US1654976A - Vacuum-tube circuits - Google Patents

Description

Jan. 3, 1928. I

E. w. KELLOGG VACUUM TUBE CIRCUITS Filed 001;. 5, 1922 2 Sheets-Sheet l fnvenon' Edward W/(e// 9 W- ///'s Attorney Jan. 3, 1928.

E. W. KELLOGG VACUUM TUBE CIRCUITS Filed Oct. 5, 1922 2 Sheets-Sheet 2 Inventor-5 Edward Ke// ///Ls Attorney I Patented Jan. 3, 1928.

UNITED STATES PATENT GFFICE.

EDEVARID W. KELLOGG, OF SCHENECTADY, NEW YORK, ASSIGNOE TO GENERAL ELEG- IRIG COMPANY, A CORPORATION 01 NEW YORK.

VACUUM-TUBE CIRCUITS.

Application filed October 5, 1922.

My present invention relates particularly to circuit arrangements for amplifying and detecting high frequency signaling currents by means of three eletrode electron discharge devices employingthe principle of electro static current control, although it is not limited in its application to this method of control, but may be employed with devices embodying the electromagnetic principle of current control.

The object of my invention is to provide improved circuit arrangements whereby the number of separate devices necessary to employ to secure a desired result may be reduced by permitting of the use of a single device to serve different functions.

In the heterodyne reception of continuous wave telegraphic signals by means of elec tron discharge devices, two general methods have been employed known self heterodyne or autodyne and separate heterodyne. In the first of these methods a single device has been employed as detector and generator of local high frequency currents of a frequency differing from the signaling frequency. This has necessitated the use of resonant circuits with the device tuned to a frequency differing from the signal fre quency. As a result the amplification of the signal frequency possible with such an arrangement has been greatly reduced or entirely eliminated particularly in the reception of'long waves.

To overcome this disadvantage the separate heterodyne system has been employed in which a second device has been used as a generator of local oscillations and the oscillations thus generated have been impressed upon the grid or control circuit of the detector. The grid or control circuit of the detector may then be tuned to the signal frequency and amplification of the signal either with or without regeneration may be readily obtained.

I have discovered that results substantially equal to those obtained by the separate heterodyne may be obtained with a single device. To secure such results two separate tuned circuits may be provided in connec tion with the grid or control circuit of the device and separate feed back connections employed from the plate circuit for feeding back energy to these two tuned circuits. As an alternative arrangement, the circuit which is tuned to the local frequency may be asso- Sclial No. 592,605.

ciated with the plate circuit and a feed back connection provided from this tuned circuit to the grid or control circuit in addition to the feed back connection employed for regenerative amplification.

It has hertofore been proposed to employ an electron discharge device both for radio and audio frequency signal amplificz'ition. I have discovered that a device employed for audio frequency amplification may at the same time be employed as an oscillator for generating the local frequency oscillations for separate heterodyne reception thus permitting of the use of all of the devices em ployed in a receiving and amplifying system for two purposes. For example, in a system employing three electron discharge devices, one device may serve for both radio and audio frequency amplification, a second device for audio frequency amplification and generating oscillations, and the third device as a detector and amplifier as in the separate heterodyne system.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation will best be understood by reference to the following description taken in connection with the accompanying d'awing in which Figs. 1 and 2 show diagrammatically two different circuits whereby a single device may be employed as detector, amplifier and oscillator and Figs. 3, 4e and show diagraimuati- Cally different circuit arrangements in which all of the devices employed serve double functions.

In the arrangement illustrated in Fig. 1., an electron discharge device 1 of the three electrode type is shown. The grid circuit of this device includes a resonant circuit 2 which is tuned to the signal frequency and a second resonant circuit 3 which is tuned to the local frequency to be generated. A feed-back coupling coil 4- in the plate circuit furnishes energy to oscillating circuit 3 for generating oscillations and a second feed back coupling coil 5 in the plate circuit which is coupled to the antenna coupling coil 6 or to the tuned circuit 2 or both, and permits of regenerative amplification. The usual grid condenser 7 and grid leak 8 cause the device to also function as a detector.

The only reaction between the two tuned circuits, in this, case occurs when they are tuned alike. At this point the signal circuit finite impedance compared with the tuned circuits, and the coils not coupled, there would. be, no reaction between the circuits.

This desirable condition may be approached by making the tuned circuits of low impedance, i. e., large capacity and low inductance.

In the arrangement shown in Fig.2 a resonant circuit 9 which is tuned to the local frequency, is connected to the plate circuitand this resonant circuit is coupled to the coupling coil 10 in the grid circuit. In this case also oscillations may be produced with substantially no reaction between the two tuned circuits. The grid coil 10 should be of so few turns that its coupling with the tuned circuit 9v will, under no conditions, bring its impedance up to an appreciable value ascompared with the grid impedance.

It will also be found desirable when signal regeneration is employed as indicated in Fig. 2 to use ashunting resistance 11 across the plate tuned circuit for the following reason. At resonance the impedance of the multiple tuned circuit 9 in series with the plate becomes very high. The result will be a decrease in the signal frequency plate current as the oscillator setting approaches zero beats and a consequently reduced regeneration and a weakening of the signaling current. There will also be a reaction on the amount of signal regeneration by the shift in phase of the plate current as the plate tuning passes through the point of maximum impedance. These effects may be minimizedby making the plate tuningof lov impedance as compared'with the plate impedance, either by using a large capacity and small inductance or by including a portion only of the inductance in serie with the plate as indicated in Fig. 2. ,The use of the resistance 11 in shunt to the portion 12 of the inductance which is in series with the plate also decreases the reaction of the tuning on the plate current. The value of the resistance 11 may be aboutequal to the value of the plate impedance. A portion of the oscillator frequency plate energy will be wasted by this arrangement butthis will not be objectionable in this case. By means of the plate tuning-as shown in Fig. 2, the plate energy can be'used more 'efiiciently than with grid tuning and plate tickler coil as shown in Fig. 1. The oscillations inthis case can be maintained with small amplitude variations on the grid and therefore without choking the tube or reducing its sensitiveness to the signal.

In Fig. 3 I have shown a continuous wave amplifying and detecting system employing three tubes 13, 1 1 and 15. Tube 13 is connected as a regenerative amplifier and de tector. The audio frequency current produced in the plate circuit of tube 13 is supplied by transformer 16 to the grid circuit of tube 14. A tuned circuit 17 in the grid circuit of tube 1d is coupled by coupling 18 to the plate circuit to produce the local oscillations which are impressed by means of the coupling 19 upon the grid circuit of tube 13. Tube 14 thus acts as audio frequency amplifier and oscillator. The output from the plate circuit of tube letis supplied by the audio frequency transformer 20 to the grid circuit of tube 15 which thus acts as an audio frequency amplifier. The receiving telephones 21 are connected to the plate circuit of tube 15 inthe usual manner. Extra windings 22 and 23 may be supplied upon the transformers 16 and 20 connected to the jacks 2 1 and 25 to permit connecting the telephone receivers to the output circuits of tubes 13 and 141 if desired. The plate circuits of all of the tubes are supplied with current from a single source 26. The primary windings of transformers 16 and 20 are preferably shunted by by-pass condensers 27 to permit the passage of high frequency currents flowing in the plate circuits,

In Fig. 1 I have shown a slightly different three tube arrangement. In this case tube 29 serves as an oscillator to feed local oscillations to the grid circuit of tube 30, which acts as a detector, by means of the shielded connecting links 31. The transformer 32 in the plate circuit of tube supplies audio frequency currents to the grid circuit of tube 29 causing this tube to also act as audio frequency amplifier as well as oscillator. Audio frequency currents from the plate circuit of tube 29 are supplied by transformer 33 to the. grid circuit of tube 3&- and amplified audio frequency currents from the plate circuit of amplifier tube. 3fmay be supplied by transformer 35 and jack 36 to the receiving telephones. Tube 341- may also be used as a radio frequency amplifier by inserting the plug 87,which is connected to the antenna coupling. circuit 38 in the jack 39 which is connected in the grid circuit of tube 3 1. By means of the coupling 40 the-amplified high frequency currents from the plate circuit of tube 3% are supplied to the grid circuit of detector tube 30. Ajacl; 41 may also be provided in the grid circuit of detector 30 to permit of the impressing of the received signaling currents directly upon the grid circuit of the detector.

To prevent undesired reactions between the different stages of amplification series reactances 42 and shunt condensers 13 will preferably be employed in the plate supply circuit-s. A low pass filter A is also preferably inserted in the plate circuit of de tector tube 30.

The arrangement shown in Fig. is similar to that shown in Fig. i with the exception that means is provided in this case whereby tube 29 may serve both as radio frequency amplifier and audio frequency amplifier, the jack permitting of the impressing of the received signaling currents directly on the grid circuit of tube 29. Tube 34 may serve both as audio frequency amplifier and radio frequency amplifier as in Fig. f. In case the arrangement is to be employed for the reception of interrupted continuous waves, spark signals or radio telephony, the feed back connection 46 may be adjusted for regenerative amplification. If the system is to be employed for receiving continuous wave telegraphic signals, the tuning and feed back may be adjusted so that tube 30 serves as a self-heterodyne de tector.

Certain of the novel. features disclosed in Figs. 3, i and 5 of this application are described and claimed in my copending application, Serial No. 712,442, filed May 10, 1924.

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

1. The combination in a signal receiving system of an electron discharge device having plate and control circuits, two tuned circuits associated with said device, one of which is resonant to the signal frequency and the other to a slightly different frequency, an inductive feed back connection between plate and control circuits whereby oscillations of a slightly different frequency from the signal frequency may be produced and a second inductive feed back connection between plate and control circuits for producing regenerative amplification of the signaling current.

2. The combination in a signal receiving system of an electron discharge device having plate and control circuits, two tuned cir cuits connected in said control circuit, one of which is resonant to the signal frequency and the other to a slightly different frequency, a feed back connection between plate and control circuits whereby oscillations of a slightly different frequency from the signal frequency are produced in the control circuit, and a second inductive feed back connection between plate and control circuits for producing regenerative amplification of the signaling currents.

3. The combination in a signal receiving system of an electron discharge device having plate and control circuits, a tuned circuit connected to the control circuit which is resonant to the signal frequency, a second tuned circuit connected to the plate circuit which is resonant to a frequency slightly different from the signal frequency, a feed back connection from the plate circuit to the resonant circuit which is connected to the control circuit and an inductive feed back connection to the control circuit from the resonant circuit connected to the plate circuit.

4t. The combination in a signal receiving system of an electron discharge device having plate and control circuits, at tuned circuit connected to the control circuitwhich is resonant to the signal frequency, a second tuned circuit connected to the plate circuit which is resonant to a frequency slightly different from the signal frequency, a resistance in shunt to said second tuned circuit, a feed back connection from the plate circuit to the resonant circuit which is connected to the control circuit and a feed back connection to the control circuit from the resonant circuit connected to the plate circuit.

5. The combination in a signal receiving system of an electron discharge device having plate and control circuits, a tuned circuit connected to the control circuit which is resonant to the signal frequency, a second tuned circuit connected to the plate circuit which is resonant to a frequency slightly different from the signal frequency, and a resistance in series in the plate circuit and in shunt to a portion of the inductance of the second tuned circuit.

6. The combination in a signal receiving system of an electron discharge device having plate and control circuits, a tuned circuit connected to the control circuit which is resonant to the signal frequency, a second tuned current connected to the plate circuit which is resonant to a frequency slightly different from the signal frequency, and resistance of the same order of magnitude as the plate impedance in series in the plate circuit and in shunt to a portion of the iuductance of the second tuned circuit.

T. The combination in a signal receiving system of an electron discharge device having plate and control circuits, and two independent feed back connections between said circuits which are external to the electron discharge device, one of said feed back connections being adapted to produce oscillations of a radio frequency different from the signaling frequency, and the second of which is adapted to produce regenerative amplification of signaling currents and means for detecting beats produced by in teraction of the currents of two different frequencies.

8. The combination in a signal receiving system of an electron discharge device having plate and control circuits, two tuned circuits associated therewith which are resonant to the signal frequency and a radio frequency differing from the signal frequency,

and two independent feed back connections &

between said circuits Which are external to the electron discharge device. one of said feed back connections eing adapted to produce oscillations of a radio frequency diflerent from the signaling frequency and the second of which is adapted to produce rcgenerative amplification of signalii'ig currents and means for detecting heats produced by interaction of the currents of two different frequencies.

9. The combination in a signal receivingsystem of an. electron discharge device having plate and control circuits, :1 tuned circuit connected to the control circuit which is resonant to the signal frcquen'cy a' second circuit associated with the device which is resonant to a radio frequency differing from the signal frequency, and twoindependent feed back connections between said circuits which are external to the electron discharge device, one of said feed back connections being adapted to produce oscillations of a radio frequency different from the signaling frequency and the second of Which is adapted to produce regenerative amplification of signaling currents and means for detecting beats produced by interaction of the currents of two different frequencies.

In itness whereof, I have hereuto set my hand this 4th day of October, 1922.

EDlVARD W. KELLO GG.

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