Abstract: In a method for calibrating or aligning a multistage selective amplifier including an oscillator circuit and at least one tuning circuit, the tuning voltages respectively necessary for aligning the respective tuning circuits to the required receiving frequency are calculated directly from a mathematical relationship between the respective tuning voltage and the oscillator voltage. In order to achieve this, a characteristic multiplicative coefficient and a characteristic additive factor for each tuning circuit are stored in a memory upon manufacturing or switching on the device. In order to select a desired receiving frequency, the respective stored values as well as an oscillator voltage are provided to an amplification circuit, which correspondingly amplifies the oscillator voltage by the multiplicative coefficient and the additive factor and then provides the resulting output value as a tuning voltage to the respective tuning circuit.

Abstract: The invention concerns an I.F. filter arrangement in a receiver for receiving FM signals. An I.F. filter arrangement is to be provided which no longer contains the disadvantageous effects of a control loop from which a control value is extracted from the MPX signal to be used for tracking the I.F. filter. The solution according to the invention is an I.F. filter arrangement having a filter device which comprises a defined, in particular, a fixed adjusted bandpass region and at least two outputs having center frequencies staggered with respect to one another or I.F. frequencies staggered with respect to one another at the same center frequency. The signals from the outputs are fed to a weighting device which is regulated by a control value extracted from the demodulated FM signal.

Abstract: A method and circuit for suppressing periodic noise interference in a broadcast signal received by a receiver, in which, during reception of the broadcast signal a dip occurs in the amplitude of the received broadcast signal each time noise interference is present, each dip having a slope, by the steps of: determining the values of the amplitude of the received signal; setting a basic received signal threshold value which is less than the value of the received signal at a time when no noise interference is present; during each occurrence of noise interference, increasing the threshold value by an amount proportional to the slope of the corresponding dip in the amplitude of the received signal; and acting on the received signal to suppress noise interference during a time when the amplitude of the received signal is below the increased threshold value produced by the increasing step.

Abstract: For suppressing interference signals in a multiplex signal an RC member which is preceded by a voltage divider is used. The voltage divider consists of a resistor and two diodes which are connected in parallel and in opposite directions and which perform a limitation with respect to a reference signal taken from the output of a fedback differential amplifier. The output signal of the RC member is applied to the non-inverting input of the differential amplifier. The limitation is carried out with respect to a reference signal corresponding to the signal smoothed by the RC member.

Abstract: The tuning system for a high frequency receiver, particularly an AM receiver for vehicles, comprises a tunable input resonance circuit having a variable inductance formed by the signal winding of a controllable inductor. The control winding of the inductor is supplied with a control current. The control winding is simultaneously used as the frequency determinative element of an auxiliary oscillator. A frequency control loop is used to adjust the oscillating frequency of the auxiliary oscillator by adjustment of the control current. The tuning system allows a selective coupling between the tuned antenna input circuit and the rf front end of the receiver.