US2207571A - Transmitter keying system - Google Patents

Description

u y 1940- F. D. ANDREWS 2,207,571

TRANSMITTER KEYING SYSTEM Filed Sept. 15, 1958 Inventor Paul D. Andrews,

H is Attorney.

- Patented J ly.

UNITEDESTATE-ST azou'u PA ENT"lorries-ff TRANSMITTER xnrmc stem! I Paul nrnndrews, Schenectady, N. rte-amm- General Electric Companm'a corporation of r New York pp i n S p m 13,1938, Serial N6; 229,730 I P: c ams.- (c1. lacce 2' My invention relates .to"keying systems for radio transmitters or the=1ike,- and particularly to keying systems for' transmitters wherein-a space discharge device or tube is employed" as "a-keying, tube connected in series with the output circuit-of a second space discharge .device such as an amplifier.

It is an. object of the present invention. to provide an improved keying system requiring only a small number of .parts'to beadded to existing transmitter structures.

It is a further object to utilize, in, providing:

a keying system for, a transmitter, potential sources already present in the transmitter, such as rectiflers for supplyingamplifier anode potential "and grid-bias potential, as a potential source for the operation of the keying system.

' It is a particular objectfto provide improved means forobtaining in any desired circuit, such as a circuit including a keying tube, a potential which may 'be readily changed with respect to a potential reference point or to ground, for example from a negative to a positive potential. I The novel features which are considered .to

be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organivzation and method ofoperation together with further objects and advantages thereof may best be understood by reference to the followingide scription taken in connection with theaccom panying drawing the single figure whereof i1- lustrates diagrammatically a t'ransmittersystem' embodying my invention. 1

In the single figure of the drawing the numeral I designates a space discharge device having a cathode 2, an anode 3, and control electrode 4, and which-in the present embodiment'of the invention is an intermediate power amplifier of a radio transmitter. Any suitable means (not shown) may be employed to-neutralize feedback of energy between the anode and control elec trode circuits; The input and output circuits of v the amplifier are connected-"respectively to means (not shown) for producing, desired signals to be modulated by a keying means andfor radiating the modulated signals. As, these signal producing and radiating means form no partof the present invention they will not be described further herein. j

Potential for the anode-cathode circuit of discharge device I isprovided by a. rectifier apparatusi having a potentiometer resistor 6 c'onnected across itsloutput circuit .1 the low' potential; ornegative end 8 'of which is-at ground.

sliding contact 26'.

' The anode S ot; device I .is connected to a point of resistor 8 of suitable potential through a lead 9. Bias potential for the control elec trod e-" cathodecircuit of device I is slmilarlyprovided by a rectifier apparatus I Iihavirrg a potentiom eter resistor II connectedacross its output circuit I2 the end I3 (if-which having the higher,

or pbsitive, potential is at ground. 'The control electrode of device I is-connected to -apoint of resistorgll' of desired potential through a lead I4. I

To provide in series with the anode-cathode circuit of dischargedevice I an impedance which 'm'ay be varied-bye. keying 'meansto be described hereinafter, a space discharge device I5, or keying;tube, having an anode, I8, a cathode I1 and a control electrode I8 is connected between the nected, preferably .adjustablyas by a slidingcon- ..tact 2| .or other suitablemeans, to a point of "anydesired potential of resistor fi, and the other terminal 22 of which is,similarly,'preferably adjustably connected as by a sliding contact-23 to a point of any desired potential of resistor I I. The controlelectrode-cathode circuit of discharge device I5 is 'connected'to the resistor I9, the control electrode I8 being adapted to be connected to any desired point of "resistor I9, preferably adjustably, by a 'means such as a sliding contact 24. To varythe bias potential impressed onelectrode- I8 in accordance with a keying code a keying device 25 is interposed between ground and resistor IS, the device 25 being adapted mm preferably connected adjustably to the latter resistorb'y eans, for. example,'of a The anode potential supply source, comprising rectifier 5 shunted bypotentiometer resistor 6, and the bias .potential'supply source, comprising I rectifier ,IO shunted. by-potentiom'eter resistor II, together constitute for the resistor I9-a single source of potential, thetwo sections of thesingle source being connected respectively to the opposite terminals 20 and 22 of resistor I9. The potential range thus provided-for resistor I9 'exten'ds from' a point ofgreatest positive .po-

tential, which is terminal 21 of the first section, to an intermediate, or section, connection point indicated by numerals 8 or l3, which are respectively the points of lowest and highest potential of the first and second sections, and from this intermediate point to a point of greatest negative potential which is terminal 28 of the sec and section. In the present embodiment the intermediate point is at ground. Suitable filter means (not shown) for the out put circuits of rectiflers 5 and II! are preferably provided which may comprise, for example, usual choke coils in series in the output circuits and capacitors in shunt with the potentiometers.

Since terminal 28 of resistor I9 is connected to the resistor 6 which is at positive potential and terminal 22 is connected to the resistor II which is at negative potential, therefore at some point between the positive terminal 28 and the negative terminal 22 of resistor I9 the potential is the same as the potential of the intermediate or ground point, indicated by 8 or I8. The position of this floating ground" point on resistor I9 is determined in accordance with the adjustment of the points of connection of terminals 20 and 22, of resistor I9, along the potentiometer resistors Sand II. The arrangement of the single potential source and resistor I9 is thus such that for any given setting of the adjustment means 2 I and 23 four resistances comprised in the resistors 8, II and I8 are in a Wheatstone bridge circuit. The four resistance arms of the bridge are respectively 11 between positive p0 tential. point 2I of resistor 6 and ground, 1': be-' tween ground and negative potential point 28 of resistor II, 1': between positive potential point 2| and the floating ground point of resistor I9 indicated for the illustrated particular adjustment by the numeral 29, and 11 between the assumed floating ground point 28 and negative potential point 23 of resistor II.

Any point of resistor I8 between the positive end 28 thereof and the floating ground" point, or point of equalpotential with that of the connection point between the two sections of the single source, is at a potential positive with respect to the connection point (B or I8)' of the sections and any point of resistor I8 between the negative end 22 thereof and the floating ground .point is at a potential negative with respect to the section connection point. If, however, a conductive connection is made between the section connection point (8 or I3) and a point of resistor I9 other than the floating ground point, the potential of all points of resistor IS with respect to the section connection described embodying my invention, anode potential and bias potential are impressed on the anode 3 and control electrode 4 respectively of discharge device or amplifier tube I from the rectifiers 5 and III, and the input circuit of the discharge device I is energized by signal potential. The control electrode circuit of the keying tube I8. is connected to the resistor I8 in such manner, as illustrated at point 24, that when key 28 is in its illustrated open position the potential of the control electrode II of the tube I8 is negative with respect to the grounded, intermediate, or connection, point (8 or I8),and to the grounded cathode I I of this tube. Therefore, during the open condition of key 25 the keying tube I8 interposes a high impedance in series with the anode-cathode circuit of amplifier tube I suflicient to block the latter tube and to prevent the transmission of the signal to the antenna. Further, the key 28 is connected, as illustrated, to-

such point 28 of resistor I8 with respect to the connection point 24 0,! control electrode I8 that when the key is in closed position, thereby connecting the key connection point 26 of resistor I8 to the grounded intermediate or section connection point (8 or I3), the negative bias potential impressed on electrode I8 is removed and the bias potential becomes positive with respect to cathode I! of keying tube I5. Therefore, under the closed condition of key 25 the keying tube becomes conducting, thereby interposing only a lower negligible impedance in series with the anode-cathode circuit of amplifier tube I, which accordingly transmits the signal to.the antenna, j

or following amplifier tube, as the case may be;

Keying of the transmitter is, therefore, accomplished by alternately opening and closing the ground connection 28 of resistor I8 by means of the key 25.

My invention has been described herein in a particular embodiment for purposes of illustration. It is to be understood, however, that the invention is susceptible of various changes and modifications and that by the appended claims I intend to cover any such modifications as fall within the true spirit and scope of my invention.

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

1. In combination, a space discharge device having a cathode and a control electrode, a potential source, a resistance connected across two points of diflerent potential of said source; means to connect said cathode to a point of said source having a potential intermediate the potentials .of said two points, means to connect said control electrode to a predetermined point of said resistance, and means subsequently to connect said point of intermediate potential to a point of said resistance which is initially of different potential from that of said point of intermediate potential thereby to vary the potential of said predetermined point with reference to the potential of said point of intermediate potential.

2. In combination, a space discharge device having a cathode and a control electrode, a source of potential, a resistance connected across two points of different potential of said source, means to connect said cathode to a point of said source having a potential intermediate the potentials of said two points, means to connect said control electrode to a point of said resistance which is initially of lower potential than that of said point of intermediate'potential and means subsequently to connect said point of intermediate potential to a point of said resistance which is initially of lower potential than that of said point of connection of said control electrode to said resistance thereby to render the potential of said last-named point of said resistance positive with reference to the potential of said point of intermediate potential.

3. In combination, a space discharge device having a cathode and a control electrode, a source of potential, a resistance connected across points of said source which are respectively of higher and lower potential than an intermediate point of said source, means to connect said cathode to said intermediate point means to connect said control electrode-to a point of .said resistance which is initially at a lower potential than that of said intermediate point whereby a potential negative with respect to said intermediate point is impressed on said control electrode, and means subsequently to connect said intermediate point to a point of said resistance which is at least as close to the point of lowest potential of said resistance as said point "of connection of said control electrode to said resistance whereby said negative potential is removed electrode.

4. In combination, a space discharge device having a cathode and a control electrode, a potential source having two sections, means to connect said cathode to the high potential end of,

one of said sections and to the low potential end of the other section, a resistanceconnected between a point of predetermined potential of one of said sections and a point of predetermined potential of the other of said sections, means to connect said control electrode to a predetermined point of said resistance whereby a predetermined initial potential is impressed on said control electrode, and means subsequently to connect said cathode to a point of said resistance which is initially of difierent potential from that of said cathode whereby the potential impressed on said ll control electrode is changed.

connect the opposite terminals of said resistance respectively to said anode potential source and said bias potential source at points thereof respectively of higher and lower potential than that of the point oi connection of said cathode of said second discharge device to said sources, means to connect said control electrode to a predetermined point of said resistance whereby an initial bias voltage is impressed on said control electrode, and means to connect a predetermined point of said resistance to said point of connection of said cathode of said second discharge device to said from said control control electrode.

sources whereby abias voltage different from said initial bias voltage is impressed on said control electrode.

6. In combination, a space discharge device, a source of anode potential'and a source of bias potential for said device, two resistances connected respectively across said potential sources, a second space discharge device having its anodecathode circuit connected in series with the anode-cathode circuit of said first-named discharge device and said anode potential source, said second discharge device having a control electrode, a keying device, means to connect the cathode of said second discharge device to the low potential end of the anode potential resistance and to the high potential end of the bias potential resistance, a third resistance connected at the respective ends thereof to predetermined points of said first and second-named resistances, means to connect said control electrode to a predetermined point of said last-named resistance whereby a predetermined initial bias voltage is impressed on said control electrode, and means including said keying device subsequently to connect a predetermined point of said last-named resistance to said low potential end of said anode potential resistance, said high potential end of said bias potential resistance, and said cathode of said second discharge device whereby a'bias voltage different from said initial bias voltage is impressed on said control electrode.

7. In combination, a space discharge device, sources respectively of anode potential and bias potential forsaid device, two resistances connected respectively across said sources, a second space discharge device connected in series with. the anode-cathode circuit of said first-named disharge device and said anode potential source and having a cathode and a control electrode. means to ground said cathode, means to ground the low-potential end of theresistance connected across said .anode potential source. means to.

ground, the high-potential end of the resistance connected across saidxbias potential source, a

third resistance connected at the respective ends electrode, and means subsequently to ground a point of-said third resistance which is at least as close as said last-named point to the lowpotential end of said third resistance whereby saidnegative bias potential is removed'from said PAUL n. mnnnws.

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