US1427832A - Radiotelephony - Google Patents

Description

F. S. McCULLOUGH RADIOTEL'EPHONY.

.APP-LICATION FILED JULY 7.19m.

Lqzmgsz, PatentedSept. 5, 1922'.-

2 SHEETS-SHEET 1.

F. S., Mc'CULLOUGH.

RADIOTELEPHONY.

APPLICATION FILED JULY 7,1919.

m mm m A 5 E4; 4 0 P W W 1h 7 A m m J Patented Sept. 5, 1922.

UNITED STATES PATENT OFFICE.

FREDERICK S. McCULLOfiGH, OF CLEVELAND, OHIO, ASSIGNOR T0 GLENN L. MARTIN,

OF CLEVELAND, OHIO.

BADIOTELEPHONY.

Application med July 7, 1919. Serial No. 308,977.

To all W/umi. it may concern:

Be it known that I, FREDERICK S. MoCUL- LoUon, a citizen of the United States, resident of Cleveland, county of Cuyahoga, and State of Ohio, have invented new and useful Improvements in Badiotelephony, of which the following is a specification, the principle of the invention being herein explained and the best mode in which I have contemplated applying that principle, so as to distinguish it from other inventions.

My invention relates to systems of radio telephony and telegraphy, and, more particularly, to systems for transmitting speech by means of radiant energy, although it may also be applied to other purposes.

The object of my invention is to provide uniform and regular electric oscillations with small damping and having abundant power, and moreover, to furnish these oscillations by means of a simple, compact, economical and continuously reliable apparatus which operates with freedom from inherent vibrations of audible frequency, and is therefore especially applicable to radio telephony, although it may also be used for any other form of radio transmission.

Among the means hitherto employedto supply undamped oscillations for radio telephony, are high-frequency spark gaps and vacuum tubes. Considerable amounts of power can be employed with the spark gaps, but the oscillations produced are irregular, and introduce noises and sounds which interfere very greatly with satisfactory speech. The vacuum tubes produce smooth and regular oscillations, but are limited in power. Higlrtrequency alternating-current machines are also used to produce oscillations for radio work, but are unsuitable where space and weight must be limited.

The present invention provides a means to make use of the spark gap, and at the same time to eliminate its objectionable features. The means I employ is an are contained in a sealed tube filled with an inert gas, such as argon, but is not limited to any particular gas. This are is placed in series with'the high-frequency spark gap and acts as a stabilizer or filter or buifer or equalizer for the irregular oscillations emanating from the spark gap. In this way high-frequency oscillations of great power and yet of smooth and regular form are produced, and can be used for any kind of radio transmisslon.

This system is particularly applicable to radio telephony, and for such purposes it possesses an additional feature which is of great value in modulating the power current by means of the sound waves. This additional feature consists of a third electrode in the tube containing the are, placed in the path of the are, between the anode and the cathode, and in circuit with the microphone transmitter and battery.

Other advantages of my invention will appear from the further description, reference being made to the drawings accompanying this specification.

The annexed drawings and the following description set forth in detail certain means embodying my invention, the disclosed means, however, constituting but one of the various mechanical forms in which the principle of the invention may be applied.

In said annexed drawings:

Figure 1 is a diagrammatic representation, showing one arrangement of my circuits and a View of one form of my arc st abilizer.

Figure 2 is a diagram of another arrangement of circuits with a modified form of my stabilizing are having a third electrode.

Figure 3 shows a third arrangement of circuits and a third form of my stabilizing arc, the third electrode being in the form of a filament.

Figure 4; shows a fourth arrangement of circuits, with the same form of stabilizing are as shown in Figure 3.

In Figure 1, 1 is a generator; 2, 2, are impedances; 3 is a variable resistance; 4 is a condenser; 5 is a high-frequency spark gap; 6 is a sealedvessel containing an inert gas, an anode 7 and a cathode 8, between which my stabilizing are is formed; and 18 is a variable condenser. 1 9 is the primary of an oscillation transformer, the secondary of which, 10, is a variable inductance, in circuit with the antenna 11, the ammeter 12 and the ground 13. 14 is a microphone for impressing modulations of audible frequency on the antenna circuit. 16 is a switch for shortcircuiting the microphone when it is desired to send telegraph signals by means of the key 15. 17 is a switch which is closed when the microphone is used, and open when the key 15 is being operated.

In Figure 2, 1 is a generator, 2, 2 are impedances, 3 is a variable resistance, 4 is a condenser, 5 is a highrfrequency spark (gap, 6 is a sealed vessel, in which are an ano e 7 a cathode 8, and a third electrode 20; the anode and cathode being in the power circuit with the spark gap, and the third, electrode being in the modulating circuit with the microphone. 9 is the primary of an oscillation transformer, the secondary of which, 10, is in circuit with the antenna 11, the ammeter 12, and the ground 13. 14 is a microphone; 15 is a telegraph key; 16 is a switch for shortcir'cuitingthe microphone; 18 is a variable condenser about the stabilizing arc inthe sealed vessel 6; 19 is a variable condenser. 21 is an inductance coil in circuit with the microphone and the electrode 20, and in inductive relation to the secondary, 10, of the oscillation transformer, and 22-is a battery in the modulating circuit.

In Figure 3, 1 is a generator; 2 is an impedance; 3 is a variable resistance; 4 is a condenser; 5 is a spark gap; 6 is a sealed vessel containing an anode 7, a cathode 8, and a third electrode 23 in the form of a filament which can be heated by an external source; 9 is the primary of an oscillation transformer, the secondary of which, 10, is in circuit with the antenna 11, the ammeter 12 and the ground 13. 14 is a microphone; 15 is a telegraph key; 16 is a switch for shortcircuiting the microphone; 19 is a condenser in the modulating circuit which contains the microphone and the filament 23. 24- is a battery which is used for heating the filament and which also may supply current for the modulating circuit. 25 is a variable resistance for regulating the heating current through the filament, and 26 is a potentiometer resistance for adjusting the potential offilament 23 with respect to the oathode 8, thus regulating the current in the modulating circuit. The variable resistance 26 has a resistance of several thousand ohms, so that very little of the current from the battery 24 passes through it, and its principal function is that of a potentiometer. 27 is aswitch and 28 and 29 are contacts. When the microphone is in use, the switch should be in the position as shown, making contact with 28. When the telegraph key 15 is to be used, however, the switch should be thrown so as to make cont-act with 29. 30 is a variable condenser about the sealed vessel 6 and the coil 9.

In Figure 4, 1 is a generator, 2 is an impedance, 3 is a variable resistance; 4 is a condenser; 35 is a spark gap of any suitable kind; 6 is a sealed vessel having an anode 7, a cathode 8, and a third electrode 23 in the form of a filament. 9 is the primary of an oscillation transformer, the secondary of which, 10, is in circuit with the antenna 11, the ammeter 12 and the ground 13. 15 is a telegraph key; 17 is a switch which is closed when the key is not in operation, and open.

when it is desired to send telegraph signals. 2 1 is a battery; 25 is a variable resistance. 27 is a switch having contacts 28 and 29. 30 is a variable condenser about the sealed vessel 6, 31 is a battery in the modulating circuit; 32 is a microphone; 33 is a microphone battery, and 34 is a transformer.

As shown in the drawings, the power circuit comprises the generator, the spark gap and the stabilizing arc, together with other features. The generator 1 is of relatively high voltage; the current from this generator is controlled by the impedances 2 and the resistance 3 and charges the condenser 4:, which discharges across the spark gap 5. This gap may be of any suitable kind, as shown in Figure 4:, but ispreferably composed of dissimilar metals of such a character and so disposed that when the apparatus is active, a much larger discharge current passes across the gap in one direction than in the opposite direction, as shown in the other figures. I have employed metals such as copper and aluminum, and other metals which will also be effective have been used, or a mixture of alloys of two metals will also produce similar effects.

IVhen this gap operates by itself, as in previous systems, it produces oscillations of high frequency. but of more or less irregularity, as can be easily observed by listening in with an appropriate receiving device, when there are heard hissing and scratching noises often loud enough to obliterate articulate speech. In order to overcome this difficulty, I invented and developed my arc stabilizer modulating tube. This tube contains electrodes composed of dissimilar metals. The cathode. for instance. is of tungsten, and it has been found most advantageous to use it in the shape of a coil. The anode is preferably composed of a disk of graphite. In the preferred form of my invention, there is also placed between the anode and the cathode, a third electrode, preferably composed of tungsten, which acts as-the controlling member of the modulating circuit.

In preparing the tube, the space within it should be carefully evacuated of all gases and vapor, and particular care should be taken to remove electro-negative gases, or gases which will, at high temperatures, yield electro-negative gases. for example, water vapor. After the tube is carefully evacuated, it is then filled with an inert gas, such as argon, although it is not limited to any particular gas.

The operation of this are within the sealed vessel is probably as follows: When the discharge takes place across the gap 5, the initial resistance of the tube 6 is broken down, a flow of current takes place through the tube, and an arc is established between the'electrodes. The effect produced by this are tabilizer modulating tube is such that the spark-gap oscillations, which were previously of a varying amplitude, are now regulated so that they are of constant amplitude and smooth form, and all disturbing noises are eliminated. This arc stabilizer tube can carry heavy currents and is generally designed for comparatively low voltages. I have operated it with currents of eight (8) amperes, at thirty-five volts, but I do not limit myself to any particular currents or voltages.

I/Vhen voice modulations are impressed upon the power circuit, therefore, thereis no interference with the speech vibrations. A condenser may be shunted across the anode and cathode of the tube, to increase the current in thepower circuit.

In Figure 1, the voice modulations are impressed upon the antenna circuit by a microphone, and there is also connected with this circuit a telegraph key, by means of which signals can be sent. In the preferred forms of my invention, shown in the other figures, the voice modulations and the telegraph signals are impressed upon the power circuit by means of a control member which consists of a third'electrode in the sealed tube or vessel, placed between the anode and the cathode of the arc. The potential of the control member or element is preferably 'made negative with respect to. the cathode element, so that when the microphone is spoken into, the current in the power circuit drops to zero, which produces exceptionally good articulation. The control member may be charged negatively by a battery such as shown at 22, Figure 2.

The oscillation transformer 9, 10, for transferring the oscillations of the power circuit to the antenna circuit, comprises a primary, 9, loosely coupled to the secondary, 10. In the form of my system shown in Figure 2, the coil, 21, in the controlling or modulating circuit is wound tightly upon the secondary of the oscillation transformer, providing a loose coupling to the secondary 10. This arrangement enables me to increase the spark frequency in the power circuit. But this auxiliary coil may be dispensed with in some forms of my system.

In Figure 2, the control member, 20, is shown as an electrode in the sealed vessel, and it may have any suitable form, such, for instance, as a wire wound in a flat spiral. I find that under some circumstances, I am able to improve the operation of my system,

In forms of my system where the third electrode is not preheated, I sometimes preheat the cathode by making it inthe form of a filament and heating it by a source external to the tube, such as a battery. This preheating of the cathode assists in starting the are quickly, and has other advantages.

I have found that by inserting my arc stabilizer tube, the efficiency of the system is greatly increased. For example, without the tube, the current in the power circuit is three and one-half (3J amperes, and the current in the antenna circuit isone and onehalf (1%) amperes. On inserting the tube, the current in the power circuit drops to about three (3) amperes, while the current in the antenna circuit rises to two and one half (29;) amperes. This improvement is probably due to the increased smoothness and regularity of the oscillations and their uniform amplitude owing to the action of the stabilizing arc.

I do not confine myself to the exact constructions and arrangements herein described, but may also employ other means well known to those skilled in the art, but what I claim and desire to secure by Letters Patent is:

1. In a system of radio telephony, a power circuit including a high-frequency spark gap and an electric are having an anode and a cathode, and a modulating circuit including a microphone and a third electrode associated with said are, said third electrode consisting ofa filament heated by a source external to the arc.

'2. In a system of radio transmission, a power circuit including a spark gap, an electric arc and an inductance coil, an antenna circuit including an inductance coil in mductive relation to said inductance coil in the power circuit, and a modulating circuit including a microphone transmitter and an inductance coil in inductive relation to said inductance coil in the antenna circuit. I

Signed by me, this 26th day of June, 1919.

F, S. MQCULLOUGH.

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