US1734772A - Arrangement for wireless telegraphy and telephony - Google Patents

Description

Nov. 5, 1929.

w. MOSER ARRANGEMENT FOR WIRELESS TELEGRAPHY AND TELEPHONY lNVENTOR MOSEP.

ATTORNEY WILHEL Filed Dec. 1923 Patented Nov. 5, i929 WILHELM Mosnn, on BnnLIn, GERMANY, Assienon ro ensnL scI-mrr run 131mm.- LOSE TELEGRAPHIE M. B. H., on BERLIN, GERMANY, nconronnrronon GERMANY ARRANGEMENT non .WinELE-ss rnnne'nnri-ir 'inun' rntnrnoivv Application filed December 7, 1923, Serial No. 679,053, and. in Germany January 17, 1923.

In German Patent, No. 298,622, an arrangement adapted for wireless telephony and operating with continuous waves is shown in which a three-electrode tube is connected between two points of the antenna circuit for absorbing varying amounts of energy from the antenna in conformity 'ith the speech waves to be transmitted. Connections have also been proposed wherein the absorbing or control tube-is coupled either inductively or capacitively with the aerial. The use of an absorbing control tube is of particularly great advantage in combination with tubetransinitters. In transmission arrangements involving intermediate circuits, for instance, the control tube can be connected in parallel to a larger or smaller portion of the inductance of the intermediate circuit. In arrangements of this nature the control tube receives its anode potential from the high frequency potential of the intermediate circuit, and, by virtue of the rectifying action between the anode and cathode of the tube, a mean, direct current anode voltage is set up which has controlling influence upon the operation of the arrangement. For the production of useful speech, as is well known, it is important that the center of speech voltage fluctuations at the grid of the control tube shall lie on the straight portion of the characteristic curve, and above all, the working region of this characteristic, for the purpose of keeping the requisite grid speech energyat a low value, must fall within the range of negative grid potentials. For this object, the high frequency potential of the intermediate circuit is inadequate. Furthermore, in transmission arrangements without operator, as used, for instance in high frequency telephony along power lines, the high frequency potential may be subject to changes due to heating or coupling variations, with the consequence that the working point is shifted toan un favorable portion of the characteristic.

In accordance with the present invention, in order to obviate the said difficulties, there is applied to the anode of the control tube a direct current voltage which is so proportioned that the working current of the control tube is caused .to lie always within the region this direct current voltage is obtained from a source of'electrical energy separate from the generator of the transmitted current. At the same time, the constant permanent voltage of thegrid can be readily adjusted in a known man'ner'so that the center of speech voltage variations at the grid of the control tube falls within and preferably at the middle of the straight portion of the characteristic curve.

In the drawing,

' Fig. 1 is a diagrammatic representation of a circuit arrangement embodying the invention and in which voltage for the anode of the control tube is obtained from a direct current source separate from thedirect current source of the sending tube;

of negative grid potentials. Preferably, also,

Fig. 2 is a diagrammatic representation of a modified form of circuit arrangement also comprising a separate source of'voltage for the anode of the control tube and Figs. 3 and 4; illustrate a circuit arrangement of modified form in which auxiliary voltage for the anode of the control tube is obtained from the direct current source of the sending tube. g

In the illustrated arrangement, a transmitting tube 1 With anode direct current source 2 constitutes the generator of the transmitted current and operates upon intermediate circuit 3, for instance, in't-hreepoi'nt connection. Control tube 4, the filament of which may, for example, be heated in parallel with the filament of the transmitting tube, is connected through auxiliary battery 5 with the point 6 of the intermediate circuit 3, the positive pole of battery 5 being, of course, connected with the anode 7 of the control tube 4. Since battery 5 is very liable to possess an unduly large and" therefore harmful ground capacity, the invention is preferably embodied in a circuit arrangement, such as is shown in Fig. 2, in which the auxiliary battery 5 is blocked from the connecting line 67 for high frequency by choke coils 8,.Wll'll6 for the high' frequency a connection is created from 6 to 7 by way of a condenser 9. The condenser 12 serves to couple the tube 1 to the circuit '3 and yet permits of the anode potentials of tubes 1 and 4 being independent of one another.

'12 and 18, isolate as alternating current circuits the right-hand circuits of the figure, while the circuits toward the left serve to place upon the anodes a desired fixed potential. I

In many cases, especially where the control and transmitting tubes have like characteristics such potentiometer connection can be dispensed with and the auxiliary anode potential of the control tube obtained directly from the direct current source 2 of the tube 1, as depicted in Fig. In this case the con. t-rol tube 4; acts simultaneously in parallel relation with the transmitting tube, thereby causing variations in the anode voltage of the transmitting tube in the well-known man- 1 nor, assuming that the anode direct current source 2 is able to supply only a limited power. This auxiliary modulation I shall term indirect modulation, in contradistinction to the type of modulation occurring in Figures 1, 2, and 3, that is, modulation by direct application of the modulating energy to the high frequency alternations in the os cillatory output circuit, whichI shall call direct modulation. Indirectmodulation constitutes a reinforcement of the direct modulation control hereinbefore described since, for instance, in case of increased current consumption of the control tube, energy is derived from the intermediate circuit, on the one hand, while, on the other hand, the anode voltage of the transmitting tube is simultaneously decreased with the consequence that thetransmitted energy is still further diminished. To intensify this effect, an inductance coil or current impeding device 11 may be inserted in the anode direct current supply lead in the well known manner, as shown diagrammatically in Fig. 4.

.Having described my invention, what I claim is:

1. In combination, an oscillator tube connected to a resonant circuit, a modulator tube the output of which is connected across the resonant cir uit as a parallel radio frequency path for direct modulation, and a source of relatively constant currentv for the parallel connected anode circuits of the tubes to obtain indirect modulation.

2. In combinatioman oscillator tube connected to a resonant circuit, a modulator tube the output of which is connected across the resonant circuit as a parallel radio frequency circuit, a source of potential for the anodes of the tube, radio frequency choke coils connected between the anodes and said source,

and an audio frequency current impeding device in series with said source and the tube anodes to obtain indirect modulation.

l. In combination, an oscillator co1nprising an electron tube and a resonant circuit arranged in three point connection, a potential supply circuit connected to the anode circuit of said tube, a modulator tube the input circuit of which is coupled to a source of modulating energy, while the output circuit is connected across the resonant circuit for direct modulation, another potential supply circuit connected to the anode ofthe modulator tube, and means including a blocking condenser for connecting together the anodes of said tubes.

5. The combination with an oscillator C0111- prising an electron tube, a source of direct anode potential, and a resonant circuit, of means to modulate the alternating energy of the oscillator by both directly modulating the alternating energy in the resonant circuit and simultaneously varying the potential of the anode of the electron tube.

6. The combination with an oscillator comprising an electron tube, a source of direct anode current, and a resonant circuit, of means to modulate the output of the oscillator by both direct modulation of the alternating energy in the resonant circuit, and indirect modulation by variation of the direct current supplied to the anode of the electron tube.

7. In combination, an oscillator tube connected to a resonant circuit, a modulator tube the output of which is connected across theresonant circuit as a parallel radio frequency path for direct modulation, a source of potential connected to the anodes of the tubes in parallel, means for individually and relatively varying the potentials placed on said anodes and a modulation frequency current impeding device in series with said source and the tube anodes to obtain indirect modulation. 7

DR. WILHELM MOSER.

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