Abstract: A control signal generator for use with a broadcast receiver having a signal level indicator including a plurality of sequentially actuated luminous elements. The received signal strength is indicated by the number of luminous elements which are lit. The control signal generator is responsive to the signal level indicator to provide control signals for automatic frequency control circuitry and/or muting circuitry. The signal level indicator may include cicuitry for converting arbitrarily selected changes in the received signal to changes the indicator normally detects to thereby effect the sequential actuation of the luminous elements in accordance with the arbitrarily selected changes in the received signal.

Abstract: A phase-locked loop (PLL) circuit and a synthesizer tuner incorporating the PLL circuit where a second DC control signal is applied to the PLL voltage controlled oscillator to reduce the phase error output signal from the PLL phase detector to near zero volts and thereby improve the performance of the voltage controlled oscillator and the S/N ratio of the tuner. Various circuits are disclosed for deriving the above second DC control signal. Further improvement in the S/N ratio is effected by switching in a narrow capture range for the PLL circuit when the desired signal is received and when the PLL phase detector output is operated near zero volts. Also when the station is changed, detuning is detected to switch in a broader capture range.

Abstract: An intermodulation antiinterference circuit for a superheterodyne receiver having a receiving antenna comprising a first high frequency amplifying circuit responsive to the receiving antenna; a local oscillating circuit; a first frequency conversion circuit responsive to the first high frequency amplifying circuit and the local oscillating circuit; a variable attenuation circuit disposed between the receiving antenna and the first frequency conversion circuit; a nonlinear circuit responsive to the receiving antenna having less linearity than the first high frequency amplifying circuit; a second frequency conversion circuit responsive to the local oscillating circuit and the nonlinear circuit; a comparison circuit responsive to the first and second frequency conversion circuits for generating an output when the output of the second frequency conversion circuit is greater than the output of the first frequency conversion circuit; and means for changing the attenuation of the attenuating circuit.

Abstract: An oscillator suitable for use as a local oscillator of high frequency apparatus comprises a voltage controlled oscillator, a reference oscillator, a phase detector for detecting the phase difference between the oscillation frequencies of the voltage controlled oscillator and the reference oscillator, means for filtering the output of the phase detector to produce a DC voltage and a phase synchronizing loop for feeding back the DC output of the low-pass filter means to the voltage controlled oscillator. Depending upon whether the oscillation frequency of the reference oscillator is maintained at a duty cycle of 50% or at a value other than 50%, the oscillation frequency of the voltage controlled oscillator is synchronized with an odd multiple or an integer multiple of the oscillation frequency of the reference oscillator when the oscillation frequency of the voltage controlled oscillator is varied forcibly.