US 1798415 A
Description (OCR text may contain errors)
Mamh 31, 1931. W. HAHNEMANN &
SIMULTANEOUS WIRELESS BROADCASTING Filed June 29, 1929 Patented Mar. 31, 1931 WALTER HAHNEMANN, OF BERLIN-MABIENFELDE, GERMANY, ASSIGNOR TO C. LORENZ AKTIENGESELLSCHAFT, OF BERLIN-TEMPELHOF, GERMANY SIMULTANEOUS WIRELESS BROADCASTING Application filed June 29, 1929, Serial No. 374,677, and in Germany June 9,
' Application filed in Germany June 9, 1928.
When supplying large districts with news by broadcasting in employing short and ultrashort waves difficulties are encountered in that owin to the peculiar physical properties of such short waves it is impossible to obtain a uniform distribution of the total energy emitted. As is known there will occur particularly with short waves alternating zones in which a reception ofsignals is almost impossible while in others the signals will arrive at an excellent magnitude of sound in the receiver. The location of said zones is dependent on the one hand on the time of the day and on the other hand on the wavelength employed. In the areas between the individual zones the receiving energy will drop to very low values, and in order to obtain in spite of this in a given district a sufficiently high power of sound in the receiving apparatus at every point, the sending station would be required to operate on exceedingly high energy. A sending station of this kind cannot be constructed in view of the present state of the art, and besides it would prove non-economical.
The method and device according to this invention avoids these drawbacks an it will broadcast from a central sending station one and the same news on diiierent wave lengths selected in such a manner that the sum of their zones of incidence will cover the total area to be supplied with the news.
In the drawing one mode of execution of the invention is shown by way of example.
Figure 1 illustrates diagrammatically the distribution of energy of the different waves in dependency on the distance from the sending station.
Figure 2 shows the distribution of news by means of dilferent waves, whose zones of incidence are so chosen that the total area concerned is covered, and
Figure 3 shows the arrangement of a sending apparatus for carrying out the method of broadcasting according to the invention.
If according to curve a of Figure l the receiving intensity of a sending apparatus working on the wave-length 1, is represented as a function of the distance of the receiving station from the sending station, for instance only one quarter of the total area will be furnished with sutllcient receiving energy. l-iccording to the invention, now three additional sending apparatus, whos wave-length is so chosen that the zones of the most favorable reception are located adjacent each other, are arranged at the central sending station. The receiving intensity of the individual sending apparatus is shown in the curves 5 tool of Figure 1 in correspondence with their different wave-lengths 24. If these four intensity curves are added it follows a uniform power of sound in the receiver for the total area to be covered. As the zones of incidence of the waves very accurately depend on the wavelength the illustrated distribution of intensity can be easily and accurately maintained.
The idea of the invention is again represented with respect to Figure 2 in order to clearly show the interlocking of the various zones. The sending station is designated by S while the different receiving zones are marked by different hatching.
It is more economical to arrange according to the invention several short wave sending stations operating on less energy at the central sending station successively and to employ them in unison for operating them like a sending station of higher capacity, which as stated above will meet with difficulties.
For carryingout the method according to the invention the arrangement of sending apparatus shown in Figure 3 diagrammaticall -may be used. Four aerial wires of the sending station are supplied through a sending apparatus 5, 6, 7, 8, which are actuated in common by a microphone 9. The aerial wire 1 will emit the wave A 1, the aerial 2 the wave A 2 and so on. The circuits of modulation for all four sending apparatus are connected in parallel by means of the wires 10 and 11, upon which is forced in common the modulation by means of the microphone and the interposition of an intensifying valve 12. The latter is equipped with an input transformer 13 while the output transformer 14 is of any desired design. It is pointed out'that the transmission apparatus 5'to'8 may be of any desired design, for the subject matter of invention it is only material to actuate all transmitting apparatus in unison, since all zones are to receive the same news.
According to a further feature of the invention a change of the wave length is offected each time according to respective daytime or there are arranged a few more sending apparatus at the central transmitting station respectively in order to supply all zones properly. At night for instance the first zone will'be displaced at a greater dis tance from the transmitting station than in daytime. For that reason it will become necessary to connect a 'few more transmitting apparatus at night, which will cover also the larger space formed between the transmitting station and the receiving zone in a corresponding manner. Just according to the importance of a news the latter might be supplied to a smaller or bigger audience, in that the number of the transmission waves is changed. The connection of the various aerial wires for transmission is effected by means of the connecting switches for the aerial wires designated 15, 16, 17, 18.
As the location of the Zone will not only depend on the wave length but also on the 7 angle of radiation at the transmitting station, it is further suggested, to alter it by means of suitable combinations of aerial Wires, admitting of different directing efiects in order to obtain an accurate observance of the individual zones. It will also be possible to compensate the difference in the radius of action in accordance with the time of the day by a corresponding change of the angle of radiation.
1. Arrangement for the simultaneous distribution of news throughout a given area by wireless broadcasting comprising in combi nation a central transmitting station having a plurality of transmitters for simultaneously transmitting the same news by means of short waves of different frequencies, said waves be ing so chosen that the sum of their zones of incidence will complementarily cover the total area to be supplied by such news.
2. Arrangement for simultaneous distribution of news throughout a given area by wirelessbroadcasting comprising in combination a transmitting station embodying a plurality of transmitters, each including an antenna, for transmitting simultaneously the same news by means of short waves of difierent frequencies so chosenthat the sum of their zones of. incidence will complementarily cover the total'area to be supplied with said news, and means for selectively connecting each receiver with or disconnecting it from its antenna for varying the number of waves to be transmitted at a given time to vary the proportional distribution during different hours of the day and night; 7
3., The method of reliable wireless transmission of news matter throughout a given area by the use of short Wavesof different 1 frequencies which comprises so selecting the use of short waves-of different frequencies which consists in so selecting the frequencies that the sum'of their zones of incidence will complementally cover the total area to be supplied by such news matter, transmitting such news matter from said central transmitting station simultaneously by means of short waves of different frequencies so selected, and varying the number of carrier waves transmitted in such manner as toeflect a substantially uniform distribution of the waves over the given area at different hours of the day and night.
- In testimony whereof I have aflixed my I signature.