| 摘要 |
A manual tuning circuit for an AM and/or FM radio (10) in which the magnitude of the radio audible signals is intentionally varied in accordance with the magnitude of an error signal related to the absolute difference between the frequency of a desired received modulated carrier signal and the frequency to which the radio front end (11-17) is tuned. In this manner, precisely tuning the radio front end to precisely the desired frequency can be obtained by tuning for the maximum volume of radio audible signals. Preferably, this is accomplished through the use of full wave rectification of either the FM discriminator (35) DC output voltage or full wave rectification of the control voltage for a voltage controlled oscillator (VCO) (26) in a phase locked loop (24) which tracks the IF output signal of an AM/FM radio IF stage (16). |
