Posted on May 22, 2012

This is a 3-W, single-circuit board, VFO-controlled CW transceiver for 40 or 30 meters, featuring a direct-conversion receiver with audio filtering, Receiver Incremental Tuning (RIT), and speaker level audio volume. The transmit frequency is generated by Ql and its associated components in tbe VFO. The buffer, Q2, isolates the oscillator from the other circuitry to help keep the VFO stable. Q3 builds up tbe signal to a more usable level. The driver, Q4, amplifies the signal. The final, Q5, amplifies it to the 3-W level.

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Key tbe transmitter by turning the power to tbe driver on and off, using Q6 as a switching transistor. Select tbe frequency by varying tbe tuning capacitor, C2. The VFO frequency feeds into the diode-ring mixer, and is mixed with the incoming 7-or 10-MHz signal. The difference, or produce, is the audio frequency. The post-mixer circuitry amplifies tbe audio signal to speaker level: Q8 preamplifies the signal a little, U2 is an audio filter tbat attenuates the audio signals above about 700Hz, and U3 amplifies tbe signal from the audio filter to listening level.

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