Plural band scanning radio with direct switch of RF amplifying transistors

Claim 1

In a stepping radio receiver for production of audio signals from radio frequency signals and capable of tuning to several separate channels on a plurality of bands, which radio receiver includes: (a) a pre-IF section having an RF signal-receiving means, mixing means, and an oscillator means; (b) said pre-IF section being operable on a plurality of distinctive bands; (c) a power supply having a first and second common supply lead; (d) said RF signal-receiving means being for providing sufficient RF signal level for said mixing means; (e) said mixing means being coupled to the RF signal receiving means; (f) an audio detection means coupled to said mixer means for producing an audio signal when an RF signal is being received, said audio detection means including squelch means for preventing the production of an audio signal when an RF signal is not being received; (g) said oscillator means being coupled to said mixer means and operable at a given several frequencies, there being one frequency for each channel to which the receiver can tune; (h) stepping means which is defeatable and which has several outputs which are coupled to said oscillator means for stepping said oscillator means through said given several frequencies; (i) locking means which is connected to the stepping means for defeating said stepping means as long as an RF signal is being received and allowing resumption of operation of said stepping means when no signal is being received; (j) a programmable band-selecting means connected to the pre-IF section of the receiver and to the stepping means for determining the band of operation of the receiver; (k) said programmable band-selecting means including a plurality of enabling means, each enabling means being for enabling operation on one of the bands; the improvement which comprises: (l) said pre-IF section including a plurality of switchable transistor amplifiers which amplify pre-IF, RF signals, there being at least one of said switchable transistor amplifiers associated with each band; (m) said stepping means having means for producing a low impedance to said first common supply lead for the output which is "ON" and a high impedance or voltage with respect to said first common supply lead for the outputs which are "OFF", and (n) means connected with said programmable band-selecting means for providing a current path for one of said switchable transistor amplifiers which passes through the low impedance output of said stepping means, the selection of said one of said switchable transistor amplifiers being made by said programmable band-selecting means, said current path having the same current through both the stepping means outputs and said switchable transistor amplifiers.