DE1014587B - Switchable multipurpose oscillator in combined radio and television sets - Google Patents

Description

GERMAN

It is desirable for economic reasons in a combined radio and television receiver largely for VHF radio reception that uses frequency-modulated vibrations Use parts of the television. It is known to be useful in devices with a differential carrier tone to apply the principle of double superposition: the VHF signal passes through the High-frequency part (with the first mixer) and the picture IF part and is made by a second mixer converted to the differential carrier frequency, which is then fed to the audio part of the television receiver.

It is also known that as an oscillator tube for the second mixer with the help of a switch a tube in the image part of the device is used. But it is always very undesirable to use high frequency To switch potentials, since the switch is often not spatially in the immediate vicinity the tube or the circle can be attached.

In the circuit according to the invention, a direct changeover switch is not necessary, since the operation of the the tube belonging to the picture part was chosen so that by switching a DC voltage the Tube is converted into a mixer oscillator. This was achieved by the fact that the Tube for television reception in a known manner as a commuter to generate a sawtooth voltage is working. The pendulum frequency must be the one desired to deflect the electron beam The picture tube corresponds to the required tilting frequency. The oscillation frequency of the oscillating circuit is allowed in this Function in itself can be arbitrary. The same resonant circuit is now used in the circuit according to the invention unchanged also as a frequency-determining element for the mixer oscillator in VHF radio reception is used, and the pendulum process is suppressed in the "radio" position, so that the oscillator oscillates freely and takes over the function of the second mixer oscillator for VHF broadcasting can. The frequency of the resonant circuit must now correspond to the required oscillator frequency.

The circuit according to the invention is explained in more detail with reference to the drawing:

In the "television" position, the voltage + A is switched on, so that the diode 1 is flowed through by the current and thus performs the task of a low-ohmic resistor. The capacitor 2 is thus practically grounded. The oscillator 3 will oscillate with its oscillator circuit 4. On the convertible multi-purpose oscillator
in combined radio television sets

Applicant:

Körting Radio Werke GmbH,
Grassau (Chiemgau)

Günther Gassmann, Staudach (Obb.),
has been named as the inventor

capacitor 2 is the sawtooth voltage, which is fed via the output 5 of the corresponding deflection output stage will. The voltage + A is the supply voltage for the tubes, which are used for FM radio reception are superfluous. In the »radio« position it is switched off. At the same time this is the current interrupted by the diode 1, so that the diode resistance rises far and the pendulum oscillation stops and the oscillator swings freely. Part of the oscillator voltage can now be used via the capacitors 2 and 6 reach output 7 and are thus fed to the picture IF channel for the purpose of mixing.

Claims (1)

PATENT CLAIM: Switchable general-purpose oscillator in combined radio and television sets, either works as a normal oscillator for radio reception and converts the intermediate frequency serves or works as a pendulum level when receiving television and directly or indirectly for generation a deflection voltage or a deflection current of the picture tube is used, characterized in that the same resonant circuit that determines the frequency in the first operating mode for the oscillator The second operating mode is used unchanged as a pendulum circle. Considered publications:
German Patent Nos. 548 384, 657 457;
Austrian Patent No. 177 816;
"Television and sound film", March 1940, p. 10. 1 sheet of drawings