US2086961A - Method for the wireless transmission of sound films - Google Patents

Description

July 13, 1937. K. vscHLEslNGl-:R 2,086,961

u METHOD FOR THE WIRELESS TRANSMISSION OF SOUND FILMS Filed Mamh e, 1954 Alix/IVG DIY/CE /ALRA/#ED/NTE FREQUENCY ,MAGE an/72x05.

L Fl E 10 FREQuE/vcy 4mm /f/f/z 1 :l: 16 l A 25 m 7 BRAD/v Tues IMAGE CONTE 15 LOW FHEGU/VCY SOUND HMFL/F/ER Patented July 13, 1937 PATENT OFFICE METHOD FOR 'EI-IE WIRELESS TRANSMIS- SION O-F SOUND FILMS Kurt Schlesinger, Berlin, Germany Application March 6, 1934, Serial No. 714,304 In Germany March 11, 1933 3 Claims.

It has been proposed to wirelessly transmit Visible occurrences andthe accompanying sound, e. g. sound. lms by the use of one single carrier wave. This method, however, owing to the, con- 5 Vditions associated with the width of band, can

onlybe employed with diiculty for the production of v13G-line images.

Upon making use of the superheterodyne principle in the receiving apparatus it has been found l to be desirable to operate with an intermediate frequency wave possessing in `each case a definite frequency, for example twice or three times the amount of the maximumimage frequency (in the case, therefore, of a 18o-line image with a maximum frequency of 54()Y k. c., approximately 1080 or 1620 k. c. or an intermediate value). Now it is extremely diflicult to adjust at the receiver the oscillator frequency necessary for generating this intermediate frequency. 20 An additional disadvantage of the methods hitherto known consists in the fact that-owing to the possibility oi double adjustment occurring in connection with superheterodyne receptionmerely a comparatively small utilization is possi bleof the frequency band available. Y

The method now disclosed enables these dis advantages to be avoided. According to the invention the new method of transmitting television images Aconsists in transmitting two completely independent, preferably ultra-short waves for` transmitting the contents of the image and ofthe accompanying sound with the characteristic feature of a reception method'according to the superheterodyne principle operating with 35 an oscillator device common for both said carrier waves, the frequency of said oscillator being adjusted to have a frequency between said ultra short wave carrying said image indications and Asaidrespective frequency carrying said sound indications for the purpose of obtaining the predetermined intermediate frequencies for the image and sound modulations respectively. According to the invention, the same local o-scillator is employed for theimage receiver and the sound receiver. In this connection the spacing of the sound-modulated ultra-short wave from the image-modulated ultra-short wave is so chosen that with correct adjustment of the sound receiver for obtaining the best reproduction of sound (which receiver is adjusted permanently to a preferably long, say, 200G-metre wave) eX- actly the best intermediate frequency Aresults in the image receiver.

If, for example, it is desired to employ in the image receiver anintermediate frequency of 200 metres and in the sound receiver an intermediate frequency of 2000 metres, there is employed for transmission of the sound an ultra-short' Wave, the spacing of which from the image short-wave amounts to 1650 k. c., for example: image wave 'l metres, sound wave 6.7405 metres, or image wave '7 metres, sound wave 7.28 metres. In the rst casethere is an adjustment of the local oscillator to 6.76 metres, in the second case to '7.23 metres. The correct adjustment of the local oscillator may berecognized without difficulty by the fact that with this adjustment the sound reception is at its best. In this manner there is also ensured automatically at the same time the correct adjustment of the intermediate frequency in the image receiver.

In the case of pure image receiversthere may be loosely coupled, in accordance with the invention, a circuit tuned permanently to the intermediate frequency to be adjusted and furnished with any suitable indicator (for example, luminous quartz) as desired. In this manner there is certainly also ensured the correct adjustment of the intermediate wave, but the possibility of double adjustment is not precluded.

Two forms of embodiment of the arrangement according to the invention are illustrated by way of example in the drawing, in which Fig. 1 shows an arrangement with preliminary tuning circuits, in which the three tuning condensers may preferably be adjusted (co-axially) by manual manipulation of a single knob, whilst Fig. 2 there is illustrated an arrangement without preliminary tuning, and

Fig. 3 is a partial diagram of a modication.

In the drawing l is the aerial with the wavetrap for long-wave elimination, said wave-trap comprising the condenser 2 and the resistance 3 (Fig. l) or the choke 4 (Fig. 2).

In Fig. 1, 5 and 6 are the preliminary tuning circuits connected by way of the coupling condensers I8 with the wave-trap 2, 3 for long wave elimination. The circuit 5 is tuned to the sound carrier wave, and the circuit 6 to the image carrierwave. The local oscillator 'l common to the image receiver and to the sound receiver is shown vas inductively coupled to the two circuits 5, 6; this oscillator includes a tuning condenser. The oscillations produced by the oscillator "i, together with the image wave received, are transmitted to therectifying and mixing device 8, while the sound wave received, together with the oscillations from the oscillator 1, is transmitted to the rectifying and mixing `device I2. There is thus the device 8, and the intermediate sound frequency in the device I2. The devices 8, I2 may be vacuum tubes of the type customary in the art. The intermediate frequency image wave passes from the device 8 (constituting a first rectifier) to the image intermediate frequency amplifier 9 and then to the second rectifier Ill, shown as a screen-grid audion. From this second rectifier the image-contents frequency passes to the amplifier II and then to the image receiver proper 2Q, which may be a Braun tube. At I6 and Il I have shown ohmic and inductive resistances respectively associated with the connections from the image intermediate frequency amplifier 9 to the image-contents frequency amplifier II. In the connection from the image intermediate frequency amplifier 9 to the second rectifier IEB is located a condenser 26, and a `grid leak resistance 25 is associated with said connection. These elements have battery and ground connections of a well-known type, as indicated. The intermediate frequency sound wave passes from the rectifying and mixing device I2 (constituting a first rectifier) through the circuit I5, which is tuned permanently to the intermediate sound frequency, to the sound intermediate frequency rectier I3 (constituting a second rectifier). The circuit I5 has a battery and ground connection of well-known type, as indicated. From the second rectifier I3 the sound frequency delivered by such rectifier passes to the lowfrequency sound amplifier I4 and then to the loudspeaker ZI. The preliminary tuning circuits 5, 6 include adjustable (variable) condensers as indicated, and Fig. 1 shows a single knob K for simultaneously operating said two tuning condensers of the circuits 5, 6 as well as the tuning condenser of the oscillator 'I.

In the construction illustrated by Fig. 2, the local oscillator i is connected capacitatively with the image receiver and with the sound receiver, and the preliminary tuning circuits 5, 6 of Fig. l are dispensed with. In other respects, the arrangement is substantially the same as in Fig. 1. Through the conductor 22 and the condenser I8 therein, the sound wave mixture composed of the wave received through the antenna and the local oscillations supplied by the oscillator 1, passes to the rectifying and mixing device I2 (first rectifier) and then to the circuit I5, permanently tuned to the intermediate sound frequency, to the sound intermediate frequency rectifier I3 (second rectifier), the low-frequency sound amplifier I4 and the loudspeaker 2 I, in the same manner as described in connection with Fig. 1. The image intermediate frequency amplifier 9 is connected directly with the anode circuit of the oscillator li, and the other elements of the image receiver are substantially the same as in Fig. 1, so that they need not be described again in detail. A suitable resistance with ground connection is indicated at 24. In the construction illustrated by Fig. 2, only the condenser designated at 2l is variable and used for tuning, and K designates the knob for adjusting said condenser.

The construction illustrated by the partial diagram Fig. 3 is exactly the same as Fig. 2 with respect to the elements I, 2, 4, 1, 9, I0, II, I3, I6, I5, IIS, I'i, I9, 20, 2I, 24, 25, 26,21, K and also to that condenser I8 which has a conductive connection to the choke 4; a majority of said elements have therefore been omitted from Fig. 3. In the latter, not only the image receiver produced the intermediate image frequency in circuit, but the sound receiver circuit as well is connected directly with the anode of the oscillator such connection of the sound receiver circuit being effected by the conductor 23 (with its condenser I8) leading from said anode to the permanently tuned circuit I5. This circuit I5 permits only the sound frequency to pass to the elements I3, I4, and 2|; on the other hand, the resistances I6 and I'I (arranged as in Fig. 2) prevent the passage of the intermediate frequency sound wave into the image-receiving elements of the apparatus. As in Fig. 2, only one variable condenser 21, with its operating knob K', is required in the construction represented in Fig. 3.

The audion condenser 26, in accordance with the invention, may be selected at approximately 5 cm., the grid leak resistance 25 at '75,000-100,000 ohms. Generally speaking the values of these parts are preferably so selected in accordance with the invention that the charging period, and possibly also the sum of charging and discharging period of the condenser 26 is smaller than a half-period of the modulation potential. The resistances I6 may conveniently be furnished with a value of BOOG-5000 ohms, the coils I1 with 75 windings, the resistance I9 with a value of 104 ohms, and the condensers I8 selected at 1 2 cm. 20 and 2l are the image receiver, preferably a Braun tube, and the loud-speaker. In the image intermediate frequency amplifier 9 there are preferably employed screen grid tubes as indicated in Fig. 2.

The method according to the invention ensures reliable adjustment of the best image intermediate frequency, and permits of extensive utilization of the frequency band available (situated, for example, between 6 and 9 metres). The method acquires particular importance in those localities in which the ranges of two shortwave transmitters overlap.

It will be understood that in my invention, I receive television picture waves of a certain image carrier frequency modulated with picture contents frequencies, under simultaneous reception of the accompanying sound waves of a different carrier frequency modulated with sound frequencies. The two carrier frequencies differ from each other to such an extent that a substantial gap will be left between the neighboring side bands of the modulated picture frequencies and the modulated sound frequencies respectively. The single oscillator frequency produced in my system for heterodyning with each of said carrier frequencies is chosen so as to lie between the two carrier frequencies, and more particularly in said gap between said neighboring side bands; I thus avoid all interference between the oscillator frequency and the sound-receiving as well as the picture-receiving parts of the apparatus or system.

I claim:

1. The method of receiving television picture waves of a certain image carrier frequency modulated with picture contents frequencies and simultaneously receiving the accompanying sound waves of a different carrier frequency modulated with sound frequencies, which consists in generating a single oscillator frequency lying between said carrier frequencies, heterodyning said oscillator frequency with each of said carrier frequencies to produce intermediate frequencies of predetermined wave lengths, such that the ratio of image intermediate frequency to sound intermediate frequency is of the order of about 1:10 when measured in meters, for the image and said and rectifying them, and reproducing pictures and sound from the respective rectified intermediate frequencies.

2. The method of receiving television picture Waves of a certain image carrier frequency modulated with picture contents frequencies and simultaneously receiving the accompanying sound waves of a different carrier frequency modulated with sound frequencies, which consists in generating a single oscillator frequency lying between said carrier frequencies, heterodyning said oscillator frequency with each of said carrier frequencies to produce intermediate frequencies of predetermined wave lengths, such that the image intermediate frequency is about 200 meters and the sound intermediate frequency about 2,000 meters, for the image and sound modulations respectively, separating said intermediate frequencies from each other and rectifying them, and reproducing pictures and sound modulations respectively, separating intermediate frequencies from each other sound from the respective rectied intermediate frequencies.

3. The method of receiving television picture waves of a certain image carrier frequency modulated with picture contents frequencies and simultaneously receiving the accompanying sound Waves of a different carrier frequency modulated with sound frequencies, which consists in generating a single oscillator frequency lying between and materially closer to one than the other of said two carrier frequencies, heterodyning said oscillator frequency with each of said carrier frequencies to produce intermediate frequencies of predetermined Wave lengths in such large ratio to each other as to preclude interference between said intermediate frequencies, for the image and sound modulations respectively, separating said intermediate frequencies from each other and rectifying them, and reproducing pictures and sound from the respective rectified intermediate frequencies.

KURT SCHLESINGER.

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