A clapp oscillator is in effect a series tuned version of the colpitts oscillator. Perhaps the simplest Colpitts oscillator to construct and get running is the "series tuned" version, more often referred to as the "Clapp Oscillator". Because there is no load on the inductor a high "Q" circuit results with a high L/C ratio and of course much less circulating current. This aids drift reduction. Because larger inductances are required, stray inductances do not have as much impact as perhaps in other circuits.

A clapp oscillator is in effect a series tuned version of the colpitts oscillator. Perhaps the simplest Colpitts oscillator to construct and get running is the "series tuned" version, more often referred to as the "Clapp Oscillator". Because there is no load on the inductor a high "Q" circuit results with a high L/C ratio and of course much less circulating current. This aids drift reduction in what is otherwise a clapp oscillator. Because larger inductances are required, stray inductances do not have as much impact as perhaps in other circuits.

Figure 1 - schematic of a series tuned colpitts or "clapp" oscillator

For greater details of this circuit and its values see the tutorial on colpitts oscillators