US1730994A - Radio frequency amplification system - Google Patents

Description

Oct. 8, 1929, F". J. BULLWANT RADIO FREQUENCY AMPLIFICATION SYSTEM Filed Nov. 5, 1925 Patented Oct. 8, 1929 UNITED STATES PATENT OFFICE FRANCIS J. BULLIVANT, ST. LOUIS, MISSOURI, ASSIGNOR TO VALLEY ELECTRIC COMPANY, OF ST. LOUls, MISSOURI, A CORPORATION OF DELAWARE RADIO FREQUENCY AMPLIFICATION SYSTEM Application filed November 5, 1925. Serial No. 67,112.

This invention relates to radio frequency amplification systems and more particularly to inulti-stage systems utilizing audions or electron tubes.

One of the objects of this invention is to provide means for preventing undesirable oscillations in such a circuit, more especially in the range of higher wave lengths as now used in broadcasting.

Another object of this invention is to provide means for suppressing any such oscillations which may be or tend to set up and by a potential action rather than by'a capacity action.

Further objects will appear from the detail descriptiontaken in connection with the accompanying drawing, in which:

Figure 1 is a diagram showing a radio. frequency amplification system embodying this invention;

Figure 2 is a side elevation of a radio frequency transformer showing the coupling element;

Figure 3 is a section on 2; and I i I Figure 4 is a detail showing anotherembodiment of this invention.

In an application of Victor H. Laughter, Serial NOFGTJOT tiled of even date herewith, a coupling element is connected with the gr d of each audion in the radio frequency circuit of a radio frequency amplification system and such coupling element is electro-magnetically as well as electro-statically coupled with the plate circuit so as to apply to the grida potential which is opposed to the potential of the disturbing oscillation. More specifically this coupling element comprises an open ended coil which is magnetically as well as electro-statically coupled to the radio frequency transformer in the output circuit of the'audion, to the grid of which the coupling element is connected, and this coil is arranged for adjustment with respect to the transformerso as to provide means for varying the potential impressed on the grid.

In accordance with this invention a coupling element is provided which is coupled with the input circuit of one audion of the radio frequency circuit and is connected with line 3-3, Figure the grid of the succeeding audion. This coupling element is also preferably an openended coil, which in the specific embodiment disclosed is magnetically coupled with the radio frequency transformer leading to the audion and is connected with the grid of the succeeding audion so as to impress a voltage on that grid, The radio frequency transformer to which this coil is coupled is preferably the one preceding the first audion so that it is connected to the grid of the second audion. This coil is arranged for adjustment so as to vary the potential impressed on the grid, and since it is also electro-statically coupled to the transformer, it has an electrostatic tapped coupling thereto so that by adjustment the voltage impressed on the grid can be varied. I Referring now to the accompanying draw ing, and more particularly to Figure 1 which shows a radio-receiving system having two stages of radio frequency and two stages of audio frequency, 1 and 2 designate the amplifier tubes in the radio frequency circuit, the detector tube, and 4 and 5 the amplifier tubes in the audio frequency circuit. The audion tubes are of the usual form having a filament, a grid and a plate. The radio frequency transformers are indicated at 10, 20

and 30, while the audio frequency transformers are indicated at 10 and 50. Associated. with the input circuit of each tube is a variable condenser indicated at 11,21 and 31. The usual grid leak and condenser is shown at 6 and the current controlling rheostats at 7 and 8. Condensers 12 and 22 may. also be provided. The usual connections to the aerial and ground and the A battery, B battery and battery are also indicated.

a As described in the Laughter application referred to, connected with thegrid of each of the audions 1 and 2 in the radio frequency circuit, is a coupling element 9, which as heretofore described, is preferably an openended c0il. This coil is preferably magnetically coupled with the radio frequency transformer between the tube to whose grid it is connected and the succeeding tube, and since it is in close proximity thereto, it is also electro-statically coupled with the transformer coils. The coil 9 is so wound that the voltage set up therein and in'ipressed on the grid will be opposed to the disturbing voltage setting up the oscillation, so that the oscillation will be suppressed. it is furthermore adjustable in order to vary the magnitude of the imp essed voltage in order to balance the objectionable voltage.

Coupled to the transforme 10 is a coupling element 13 which is connected to the grid of the audion 2. This coupling element 13, as heretofore described, is preferably an openended coil which is magnetically coupled with the transformer and since it is in close proximity thereto, is also electro-statically cou pled with the transformer coils. The coil that the voltage set up therein on the grid will be opposed to voltage setting up the oscilla- .1 i -i18 ion, so that the oscillation will be suppressed. it is furthermore adjustable in oroer to vary the magni file of the impressed voltage in i to buce the ob ectionable voltage,

is this invention is also applicable to frequency amplification systems can radio p-oying cylindrical or solenoid coils, preferably toroidal coils are used for the radio freuency transformers. Referring to Figures 2 and 3, both the primary and secondary coils are shown as of toroidal form, the primary being made of sections 1a interposed by the sections 15 of the secondary. These coils are held in proper assembled relation by endpieces 16 having notches 17 for engaging the c :il sections and held together by screw 18 passing through a collar 19. Tape or ribbon 252 may also be provided to further hold the parts together while the end plates are provided with feet for attaching the trans former to its support.

Each of the transformers 20 and has mounted thereon a balancing coil 9 which is carried by a slotted bracket 26 supportingthe coil 9 and held in adjusted position by a screw 2? taking into the end plate; this is fully deribed in the Laughter application referred to. The coil 13 is also supported and adjustable in a similar manner on the transformer 10 by a similar bracket 26 also held in adjusted position by ascrew 27 taking into the end plate. In this way the coil 13 as well as the coil 9 may be adjusted within the field set up bythe primary and secondary coils. By moving the coils radially the voltages set up and impressed on the grid can be varied and adjusted.

It will thus be seen that the invention ac complishes its objects. The provision of the coupling element- 13 impresses on the grid a voltage which will suppress the oscillations set up or tending to be set up. By adjustment of this coil, the voltage impressed on the grid can be varied until the proper balance is obtained. The coil 13 is particularly useful in 1 supplementing the actions of the coils 9 by sition and held in adjusted position.

suppressing oscillations, especially at the higher wave lengths as used in broadcasting, for instance, above lOO meters. The direction of winding of the coil 13 can be readily determined in the same manner as for the coil 9 as described in the Laughter application, for if wound in one direction it will cause suppression of the oscillation, while if wound in the wrong direction the oscillation will not be completely suppressed. In the diagram as shown in Figure 1 and Figures 2 and 3 the turns of the coupling coil 13 as in the coupling coil 9 are in the same direction as those of the primary and secondary of the transformer to which the coil is coupled. It is not, however, necessary to provide a condenser in the lead from either coil to the grid, for a voltage of the proper value can be readily obtained by adjustment of the coil. In view of the fact that the coil 13 as well the coil 9 is an open-ended coil, the coupling to the transformer is an electrostatic as well as a magnetic coupling. Accordingly the phase as well as the magnitude of the voltage applied to the grid is controllable as well as adjustable. Moreover since the coil is coupled electro-statica-lly as well as electromagnetic-ally to the transformer coil or coils, the adjustment provides for varying the position of the coupled coil along the trans- I former coil so as to vary its relation to the potential gradient of the latter coil and thereby adjust its potential elevation relatively thereto. lVhile the adjustment of the coil 13 is critical, the number of turns of this coil is not critical in suppressing oscillations. However, by providing the coupling coil with a number of turns (twelve turns of fine wire being found satisfactory for the coil 13 as well as the coil 9 where the primary has twenty-one turns and the secondary one hundred sixty-five turns, and where the parts are of the relative dimension as shown, when using ordinary audions), the tone quality is improved; accordingly the combination results in a clean, pure tone with a comparatively wide range of selectivity. At the higher wave length the volume as well as se any adjusted position. In this way the coupling coil can be adjusted to the desired po- The coil 13 may also be placed between the coils 14; and 15.

lVhile certain theories have been advanced each having a grid with reference to the operation, it is to be understood that they are not absolutely neces sary to the practical operation of this system; accordingly it is to be understood that this invention is not to be limited to any particular theory of operation. It is further obvious that various changes may be made in details of construction without departing from the spirit of this invention; it is, therefore, to be understood that this invention is not to be limited to the specific details shown and described.

Having thus described the invention, what is claimed is:

1. A multi-stage radio-frequency amplification system comprising, a plurality of audions each having a grid and a plate, input and output circuits, a coil in the input circuit of an audion, and a coil magnetically and electrostatically coupled to said first coil intermediate its ends and connected to the grid of the succeeding audion, said latter coil being adjustable relative to said first coil.

2. A multi-stage frequency amplification system, comprising, a plurality of audions and a plate, input and output circuits, transformer coils in said circuits, a coil magnetically and electrostatically coupled to the output coil of one of said audions and connected to the grid thereof, a coil magnetically and electrostatically coupled to the input coil of a preceding audion and connected to said same grid, and means for adjusting said coupled coils relatively to their respective transformer coils.

3. A multi-stage amplification system, comprising, a plurality of audions each having a grid and a plate, input and output circuits, a coil in the input circuit of an audion, a coil magnetically and electrostatically coupled with said coil and connected with the grid of the succeeding audion, a coil in the output circuit of said second audion, and a coil magnetically and electrostatically coupled with said third coil and connected with said grid of said second audion, one of said grid circuit coils being adjustable relative to its coupled coil.

In testimony whereof I affix my signature this 4th day of September, 1925.

FRANCIS. J. BULLIVANT.

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