The current paper presents the experimental study of the frequency-modulated chaos shift keying (FM-CSK) communication system. The proposed system has the potential to enhance the security aspects of the physical layer to meet the needs for safe data transmission in wireless sensor networks (WSN). Compared to common digital FM-DCSK, the studied analog FM-CSK communication system provides a more straightforward design. As chaos oscillators are the core elements of the FM-CSK communication system, the paper investigates the selected oscillators’ properties, including the implementation aspects—the impact of reactive element value deviations on dynamics and synchronization stability. Chaotic dynamics are evaluated with the mean-square-displacement-based 0–1 test, while correlation analysis is used to evaluate synchronization. The impact of the different chaos oscillators’ employment on FM-CSK communication system performance is examined, and the bit error ratio is used for noise immunity evaluation.