US2173496A - Television transmitter - Google Patents

Television transmitter Download PDF

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Publication number
US2173496A
US2173496A US70424A US7042436A US2173496A US 2173496 A US2173496 A US 2173496A US 70424 A US70424 A US 70424A US 7042436 A US7042436 A US 7042436A US 2173496 A US2173496 A US 2173496A
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US
United States
Prior art keywords
image
grid
modulator
modulator system
carrier
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US70424A
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English (en)
Inventor
Schlesinger Kurt
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Loewe Opta GmbH
Original Assignee
Loewe Opta GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Loewe Opta GmbH filed Critical Loewe Opta GmbH
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Publication of US2173496A publication Critical patent/US2173496A/en
Anticipated expiration legal-status Critical
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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/04—Synchronising
    • H04N5/06—Generation of synchronising signals
    • H04N5/067—Arrangements or circuits at the transmitter end
    • H04N5/0675—Arrangements or circuits at the transmitter end for mixing the synchronising signals with the picture signal or mutually
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C1/00—Amplitude modulation
    • H03C1/16—Amplitude modulation by means of discharge device having at least three electrodes
    • H03C1/18—Amplitude modulation by means of discharge device having at least three electrodes carrier applied to control grid
    • H03C1/24—Amplitude modulation by means of discharge device having at least three electrodes carrier applied to control grid modulating signal applied to different grid
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/38—Transmitter circuitry for the transmission of television signals according to analogue transmission standards
    • H04N5/40—Modulation circuits

Definitions

  • the modulation of the radio-frequent carrier wave is performed at one single terminal of the modulating device, for example at the control grid of 80 the modulating tube, it is necessary to mix the potentials of the image contents and the synchronisation impulses before entry into the modulator.
  • careful consideration must '86 be paid to the law relating to difference in amplitude. It has been found in practice that in the case of a "single-channel modulation of this kind interferences frequently occur in the synchronisation. Even if the amplitude diagram of 40 the heterodyned image and synchronisation oscillations' reveals the correct relative difference in amplitude, that is to say.
  • the medium absolute potential of the diagram fluctuates for any reason in relation to earth. It may, therefore, very easily occur that either the peaks of the synchronisation impulses no longer reach the potential value which is required for the complete range of the aerial current, or it may also occur that the medium potentials sink to such extent that also the strongest image signals are able to suppress the aerial current, whereby in the first case there occurs consists of impulses which are disa breakdown in the synchronisation and in the second case a faulty synchronisation by reason of the contents of the image.
  • This device termed level-maintaining means, natural-' 15 ly also possesses a certain inertia, as the same upon its function requires to charge condensers, and it is, therefore, diflicult to avoid that an occasional potential peak of the image amplifier exceeds the maximum permissible value and passes into the synchronisation range. In this manner also there is caused: an error in synchronisation even when due care is taken to maintain the absolute values of the impulse peaks in relation to earth.
  • the fundamental object of the present invention to simplify and to facilitate the operation of a television transmitter of this kind, which performs synchronisation by differences in amplitude.
  • the method according to the invention departs fundamentally from the single-channel method, and-makes use of transmission means having more than one modulation input.
  • Fig. 5 is a diagrammatic ciple arrangement according to the present invention.
  • the transmitter accordingly possesses two modulators,. which in accordance with the invention are connected in series.
  • Fig. 1 discloses s5 showing of the min- 50 exactly the properties of these modulators.
  • the first channel is the image potential channel.
  • the same comprises the output line of the image-current amplifier l, which is employed, for examplenot essentially-for scanning the film 2 by means of the photo-cell 3.
  • Its output line 4 enters a level-maintaining means 5. This has the property of ensuring that the maximum peak values in a certain direction of sign, for example the most negative peaks corresponding with bis-ck" in the image, are unable to drop below a certain absolute value in relation to earth.
  • This value which is represented in broken lines by a battery 6, amounts for example to -5 volts, assuming the radio transmitter is fully controlled down to zero with approximately -l volts.
  • the level-maintaining means may ensure that on the whole negative peaks of more than 5 volts do not occur during the entire transmission. Whereas in the case of the single-channel methods it has been necessary to rely solely on the proper functioning of 5, it is accomplished according to the present invention that in the case grid bias.
  • the line 1 conducts the image potentials thus regulated to the first modulator 8 of the transmitter.
  • This is shown in its most simple form as a threepole tube 9 with grid modulation.
  • the grid is adjusted by the negative bias 6, which prevails in the case of black, to the range of the lower bend, but at no time in such negative fashion that the high-frequency anode current flowing by reason of the foreign excitation at the radio' transmitter l0 disappears entirely. It is assumed that the point of disappearance is located at 10 volt 6 is then adjusted, for example, to -5 volts, and fluctuates during the transmission, for example, between 5 and +20.
  • the shunt condenser H by-passing the tube 9, transmits oscillations of radio frequency to the anode in the same phase in which they would also reach the anode through the medium of the electronic current. If the condenser II were missing, the aerial oscillations would cease entirely at ---10 volts and still more negative biases. By reason of the shunt II a cessation at all of the aerial oscillations is rendered impossible. They are at no time able to drop below a minimum value which is adjustable by means of l l.
  • Fig. 2 there is shown anaerial current diagram which would occur in the case of a television transmission if the image channel .I and the modulator 9 were employed alone.
  • the minimum height I! ofthe aerial current amplitudes is set by adjustment of the condenser Ii. If the amplitude filter of the receiver is likewise located with its threshold of .response at l2, the image transmission can fundamentally at no time synchronize the reception.
  • a second synchronization modulator which in accordance with Fig. 1 is constituted as follows:
  • a synchronization generator which is composed, for example, of a perforated disc is and photo-amplifier ll, supplies to the edge of the image through the medium of a condenser impulses of negative sign and constant intensity.
  • the synchronization channel I! possesses earth, potential.
  • the line I excites a second modulator I8.
  • This modulator has the property of being able'to perform a complete suppression of the anode current if its control grid is sufilciently negatively biassed. This requirement is merely capable of being performed by the use of a screening grid tube II, the screening grid of which is earthed as faras possible without resistance by earthing condensers, or still better by means of a short circuit "I", which is tuned to resonance with the carrier wave.
  • the synchronization modulator It must accordingly represent a pure electronic coupling and be free from shunts pertaining to connections of any kind (in contradlstinction to the image modulator I).
  • a modulator which is excited by a foreign source and to which the radio excitation is conducted by means of a control transmitter l9, which oscillates in the known manner, for example in crystal-controlled fashion, with constant amplitude and frequency.
  • Fig. 2 there is indicated at 20 a synchronization signal which performs complete suppression of the aerial current because at this point the image modulator 9 has been deprived of the highfrequency excitation by the synchronization modulator.
  • Fig. 1 there have been shown for the purpose of better comprehension two separate modulating valves. It is possible, however, to utilize the idea according to the invention in more simple form, making use of merely one single penwde. An embodiment of this kind, which has been found to be very good in practice, is illustrated in Figs. 3 and 4.
  • the modulating stage of the transmitter possesses two control electrodes, which are independent of each other but are situated in the common path of discharge, and one each of which is modulated with the image current and with the synchronization current respectively.
  • the modulating tube is of such kind that upon blocking the synchronization electrode it is impossible to pass electronic current through the tube even if the image-way should be open. An operation of this kind is readily obtained for monic of the example withinterengaging cylindrical control grids, such as usual in the case of hexodes.
  • Fig. 3 there is applied to the first grid.2
  • the screening grid 23 is completely earthed dynamically as far as is technically possible, preferably by means of a series resonance cirthat between the control grid 2
  • the image modulation is conducted to the reflector grid 24.
  • This grid is closed oil for high frequency in highly'ohmic fashion by means of a choke 25, and is accordingly able to perform the oscillations of the high frequency.
  • the grid 24 may be more or less short-circuited for high frequency, and by means of a very small neutrode 21, which certainly is frequently rendered unnecessary by reason of the inner capacity between reflector grid and anode, a coupling of both electrodes may be adjusted.
  • the anode circuit is tuned to a hargrid circuit 2
  • connection system So long as the control. grid 2
  • Fig. 4 shows a particular form of embodiment of the idea according to the invention having the special feature that the high-frequency carrier wave is conducted to the modulating tube at a third, separate electrode '(control circuit), and that the anode circuit of the modulating tube is tuned to a higher harmonic of this control frequency.
  • I is the multi-grid modulating tube according to the invention.
  • the control frequency is applied to the innermost grid 2 of the same. This, for example, is one-half. of the operating frequency to be radiated by the aerial. It is supplied through. the medium of a coupling '3 by a preferably quartz-controlledcontrol transmitter l. This transmitter accordingly operates on the l-metre wave if the transmission is to be radiated on a7-metre wave.
  • a bias 5 the control grid 2 is blocked in such fashion that merely the most extreme positive peak values of the control frequency 4 are able to produce an electronic current in I.
  • the next grid 6 For the modulation with image currents there is employed for example the next grid 6.
  • the synchronisation modulation takes place in accordance. with the invention at a special control grid I5.
  • the intercepting grid of The synchronisation modulation consists of short and long impulses
  • the impulse signals are of such intensity .that the anode current is completely suppressed by the same or withheld by the intercepting grid l5 respectively. In this way it is accomplished, dependent on the particular potential condition of the screeninggrid circuit, that the aerial current essentially disappears in each case upon the transmission of the synchronisation signals.
  • the 14-metre oscillation excited by the-control circuit 2/3, after traversing the two separate modulating grids of the pentode The same meets here with an operating circuit l8, l9, which in accordance with the invention is tuned to a higher harmonic 4, for example a 7-metre circuit, and from this point, after a power amplifier 20 has been employed, may be conducted to an aerial 2
  • modulating circuits 6 and I5 require to be blocked against thecontrol frequency. s takes place by means of small condensers 22, 23 of approximately 50 to 100 cm. and shortwave chocks 24, 25, which prevent the ultra-high frequency from penetrating into the modulating circuits 9 or I6.
  • FIG. 5 In Fig. 5 the idea accordin to the invention is illustrated once more in pur y diagrammatical form, and it is obvious that this idea may be performed by means of a large number of equivalent connection systems.
  • a modulator Ms is a pure 1 electronic coupling; the high-frequencyv excitation is shown as electromotive force I! and passes its current through the synchronisation modulator Ms and the image modulator Ms. Whilst the modulator Ms may be made completely nonconductive by the synchronisation generator ii,
  • the image modulator Me is maintained permanently in a weakly conductive condition by the small shunt condenser i I. Even if the image current amplifier I makes it itself non-conducgo tive an exciter current from the E. M. F. I! is still able to reach the aerial transformer 28 so long as Ms performs conduction.
  • the essential matter viz., the series connection of a fully controllable and a bridged modulator and their connection with two channels, image current and synchronisation current, is shown in its most general form.
  • a television circuit system for modulating a carrier wave with image-contents signals and synchronizing impulses comprising a first and a second modulator system, a carrier frequency generator, a synchronizing impulse frequency generating circuit connected to said first modulator system, an image-contents signal frequency generating circuit connected to said second modulator system, an output circuit connected to an aerial circuit said synchronizing impulse fredl quency generating circuit being adapted to reducing to zero said carrier, the first modulator system being so connected with respect to said second modulator system that the carrier current flowing through said second modulator system is 0 dependent on the operation of said first modulator system, the use of special means within said second modulator system for preventing said image-contents signal frequency generating circuit from reducing to zero said carrier said special means comprising an impedance arranged between said image-contents signal'clrcuit and said output circuit.
  • a television circuit system for modulating a carrier wave with image-contents signals and synchronizing impulses comprising a first and a second modulator system, a carrier frequency generator, a synchronizing impulse frequency generating circuit connected to said first modulator system, an image-contents signal frequency generating circuit connected to said second modulator system, an output circuit connected to an aerial circuit said synchronizing impulse frequency generating circuit being adapted to reducing to zero said carrier, the first modulator system being so connected with respect to said second modulator system that the carrier current flowing through said second modulator system is dependent on the operation of said first modulator system,
  • first modulator system including a screening grid valve.
  • control grid of which is connected to said synchronizing impulse frequency generating g circuit and said carrier frequency generator
  • said second modulator system including a modulator valve having at least cathode, control grid and anode, the control grid of which is connected to said image-contents frequency generator circuit 10 of said screening grid valve said special means comprising an impedance arranged between said image-contents signal circuit and said output circui 3.
  • a television circuit system for modulat- 1 ing a carrier wave with image-contents signals and synchronizing impulses comprising a first and a second modulator system, a carrier frequency generator, a synchronizing impulse frequency generating circuit connected to said first modua lator system, an image contents signal frequency generating circuit connected to said second modulator system, an output circuit connected to an aerial circuit said synchronizing impulse frequency generating circuit being adapted to re- 55 ducing to zero said carrier, the first' modulator system being so connected with respect to said second modulator system that the carrier current flowing through said second modulator system is dependent on the operation of said first modugo lator system the use of'special means within said second modulator system for preventing said image-contents signal frequency generating circuit from reducing to zero said carrier, said first modulator system including a screening grid 3 valve, the control grid of which is connected to said synchronizing impulse frequency generating circuit and said carrier'frequency generator, the screening-grid being short-circuited by means of a resonance circuit tuned to said carrier,
  • a television circuit system for modulating a carrier wave with image-contents signals and 5 synchronizing impulses comprising a first and a second modulator system, a carrier frequency generator, a synchronizing impulse frequency generating circuit connected to said first modulator system, an image-contents signal frequency 5 generating circuit connected to said second modulator system, said synchronizing impulse frequency generating circuit being 'adapted to reducing to zero said carrier, the first modulator system being so connected with respect to said second modulator system that the carrier current flowing through said second modulator system is dependent on the operation of said first modulator system, the use of special means within said second modulator system'for preventing said image-contents signalfrequency generating circuit from reducing to zero said carrier, said first modulator system including ascreening grid valve, the control grid of which is connected to said synchronizing impulse frequency generating circuit and said carrier frequency generator, said second modulator system including a modulator valve having at least cathode, control grid and anode, the control grid of which is connected to said image contents frequency generator circuit second modulator
  • a television circuit system for modulating a carrier wave with image-contents signals and synchronizing impulses comprising a first and a second modulator system, a carrier frequency generator, a synchronizing impulse frequency generating circuit connected to said first modulator system, an image-contents signal frequency generating circuit connected to said second modulator system, said synchronizing impulse frequency generating circuit being adapted to reducing to zero said carrier, the first modulator system being so connected with respect to said second modulator system that the carrier current flowing through said second modulator system is dependent on the operation of said first modulator system, the use of special means within said second modulator system for preventing said imagecontents signal frequency generating circuit from reducing to zero said carrier, said first and second modulator system being combined within a -electrode valve having cathode, anode] and three grids, the first grid numbered from the cathodebeing connected to said synchronizingimpulse frequency generating circuit and said carrier frequency generator, the second grid being the screening grid and connected to ground via a resonance circuit tuned to said carrier
  • a television circuit system for modulating a carrier wave with image-contents signals and synchronizing impulses comprising a first and a second modulator system, a carrier frequency generator, a synchronizing impulse frequency bined within a 5-electrode valve generating circuit connected to said first modulator system, an image-contents signal frequency generating circuit connected to said second modulator system, said synchronizing impulse frequency generating circuit being adapted to reducing to zero said carrier, the first modulator system being so connected with respect to said second modulator system that the carrier current flowing through said second modulator.
  • the use of special means within said second modulator system for preventing said image-contents signal frequency generating circuit from reducing to zero said carrier said first and second vmodulator system being combined within a 5-electrode valve having cathode, anode and three grids, the first grid numbered from the cathode being connected to said synchronizing impulse frequency generating circuit and said carrier frequency generator, the second grid being the screening grid and connected to ground via a resonance circuit tuned to said carried, the third grid being connected to said image-contents frequency generating circuit, and via a variable condenser to ground, said special means consisting of a variable condenser connected between said third grid and said anode.
  • a television circuit system for modulating a carrier wave with image-contents signals and synchronizing impulses comprising a first and a a carrier frequency second modulator system, generator, a synchronizing impulse frequency generating circuit connected to said first modulator system, an image-contents signal frequency generating circuit connected to saidsccond modulator system, said synchronizing impulse frequency generating circuit being adapted to reducing to zero said carrier, the first modulator system being so connected with respect to said second modulator system that the carrier current flowing through said second modulator system is dependent on the operation of saidfirst modulator system, the use of special means within said second modulator system for preventing said image-contents signal frequency generating circuit from reducing to zero said carrier, said first and second modulator system being comhaving cathode, anode and three grids, the first grid numbered from the cathode being connected to said synchronizing impulse frequency generating circuit and said carrier frequency generator, the second grid being the screening grid and connected to ground via a resonance circuit tuned to saidgenerator, a synchron
  • said-first and second modu-.- lator system being combined within a 5-electrode valve having cathode, anode and three grids, the first grid numbered from the cathode being connected to said carrier frequency generator, the second grid being connected to 'said image-contents irequenoy generating circuit via a peak potential levelling arrangement. the third grid being connected to said synchronizing impulse generating circuit.
  • a television circuit system for modulating a carrier wave with image-contents signals and synchronizing impulses comprising a first and a second modulator system, a carrier frequency generator, 9. synchronizing impulse frequency generating circuit connected to said first modulator system, an image-contents signals frequency generating circuit connected to said second modulator system, said synchronizing impulse irequency generating circuit being adapted to rcducing to zero said carrier, the first modulator system being so'connected with respect to said second modulator system that the carrier current flowing through said second modulator system is dependent on the operation of said first modulator system, said first and second modulator system being combined withina li-electrode valve having cathode, anode and three grids, the first grid numbered irom the cathode being connected to said carrier frequency generator, the second grid being connected to said image-contents frequency generating circuit via a peak potential levelling arrangement, the third grid being connected to said synchronizing impulse generating circuit, the anode being connected to an output circuit tuned to the double frequency value of

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Television Systems (AREA)
  • Synchronizing For Television (AREA)
  • Transmitters (AREA)
US70424A 1935-03-28 1936-03-23 Television transmitter Expired - Lifetime US2173496A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DER92959D DE648402C (de) 1935-03-28 1935-03-28 Anordnung zur Modulation der Traegerwelle eines Fernsehsenders mit Bildinhaltsspannungen und den in Bildpausen gegebenen Synchronisierzeichen

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Publication Number Publication Date
US2173496A true US2173496A (en) 1939-09-19

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US70424A Expired - Lifetime US2173496A (en) 1935-03-28 1936-03-23 Television transmitter

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US (1) US2173496A (xx)
BE (1) BE414633A (xx)
DE (1) DE648402C (xx)
FR (1) FR804325A (xx)
GB (1) GB472900A (xx)
NL (1) NL58585C (xx)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2469606A (en) * 1945-10-25 1949-05-10 Farnsworth Res Corp Video signal level control
US2609509A (en) * 1945-06-13 1952-09-02 Bertram C Hill Electrical testing apparatus
US2879501A (en) * 1953-04-30 1959-03-24 Baran Paul Null-responsive ratio-modulation multiplex data transmission systems
US2962549A (en) * 1955-03-30 1960-11-29 Alden Products Co Method and apparatus for generating facsimile signals

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL74227C (xx) * 1948-09-11

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2609509A (en) * 1945-06-13 1952-09-02 Bertram C Hill Electrical testing apparatus
US2469606A (en) * 1945-10-25 1949-05-10 Farnsworth Res Corp Video signal level control
US2879501A (en) * 1953-04-30 1959-03-24 Baran Paul Null-responsive ratio-modulation multiplex data transmission systems
US2962549A (en) * 1955-03-30 1960-11-29 Alden Products Co Method and apparatus for generating facsimile signals

Also Published As

Publication number Publication date
GB472900A (en) 1937-09-28
NL58585C (xx)
DE648402C (de) 1937-07-30
BE414633A (xx)
FR804325A (fr) 1936-10-21

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