Two gates, U1A and U1B O/3 of a 4049 hex inveter), are connected in a VFO circuit. Components Rl, R3, and CI set the frequ
ency range of the VFO. With the values given, the circuit"s output can range from a few hundred hertz to over several thousand hertz by adjusting R3. The simplest way to change the frequency range of the oscillator is to use different capacitance values for CI. A rotary switch, teamed up with a number of capacitors, can be used to select the desired frequency range.