US2165794A

US2165794A - Television apparatus

Info

Publication number: US2165794A
Application number: US42908A
Authority: US
Inventors: Ralph S Holmes
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1935-09-30
Filing date: 1935-09-30
Publication date: 1939-07-11
Anticipated expiration: 1956-07-11

Description

July 11, 139, giHgLp/

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Witness R. s. HOLMES 2,1653% TELEVIS ION APPARATUS new i INVEN'I'OR EalphS. Holmes Patented July 11, 1939 TAT TELEVISION APPARATUS of Delaware Application September 30, 1935, Serial No. 42,908

8 Claims.

My invention relates to television apparatus and particularly to receiving apparatus adapted to receive pictures accompanied. by sound.

In Carlson Patent 1,975,056 there is described a system for the transmission of television pictures and a the accompanying sound signal in which the picture signal is transmitted on one carrier wave and the sound signal is transmitted on a separate carrier wave a fixed frequency away from it. In the receiver the two carrier waves are passed through a broadly tuned radio frequency circuit to a detector. The detector is coupled to a local oscillator which heterodynes the carrier waves to produce two intermediate frequency signals, the beats between the oscillator and the picture carrier wave and between the oscillator and the sound carrier wave.

The two intermediate frequency signals are amplified in two intermediate frequency amplifiers, rectified, and the rectified signals supplied to the cathode ray receiver tube and to the loud speaker.

A receiver such as that described above is entirely satisfactory, but it is inherently more costly than a receiver which reproduces the picture without the accompanying sound, on account of the additional functions it performs.

Since it is desirable to produce a television receiver of low cost it would be desirable to limit the requirements of the receiver to the production of the picture without the accompanying sound, provided the sound accompaniment can be obtained in some other suitable manner.

Assuming that the television picture and the accompanying sound are transmitted on separate carriers, as described in the Carlson patent, a straight picture receiver could be built at low cost, and the sound could be picked up on a standard broadcast receiver by using a suitable converter to change the transmitted sound carrier to a broadcast frequency, where it could be amplified and reproduced in the normal manner by the broadcast receiver. The disadvantage of such a system is that there are two tuning controls to be adjusted when tuning in a station, the regular picture receiver control and the tuning of the converter or of the broadcast receiver for sound. A further disadvantage is that there is no reference for tuning the picture receiver. The picture receiver has a wide frequency band, and unless there is some reference to tune by, other than the appearance of the picture itself, it is very difilcult, if not impossible, to properly tune the receiver.

It is, accordingly, an object of my invention to provide a method of and means for operating a regular broadcast receiver in conjunction with a television receiver designed to receive picture signals only without encountering the abovementioned disadvantages.

It is a further object of my invention to provide means whereby a single antenna connected to the television receiver may be employed for I either the reception of picture signals or for the reception of sound programs in the broadcast band by a broadcast receiver.

It is still a further object of my invention to provide an improved means for operating a television receiver and a broadcast receiver in conjunction with a minimum of switching.

In one of the preferred embodiments of my invention the television receiver unit is designed to operate in conjunction with a multi-band broadcast receiver having what is commonly referred to as the C band. The C band includes the 25 meter band, the 49 meter band, and several others. The television receiver is so designed that the sound intermediate frequency falls within the C band, say at 9 megacycles. This intermediate frequency signal is fed to the broadcast receiver which is switched to the C band and tuned to 9 megacycles, Thus the tuning of the broadcast receiver is fixed and the desired television stations are tuned in by operating the single tuning knob on the television receiver.

Preferably a circuit and switching arrangement is employed which causes the television receiver short wave antenna to function as a broadcast antenna for the broadcast receiver when the television receiver power switch is turned to the off position.

Other objects, features and advantages of my invention will appear from the following description taken in connection with the accompanying drawings in which,

Figure 1 is a schematic diagram of one embodiment of my invention;

Fig. 2 is a circuit diagram of an embodiment of my invention; and

Figs. 3 and 4 are circuit diagrams of other embodiments of my invention.

Referring to Fig. 1, at i there is indicated a television receiver having input terminals 2 and 3 connected through a. transmission line 5 to a suitable short wave antenna l such as an antennaof the dipole type. The end of a cathode ray tube upon which the picture appears is indicated at 6. The receiver is provided with an on-01f switch 1 (Fig. 3) which preferably may be operated by the same knob 3 that controls the brightness of the picture, or some other characteristic thereof, such as detail.

In a preferred embodiment of the invention, which will be described later, the same knob 8 which operates the on-off or power switch also operates an antenna switch 9 (Fig. 3) for the purpose of making the antenna 4 function as a short wave antenna when the power switch is on and as along wave antenna when the power switch is off. The tuning knob of the television receiver is indicated at H.

The television receiver I is provided with an output terminal I2 for conveying the sound signals accompanying the picture signals to a broadcast receiver of conventional design indicated at I3. One input terminal I4 (the ground post) of the broadcast receiver I3 is connected to ground while the other input terminal l6 (the antenna post) may be connected through a switch arm II either to a long wave or broadcast receiving antenna I8 or to a contact point I9 which is connected to the sound output terminal I2 of the television receiver I.

The broadcast receiver I3 is provided with the usual loud speaker 2|, power switch 22, Wave band switch 23 and tuning dial 24.

The circut diagram for the apparatus shown in Fig. l is shown in Fig. 2. Referring to this figure, the television receiver comprises a tunable selecting circuit 23 which is tuned broadly enough to pass both the sound carrier and the picture carrier radiated from a transmitting station. The selecting circuit 25 consists of two coupled tuned circuits 21 and 28 each of which may be shunted by a resistor for the purpose of broadening the tuning. A suitable short wave antenna, indicated by a conventional symbol at 29, is coupled to the input side of the selecting circuit 26.

The output side of the selecting circuit 26 is connected to the input terminals of a first detector 3|, this detector being coupled to a tunable oscillator 32 for the purpose of heterodyning the incoming carrier waves to intermediate frequency signals. The selecting circuit 26 and the oscillator 32 may be tuned simultaneously by the single tuning knob II in accordance with usual practice.

The intermediate frequency picture signal is transferred from the output circuit of the first detector 3| through a secondary winding 34 of a broadly tuned intermediate frequency transformer to an intermediate frequency amplifier'36, and through another broadly tuned intermediate frequency transformer 31 to such other intermediate frequency amplifiers as are necessary. After suitable amplification, the intermediate frequency picture signal is detected in a second detector to obtain the picture signal which is then amplified and supplied to the cathode ray tube 6.

The intermediate frequency sound signal which appears in the output circuit of the first detector 3| is transferred to a comparatively sharply tuned secondary winding 38, which is loosely coupled to the detector output circuit, and fed to the sound output terminal I2. The conventional broadcast receiver I3 may then be connected either to the long wave length antenna for receiving ordinary sound broadcast programs or to the output terminal I2 for receiving the sound accompanying the picture, as previously explained.

It will be understood that when receiving television programs the tuning of the broadcast receiver is fixed and that all tuning is done by means of the single tuning knob I I on the television receiver. In operating the picture receiver unit I and the broadcast receiver I3 in conjunction, the switch ll is moved to the position indicated in Figs. 1 and 2 and the band switch 23 is turned to the desired band such as the C band. The broadcast receiver I3 is then tuned to a predetermined position which may be marked on the tuning dial 24 by the letter T as indicated in Fig. l'to tune the broadcast receiver to the intermediate frequency sound signal.

It will be apparent that it is desirable to eliminate the long wave antenna I8 and connect the broadcast receiver I3 permanently to the television receiver I whereby operation of one switch is eliminated. This may be accomplished by means of a circuit such as shown in Fig. 3 in which parts similar to those in Figs. 1 and 2 are indicated by the same reference numerals. Re-

' ferring to Fig. 3 the television input terminals 2 and 3 are connected to a suitable short wave antenna such as an antenna of the dipole type or an antenna of the Zeppelin or voltage fed type. The input terminals 2 and 3 are connected to an input coil 39 which is coupled to a tunable selecting circuit 4| comprising two coupled resonant circuits. As previously described, the selecting circuit is tuned broadly enough to permit both the sound carrier and the picture carrier to pass thereunder to a first detector.

The tunable oscillator 32 heterodynes the incoming signals to intermediate frequency signals. The intermediate frequency picture signal is taken from the output circuit of the first detector 3i by means of a tuned circuit 42. The signal is then suitably amplified in'intermediate frequency amplifiers, detected, and again amplified and supplied to the cathode ray tube 6.

The intermediate frequency sound signal is taken from the output circuit of the first detector 3! by means of a coil 33 which is coupled thereto and which has one end connected to the midpoint of the input coil 39 through a conductor 44. The other end of the coil 13 is connected to the sound output terminal i 2 of the television receiver.

The antenna post I6 of. a multi-band broadcast receiver 13 such as previously described is connected through a shielded conductor 36 to the sound output terminal i2 of the television receiver. The ground post I4 of the broadcast receiver is connected to ground in the usual manner.

The antenna switch 9 is provided which when closed, or in the on position, connects the midpoint of the input coil 39 to ground.

Filament current and a suitable direct current voltage are supplied to the television receiver from any suitable power supply such as a 110 volt line. This line is shown connected through the power switch "I to the primary winding of a transformer 41. A low voltage secondary winding 48 is. connected to the heater filaments of the various vacuum tubes which filaments may be connected in parallel as shown in the drawings. A high voltage secondary winding 49 is connected to a suitable rectifier and filter unit indicated at for supplying the necessary direct current potentials.

As described in connection with Fig. 1, the antenna switch 9 preferably is interlocked or connected to the power switch I whereby the two switches. are operated simultaneously by the actuation of a single knob such as the knob 8 shown in Fig. 1. r

From the foregoing description, it will be seen that when the power switch is tuned on, the midpoint of the input' coil 39 is connected to ground whereby the dipole antenna 4 (Fig. 1) or other short wave antenna connected to the input terminals 2 and 3 will function in the usual manner as a short wave antenna to supply the high frequency sound and picture carrier to the selecting circuit 4|. In this case, the intermediate frequency sound signal will be transferred from the detector output circuit to the coupling coil 43 and through the shielded conductor 46 to the input terminals of the broadcast receiver l3. Therefore, the picture signal will be received by the television receiver unit i and the accompanying sound will be received by the broadcast receiver 13.

When the power switch of the television receiver is turned off, the midpoint of the input coil 39 will no longer be grounded and the short Wave antenna d and the transmission line 5 (Fig. 1) connecting it to the input terminals 2 and 3 will function as a long wave antenna. Therefore, sound signals within the broadcast range will be supplied through the conductor 44, the coupling coil 43 and the shielded conductor dB to the antenna terminal iii of the broadcast receiver. It will be apparent that by utilizing this circuit and switching arrangement I not only avoid the necessity of employing two separate antennas but I also simplify the operation of the television and broadcast receiver units.

Referring to Fig. 4, there is shown an embodiment of my invention in which the intermediate frequency sound signal is transmitted over a transmission line 52 to the sound unit. Like parts in Figs. 3 and 4 are indicated by the same reference numerals. It the sound unit indicated at 53 is a broadcast receiver, as in the previously described receiving systems, the switch 9 is employed for grounding the midpoint of the input coil 39 during the reception of television signals. When the switch is in this position, as shown in the drawings, the intermediate frequency sound signal is transferred from the output circuit of the detector 3! to the coil 43 and is transmitted over the two

transmission line conductors

54 and 56 to the sound unit 53. When the switch 9 is open, the short wave antenna and its transmission line function as a long wave antenna, as previously described, and the comparatively low frequency sound modulated carrier waves pass through the inductance coil 43, over the conductor 54 to the sound unit 53 and back through the other conductor 56 to ground at a point in the television receiver.

It has been found that under certain circumstances it is desirable to employ a transmission line inside a television receiver cabinet itself. It has been the usual practice to mount the picture signal apparatus and the sound signal apparatus on a common chassis. Greater flexibility in receiver design is possible if the sound unit and the picture unit are built on separate chassis. By employing this design, sound units capable of reproducing sound with either moderate or high fidelity may be combined with picture receiver units which likewise may be capable of reproducing pictures with either moderate or high fidelity.

It is possible to employ two separate reproducing units in a single receiver cabinet, as described above, by employing a transmission line for transferring the intermediate frequency sound signal from the first detector to the sound unit.

When this receiver design is employed, the switch 9 is replaced by a permanent connection and the sound unit 53 consists of a plurality of intermediate frequency amplifiers, a second detector and an audio frequency amplifier.

While it is preferred to employ a short wave antenna connected through a transmission line to an input coil grounded at its midpoint, fairly good picture signal reception may be obtained by connecting an antenna to only one end of the input coil. In that case, one half of the input coil is not used.

From the foregoing description it will be apparent that various other modifications may be made in my invention without departing from the spirit and scope thereof and I desire, therefore, that only such limitations shall be imposed there on as are necessitated by the prior art and are set forth in the appended claims.

I claim as my invention:

1. In combination, a television receiver and a broadcast sound receiver, a short wave antenna, a transmission line connecting said antenna to said television receiver, and switching and circuit means for selectively utilizing said antenna as a short wave antenna for said television receiver or said antenna and said transmission line in combination as a long wave antennna for said broadcast receiver.

2. In combination, a television receiver and a broadcast sound receiver, an input coil in said television receiver, a short wave antenna, a transmission line connecting said antenna to said input coil, a connection between said input coil and said broadcast receiver, and means including a switch for grounding the midpoint of said input coil for selectively utilzing said antenna as a short wave antenna for said television receiver or said antenna and said transmission line in combination as a long wave antenna for said broadcast receiver.

3. The invention according to claim 2 characterized in that said television receiver includes a power switch and means for so connecting said power switch to said first switch that said midpoint is grounded in response to said power switch being turned on and disconnected from ground in response to said power switch being turned ofi.

4. In combination, a television receiver comprising an input coil at least one end of which is to be connected to an antenna and a point on which is to be connected to ground, means for converting incoming picture and sound carrier waves to intermediate frequency picture and sound signals, means comprising a selecting circuit for transferring said incoming carrier Waves from said input coil to said converting means when said point is grounded, a broadcast sound receiver, means including an inductance coil for coupling the output circuit of said converting means to said broadcast receiver whereby said intermediate frequency sound signal is transferred thereto when said point is grounded, said coupling means including a connection from one end of said inductance coil to an input terminal of said broadcast receiver, a connection from said point to the other end of said inductance coil, and an antenna switch for connecting said point to ground when desired.

5. In combination, a television receiver comprising an input coil having antenna terminals and a midpoint, means for converting an incoming signal to an intermediate frequency signal, means comprising a selecting circuit for transferring said incoming signals from said input coil to said converting means when said midpoint is grounded, a broadcast sound receiver, coupling means for coupling the output circuit of said converting means to said broadcast receiver whereby an intermediate frequency is transferred thereto when said midpoint is grounded, a connection from said midpoint to said coupling means whereby signals are transferred directly from said coupling coil to said broadcast receiver when said midpoint is not grounded, and an antenna switch for selectively connecting or disconnecting said midpoint to or from ground.

6. The invention according to claim 5 characterized in that the television receiver is provided with a power switch for energizing it, and further characterized in that said antenna switch and said power switch are so connected that when said power switch is 7 closed said midpoint is grounded and when said power switch is open said midpoint is not grounded.

7. The invention according to claim 5 characterized in that said coupling means comprises an inductance coil having one end connected to said midpoint and the other end connected to an input terminal of the broadcast receiver.

8. In a radio receiver for receiving signals from a short wave energy collector through a transmission line, a broadly tuned frequency convertor portion, a relatively sharply tunable beat-frequency amplifier portion, and switching and circuit means for effecting a connection from said energy collector to either portion, said means including a coupling winding adapted to be conn'ected at each end through said transmission line to said energy collector, a coupling circuit connected to the midpoint of said winding and to said beat-frequency amplier portion, said switching means including contacts for grounding said midpoint of the coupling winding when receiving short wave signals.

RALPH S. HOLMES.