This article has shed some light upon typical problems of the oscillator design. A number of additional signals can be excited by the oscillator's active kernel due to parasitic effects. These interfere with the projected oscillation frequency or with its harmonics and produce a number of disturbing spurious signals. By the help of a suitable CAD program, such as C/NL2, it is possible to avoid this problem. The CAD program can analyze the reason for these additional oscillations and comfortably give advice how to take measures to inhibit the oscillator's circuit capability to produce these unwanted additional parasitic oscillations. This article examined the problem of exciting spurious emission in an oscillator circuit and proves, that an oscillator can be easily CAD designed and assembled, producing the designed frequency signal, only.