Rf Signal Generator Circuit
This circuit uses a VFO operating from 15 to 18 MHz (Ul), which feeds a balanced mixer (U2). A fixed oscillator signal is mixed with this signal to generate an output from 0.4 to 33 MHz. FL1 and FL2 are low- and high-pass filters that are used to eliminate undesired mixer products.
Amplifier U3/Q3 supplies up to 200 mV rms to the output jack.