SUPER_SIMPLE_SHORTWAVE_RECEIVER

Published:2009/6/17 22:31:00 Author:May | From:SeekIC

Integrated circuit U1 (an NE602 double-balanced mixer) is a combination oscillator and frequency mixer. Signals from the antenna input (at J1) are fed through dc-blocking capacitor C1 to the RF-gain control, R1, and fed to the input of U1 at pins 1 and 2.The local-oscillator frequency, which varies with the settings of R2 and L2, is mixed internally within U1, resulting in an output. The ntixer output at pin 4 of U1 is applied to a tunable 260-kHz band-pass intermediate-frequency (IF) transformer, L3, through dc-blocking capacitor C7. There-fore, signals that are roughly 260 kHz above and below the local-oscillator frequency are passed while others are effectively blocked. The IF frequencies are now amplified by Q2 and Q3. The AM au-dio signal is detected by D2 and its associated components, which bypass the RE signals, and leave only the audio signals. The signals are preamplified by U1-a (half of an LM358 dual op amp). The audio is then boosted to speaker level by the LM386low-voltage audio power amplifier, U3.



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