stations where both damped and undamped oscillation must be received at different times.
Referring to Fig. 5, 1 is the aerial, 2 the aerial tuning inductance and the primary of the oscillation transformer, 3 the aerial series capacity, and 4 the earth. The secondary of the oscillation transformer is shown at 5, this secondary being shunted by the revolving condenser 8. Connected in the secondary detecting circuit is a detector 17, a telephone or other indicating instrument 6, and a variable condenser 7 shunting the telephone.
While I have illustrated my invention in certain specific forms, I do not wish to be limited to these forms since it will be evident to those skilled in the art that changes in the specific connections may be made without departing from the spirit of my invention. One of these changes, for instance, as I have already indicated, would be the variation of the inductance of the circuit instead of the capacity. This may be conveniently done by the use of a revolving inductance of the variometer type, which may be connected in the detecting circuit, in the aerial circuit, or in another secondary circuit coupled to the aerial.
What I claim is:
1. Means for receiving electrical oscillation of a given frequency comprising a circuit containing the inductance and capacity, and means for periodically and progressively varying the capacity of said circuit to put said circuit into a condition of resonance with the received oscillations at intervals of a frequency other than the frequency of the received oscillations, and a detector associated with said circuit and responsive to the frequency of said intervals.
2. Means for receiving electrical oscillations of a relatively high frequency comprising a circuit containing inductance and capacity, and means for periodically and ​progressively varying the capacity of said circuit to put said circuit into a condition of resonance with the received oscillations at intervals of a frequency less than the frequency of the received oscillations, an a detector associated with said circuit and responsive to the frequency of said intervals.
In witness whereof I have hereunto signed my name in the presence of two witnesses this 11th day of May, 1914.
Elmer E. Butcher
    Witnesses:
       Walter S. Jones,
       Wm. M. Earl.
This work was published before January 1, 1929, and is in the public domain worldwide because the author died at least 100 years ago.
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