The invention relates to an HF system that comprises an HF device (5), particularly an HF lamp, as well an HF spark-plug or similar HF plasma application, and an HF signal-incoupling device (3) for operating said HF device (5). The HF system comprises an oscillator (7) for generating an HF signal to operate said HF device (5), and said system is characterised in that it comprises means (15) for generating a voltage signal (Uprop) that is proportional to the degree of adaptation of the HF device, on the basis of the HF signal generated by the oscillator (7) and a signal reflected by said HF device. Moreover, the system is characterised in that it comprises a device (27), preferably without a microprocessor, for generating a control signal (UA) for adapting the oscillator (7) output-frequency on the basis of the voltage signal (Uprop) which is proportional to the degree of adaptation of the HF device (5).