Scanning radio receiver

Claim 1

A signal-seeking receiver which automatically scans a plurality of channels of respective predetermined radio frequencies lying in at least three separated limited bands of frequencies and tunes to a received signal having a frequency corresponding to one of said channels, said receiver including an RF section for each of said bands, each such RF section having a mixer, signal-generating means for applying beating signals to respective ones of said mixers, a plurality of frequencydetermining crystals each corresponding to one of said predetermined frequencies, sequential switching means for automatically coupling successive ones of said frequencydetermining crystals sequentially to said signal-generating means to produce beating signals at respective frequencies beating with said predetermined frequencies to tune in the respective channels, band-switching means for activating respective RF sections, band selector means associated with each such crystal for operating said band-switching means to activate the RF section for the band containing the predetermined frequency corresponding to the respective crystal, detection means coupled to said mixers for producing information signals when a channel tuned in is being received, and inhibiting means responsive to said information signals for inhibiting said sequential switching means when a channel tuned in is being received and stopping the scanning on a receiving channel, said signal-generating means comprising an oscillator having a tuning circuit into which respective successive ones of said frequency-determining crystals are coupled and producing an oscillator output signal at a frequency determined by the respective crystal coupled into its tuning circuit, a first frequency-multiplying circuit coupled to said oscillator and responsive to said oscillator output signal for producing a first frequency-multiplied output signal at a multiple of the frequency of said oscillator output signals, a second frequency-multiplying circuit coupled to said first frequency-multiplying circuit and responsive to said first frequency-multiplied output signal for producing a second frequency-multiplied output signal at a multiple of the frequency of said first frequency-multiplied output signal, and applying means for applying said oscillator output signal, said first frequency-multiplied output signal and said second frequencymultiplied output signal respectively to respective ones of said mixers, at least one of said first and second frequencymultiplying circuits comprising an amplifier stage separate from said oscillator, saId receiver further including means for disabling said at least one of said frequency-multiplying circuits independently of said oscillator.