US 1805918 A
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May 19, 1931. A. MEISSNER OSCILLATION GENERATION.
Filed Oct. 20. 1928 gig m VIE??? LI F INVENTOR AL XANDE MEISSNER BY AQNEY waves.
patented May 19, 193i UNETED STATES ALEXANDER MEISSNER, OF BERLIN, GERMANY, 'ASSIGNORTO TELEFUNKEN GES ELL- 7 PATENT OFFICE SCI-IAFT FUR DRAHTLOSE TELEGRAPHIE M. B. H. HALLESCHES, OF BERLIN, GER- MANY, A CORPORATION OF GERMANY oscILLArron GENERATION Application. filed October 20, 1928, Serial No.
This invention relates to the generation of oscillations, and more particularly to the generation, alternately, of oscillations of different frequencies, for the reduction of fading.
The object of the present invention is to provide a transmitter arrangement for wireless communication especially on extra-short It is a well-known fact that when working with short waves disturbances in traflic are often produced because the income ing signal strength becomes periodically or transiently very small or even drops to zero. Such variationsv in intensity, known as fading, are substantially due to interference phenomena. In order to eliminate them it is suggested to send the same signals simultaneously on carriers of two or more frequencies, inasmuch as fading depends upon the frequency that is used, so that, if two or more different wave-lengths are employed, simultanenous extinction of both or all of these frequencies is not to be anticipated.
Now, in order that it may be feasible to receive signals sent out on, say, two waves, with one receiver, and to economizein the use of available signalling frequencies, it is a. preferable plan to utilize two frequencies which are but slightly different from each other. At the transmission end the generation of such closely adjacent frequencies gives rise to the difficulty that the two transmitters are subject to marked mutual interference, so that the oscillations of one of these transmitters, under certain circumstances, may be .entrained by or fall inside the range of forced oscillations of the respective other transmitter tube, with the result that, instead of the intended two frequencies, only one frequency is sent out.
In order to overcome these practical difliculties, according to the disclosure of the present invention, the two thermionic tubes provided to generate or amplify the different frequencies are supplied from an alternating current source in push pull or phase opposition, so that the plates of the two transmitters are alternately fed with the positive halfcycles required for the production of oscillations. In this way, all chances of one of the tubes happening to fall inside the range of 313,703, and in Germany November 24, 1927.
not to speak of the fact that the use of sucha 1 working potential offers this further merit that the working potential changes inside a half-wave in its intensity whereby a modulation of the radio frequency sent is caused. Radio frequency waves modulated by alternating current, as has been found by tests, are subject to less fading, seeing that the modula-.. tion itself produces a decomposition or division of the frequency.
The specification is accompanied by ings, in which d Figure 1 is awiring diagram for one form of my invention; and p I v Figure 2 is a modification in which the frequency change is obtained in amplifier stages.
An arrangement according to this invention which may be regarded as an embodiment of the idea chosen by way of example is illustrated in the accompanying drawings. Two thermionic tubes E1 and E2 are connected transmitter fashion and are made to work upon two antennae A1 and A2. One of these thermionic tubes, E1, contains in its plate circuit an oscillation circuit S1, and in its grid circuit an oscillation circuit 81, which are tuned to one of the waves, while the other thermionic tube has two similar oscillatory circuits S2 and 82 which are tuned to the other wave to be generated. The working potentials for these two tubes are furnished y way of transformer T from an alternating current source, as shown. The ends of the secondary winding T of said transformer are united with the two plates, while the middle point of the transformer isassociated with the two filaments. To shut off the alternating current operating current from the oscillation circuits carrying the radio frequency currents, blocking condensers K are provided.
It will be understood that, within the spirit of this invention, various other circuit arrangements arefeasible. For instance, arrangements could be made also so that the two thermionic tubes whose plates are supplied with alternating current potentials in phase opposition, are separately controlled. In this case, the tubes themselves do not act as generators, but as amplifiers,
Such an arrangement is indicated in Figure 2, which is quite similar to the arrangement shown in Figure 1 except that in this case the tubes E1 and E2 are amplifier tubes, rather than oscillator tubes. The energies of different frequencies are first generated in master oscillators M1 and M2, and these are separately fed to the tuned input circuits of the amplifiers. It will be noticed that in this case the output circuits S1 and S2 are both amplifiers which have been shown coupled to a single antenna A instead of two separate antennas, but, of course, this feature is applicable to either arrangement,
A transmission system for reducing the effect of fading comprising a first master oscillator for generating a first frequency, a first space discharge device amplifier circuit having input and ouput circuits tuned to said first frequency adapted to amplify the oscillations generated from said first oscillator, a second master oscillator for generating a second frequency, a second space discharge device amplifier circuit having input and output circuits tuned to said second frequency adapted to amplify the oscillations generated from said first oscillator, an alternating current source coupled in push-pull to the output circuits of said space discharge device amplifiers so that said amplifiers are made operative alternately, and means to radiate the resulting energy from both said amplifiers.