US1334087A - System for producing oscillations - Google Patents

Description

A. N. GOLDSMITH AND J. WEINBERGER.

' SYSTEM FOR PRODUCING OSCILLATIONS.

APPLICATION FILED MAR. 23, I918.

1 ,334,087, f Patented Mar. 16, 1920.

Fig.1.

AA A AAAAA Inventors: I fllfred. N.Goldsm1t.h Julius Weinberger,

Their Attorney- UNITED STATES PATENT OFFICE.

ALFRED N. GOLDSMITH AND JULIUS WEINBERG-ER, OF NEW YORK, N. Y., ASSIGNORS TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK. I

SYSTEM FOR PRODUCING OSCILLATIONS.

3 To all whom it may concern:

Be it known that we, ALFRED N. GOLD- SMITH and Jams WEINBERGER, citizens of the United States, residing at New York, in the county of New York, State of New York, have invented certain new and useful Improvements in" Systems for Producing Oscillations, of which the following is a specification.

. Our present lnvention relates to the production of electrical oscillations and particularly to the application of high frequency oscillations to radio signaling systems.

It has been found that an electron discharge device comprising an incandescent cathode, a cooperating anode, and a discharge controlling member or grid inclosed in an evacuated envelop may be employed for producing high frequency oscillations which are suitable for radio signaling purposes. It has also been found that when oscillations produced in this way are employed for radio transmission the simplest and most convenient way of applying them to the radiating system is to include the usual plate circuit inductance directly in the antenna circuit. We have found, however, that with the usual circuit arrangements employedfor producing oscillations with an electron discharge device the efii ciency of operation depends largely upon the values of the capacity, inductance and resistance of the oscillating circuits. In other words, for any given device, there is a certain adjustment of the values of these constants which will give the maximum output and the maximum efliciency. When the antenna is made a part of the system which produces the oscillations the capacity and resistance of the system are determined largely by the capacity and resistance of the antenna and the frequency of the oscillations is then adjusted to the desired-value by varying the inductance. Under such conditions it will be found thatthe values of capacity, resistance and inductance thus imposed are notthe values which would give maximumoutput and maximum efficiency for the particular device used.

The object of our invention is to overcome this disadvantage and provide a system of connections whereby the constants of the oscillating system may be made independent of the antenna constants and may be ad- Specification of Letters Patent. t t 1 1920, Application filed March 23, 1918. Serial No. 224,143.

justed' to those values which will give the best etficiency of operation.

glhe novel features which we believe to be characteristic of our invention are pointed out with particularity in the appended claims, the invention itself, however, both as to its organization and method of operation can best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 illustrates the application of our invention to a transmitting system for radio telegraphy, and Fig. 2 shows its application to a transmitting'system for radio telephony.

As indicated in the drawing an electron discharge device 1 which comprises the usual incandescent cathode 2, plate-shaped anode?) and grid 4, is employed for producing the high frequency oscillations which are to be supplied to the antenna 5. In the the approximate middle point 6 of an '1nductance 7 and the anode 3 is connected by means of the variable connection 8 to another point in this inductance through .the condenser 9. The grid 4 is connected to another point in the inductance 7 on the opposite side of the-central point 6 by means of the variable connection 10. The energy for producing the oscillations is supplied by a direct current generator 11 connected between cathode 2 and anode 3. It will be apparent that portions 12 and 13 of the inductance 7 which are included in the plate and grid circuits respectively of the device 1 are inductively coupled to each other and that therefore oscillations will be produced in the circuits of the device. This coupling is variable at will and its value may be chosen within certain limits without afiecting the operation. The frequency of oscillations may be adjusted by varying the condenser 9 and the points of connection 8 and 10 andthe constants of the system at the same time may be adjusted to give the maximum efficiency of operation. The antenna 5 is connected to inductance 7 by the variable connection 14: and the central point 6 of the inductance is grounded at 15. Thus it will be seen that the portion of inductance 7 which is included in the plate circuit of the device is also included in the antenna circuit and that the capacity of the antenna,

lent by the condenser 16 shown in dotted lines, will be in shunt to this inductance. As a result it will be apparent that the capacity of the antenna forms a part of the system in which the oscillations are produced and since this capacity is fixed it may not be possible to secure the adjustment of the con-' stants of the system necessary for the best efficiency of operation. To overcome this disadvantage we compensate for the effect of the antenna capacity by the use of a capacity 17 which is connected in shunt to the. inductance 13 in the grid circuit and which preferably has a value approximately equal to the value of the antenna capacity. When the final adjustments are made the portions '12 and 13 of the inductance 7 will prefer ably have an equal number of turns and v under these conditions the effect of the anradio frequency choke coil is so designed that it is resonant to the frequency of the oscillations produced and under these conditionsit will act as a substantially infinite impedance to the high frequency current,

' and at the same time permit of the free passage of the direct current which feeds the plate circuit.

In order to adapt the system which we have described for producing oscillations to the transmission of modulated signals, and particularly signals modulated by speech currents, the current produced in a telephone transmitter 20 may be applied to the grid circuit of the device by means of an audio frequency transformer 21, as indicated in Fig. 2. The secondary of thetrans former 21 18 preferably shunted by a condenser 22 in order to by-pass the high frequency component of the current in the grid circuit.

The operation of this system is as follows: Suppose the device 1 is producing sustained oscillations of a given amplitude in the antenna. When the telephone transmitter 20 is affected by sound waves voltages corresponding to these waves are induced in the secondary of the transformer 21 and thus directly impressed on the grid 4. The changes in rid potential cause exactly similar and much greater reactance voltages to be produced across the audio frequency choke coil 23 in the circuit which supplies. the energy for producing oscillations. Therefore the plate voltage is varied as these reactance voltages add to or are subtracted from the direct current 'voltage of the generator 11. The radio frequency "0 energy output is directly proportional to the energy input into the plate circuit of the device and the plate energy input is almost directly proportional to the plate voltage. It is therefore clear that as the 7 plate voltage is varied by the reactance voltages across 23 the'radio frequency energy output is varied in almost exact proportion. These are the conditions sought for in radio telephony and the method described gives extremely accurate and eflicient reproduction of speech as Well as being electrically efficient.

While we have described and illustrated our invention with especial reference to the transmission of telegraphic signals by the usual key and to the transmission of sound waves by the aid of the usual telephone transmitter, it will be apparent that our invention is by no means limited to the particular arrangements shown for controlling the antenna current, but that many other modifications may be made in the system of connections used without departing from the scope of the appended claims.

What we claim as new and desire to secure by Letters Patent of the United States, is

1. The combination in a system for producing electrical oscillations of an electron discharge relay having inductively coupled plate-and grid circuits, a third circuit which includes an inductance in the plate circuit of said relay and a capacity which shunts said plate circuit inductance, and a capacity connected in shunt to an inductance in the grid circuit of said relay and having a value corresponding approximately to the capacity of the third circuit.

2. The combination in a system for producing electrical oscillations of an electron discharge relay having coupled plate and grid circuits, a radiating antenna connected to an inductance in the plate circuit of said relay in such a way that the capacity of said antenna shunts said plate circult inductance, and a capacity connected in shunt to an inductance in the grid circuit of said relay and having a value corresponding approximately to the capacity of the antenna.

3. The combination in a system for producing electrical oscillations of an electron discharge relay having coupled plate and grid circuits, a third circuit which includes an inductance in the plate circuit of said relay and means for compensating for the capacity of the third circuit and thereby rendering the adjustment of the system in which oscillations are produced independent of the capacity of the third circuit.

4. The combination in a radio signaling system of means for producing radio frequency oscillations comprislng an electron discharge relay having coupled plate and grid circuits, a radiating antenna directly connected to an inductance in the plate circuit of said relay and means for compensating for the capacity of the antenna and thereby rendering the adjustment of the oscillation producing means independent of the capacity of the antenna.

5. The combination in a system for producing electrical oscillations of an electron discharge relay having a cathode, an anode and a grid, an inductance having its approximate central point grounded and connected to the cathode of said relay, adjustable connections between the anode and grid of said relay and points in said inductance on each side of the central point, whereby separate portions of said inductance are included in the plate and grid circuits of the relay, a third circuit which includes the inductance of the plate circuit and a capacity in shunt to the grid circuit inductance hav- 'ing a value corresponding approximately to the capacity of the third circuit.

6. The combination in a system for producing electrical oscillations of an electron discharge relay having a cathode, an anode and a grid, an inductance having its approximate central point grounded and connected to the cathode of said relay, adjustable connections between the anode and grid of said relay and points in said inductance on each side of the central point whereby separate portions of said inductance are included in the plate and grid circuits of the relay, a radiating antenna directly connected to the plate circuit inductance and a capacity in shunt to the grid circuit inductance having a value corresponding approximately to the capacity of the antenna.

In witness whereof we have hereunto set our hands this 18th day of March, 1918.

ALFRED N. GOLDSMITH. JULIUS WEINBERGER.

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