Radio receiver with field intensity detector

Claim 1

A radio receiver having a field intensity detector, comprising: at least one intermediate frequency amplifier means having a gain that is incrementally variable in predetermined step amounts and is supplied with an intermediate frequency input signal; frequency discriminator means for demodulating an output of said intermediate frequency amplifier means; field intensity detector means supplied with an output of the intermediate frequency amplifier means for producing a dc voltage, said dc voltage having a level corresponding to the input level; control means responsive to the output signal levels of said detector means for producing a "0" or "1" control signal depending upon whether the level of said output dc voltage of the field intensity detector does or does not raise above a predetermined level; output terminal means on the radio receiver for providing the control signal and the output dc voltage of the field intensity detector means; and means responsive to said control signal for selectively changing the gain of the intermediate frequency amplifier means by a selected step amount in order to vary the gain thereof in a step-wise manner in response to said control signal; said control means comprising a comparator responsive to the field intensity detector means detecting a range of input field intensities for producing an output with a hysteresis characteristic having a dynamic range corresponding to said detected range; said intermediate frequency amplifier means being constructed to decrease or increase the gain which corresponds to an amount of a range of input field intensities which are detectable by the field intensity detector means.