Electronic search tuning system

Claim 2

In a heterodyne receiving device having a voltage tuned radio frequency amplifier, a voltage tuned local oscillator, a first control circuit having an output which varies as a function of the magnitude of a received signal, and a second control circuit having an output which varies as a function of the frequency of an intermediate frequency signal within the receiver, an improved electronic search tuning system comprising: a first voltage source having an output which varies as a substantially linear function of time; means for selectively supplying the output of one of said first voltage source and said second control circuit to each of said radio frequency amplifier and said local oscillator; and means responsive to said first control circuit for controlling said selectively supplying means to supply the output of said first voltage source while the receiver is seeking an incoming signal and to supply the output of said second control circuit upon receipt of a sufficiently strong incoming signal.

Claim 3

In a heterodyne receiving device having a voltage tuned radio frequency amplifier, a voltage tuned local oscillator, a first control circuit having an output which varies as a function of the magnitude of a received signal, and a second control circuit having an output which varies as a function of the frequency of an intermediate frequency signal within the receiver, an improved electronic search tuning system comprising: a first voltage source having an output which varies as a substantially linear function of time; means for selectively supplying the output of one of said first voltage source and said second control circuit to each of said radio frequency amplifier and said local oscillator; and means responsive to said first control circuit for controlling said selectively supplying means to supply the output of said first voltage source while the receiver is seeking an incoming signal and to supply the output of said second control circuit upon receipt of a sufficiently strong incoming signal.

Claim 4

In a heterodyne receiving device having a voltage tuned radio frequency amplifier, a voltage tuned local oscillator, a first control circuit having an output which varies as a function of the magnitude of a received signal, and a second control circuit having an output which varies as a function of the frequency of an intermediate frequency signal within the receiver, an improved electronic search tuning system comprising: a first voltage source having an output which varies as a substantially linear function of time; means for selectively supplying the output of one of said first voltage source and said second control circuit to each of said radio frequency amplifier and said local oscillator; and means responsive to said first control circuit for controlling said selectively supplying means to supply the output of said first voltage source while the receiver is seeking an incoming signal and to supply the output of said second control circuit upon receipt of a sufficiently strong incoming signal.

Claim 5

The improvement of claim 1 wherein said first control circuit also functions as an automatic gain control circuit.

Claim 6

The improvement of claim 1 wherein said second control circuit also functions as an automatic frequency control circuit.

Claim 7

The improvement of claim 1 wherein said selectively supplying means comprises: a first transistor responsive to said first control circuit and adapted to be in a conducting state when said first control circuit indicates no sufficiently strong incoming signal to be present and in a nonconducting state when said first control circuit indicates the presence of an adequate incoming signal; and a second transistor responsive to the state of said first transistor.

Claim 8

The improvement of claim 4 wherein said second transistor is in a conducting state when said first transistor is in a nonconducting state and said second transistor is in a nonconducting state when said first transistor is in a conducting state.

Claim 9

The improvement of claim 4 further comprising a manually actuable means for switching said first transistor from its nonconducting to a conducting state in spite of the presence of an adequate incoming signal.

Claim 10

The improvement of claim 6 where said manually actuable means comprises a push button switch and a capacitor, said push button switch adapted to substantially alter the charge on said capacitor, said capacitor forming a portion of the biasing circuitry for said first transistor.

Claim 11

The improvement of claim 1 wherein said first voltage source comprises: a capacitance and a resistance connected in series across a direct current source, and means for rapidly changing the charge on said capacitance when the voltage thereon exceeds a predetermined value.

Claim 12

The improvement of claim 1 further comprising manually actuable deceiving means for temporarily substituting a different signal for the output of said second control circuit to effect manual tuning of the receiving device.

Claim 13

The improvement of claim 9 wherein said deceiving means superimposes a direct current bias on the output of said second control circuit.

Claim 14

A search tune circuit for a heterodyne receiving device having as inputs an automatic frequency control signal and an automatic gain control signal, and providing an output to at least one voltage variable capacitor diode comprising: a first transistor responsive to said automatic gain control signal and adapted to conduct when said automatic gain control signal indicates the receiver is not tuned to an adequate incoming signal and adapted to be nonconductive when said automatic gain control signal indicates the receiver is receiving an adequate incoming signal; means for amplifying said incoming automatic frequency control signal; a second transistor which is conductive when said first transistor is nonconductive and which is nonconductive when said first transistor is conducting; said second transistor adapted to provide when conducting a constant voltage output indicative of said incoming automatic frequency control signal; relaxation oscillator means adapted to provide a repeating substantially linearly changing with time output voltage when said second transistor is nonconductive; said second transistor effective upon changing from nonconduction to conduction to substitute for said linearly changing output voltage said automatic frequency control signal.

Claim 15

A search tune circuit for a heterodyne receiving device having as inputs an automatic frequency control signal and an automatic gain control signal, and providing an output to at least one voltage variable capacitor diode comprising: a first transistor responsive to said automatic gain control signal and adapted to conduct when said automatic gain control signal indicates the receiver is not tuned to an adequate incoming signal and adapted to be nonconductive when said automatic gain control signal indicates the receiver is receiving an adequate incoming signal; means for amplifying said incoming automatic frequency control signal; a second transistor which is conductive when said first transistor is nonconductive and which is nonconductive when said first transistor is conducting; said second transistor adapted to provide when conducting a constant voltage output indicative of said incoming automatic frequency control signal; relaxation oscillator means adapted to provide a repeating substantially linearly changing with time output voltage when said second transistor is nonconductive; said second transistor effective upon changing from nonconduction to conduction to substitute for said linearly changing output voltage said automatic frequency control signal.

Claim 16

The circuit of claim 11 further comprising a capacitor and a switch shunting the capacitor adapted to provide a bias voltage for said first transistor whereby said first transistor may be switched from its nonconducting to its conducting state upon actuation of said switch.