Design and Implementation of a Low-Cost 2.4 GHz RF Activity Monitoring System using ESP32 and nRF24L01

Krishnakumar R, Aadhil Rehman P A, Rahman A, Vinod N, Jissmi K

The rapid proliferation of wireless communication devices has resulted in increasing radio-frequency (RF) activity within the 2.4 GHz Industrial, Scientific, and Medical (ISM) band. Wireless technologies such as Wi-Fi, Bluetooth, ZigBee, and numerous Internet of Things (IoT) devices coexist within this frequency region, creating a need for simple and economical methods of observing RF activity. Conventional spectrum analyzers provide accurate frequency-domain measurements but are often expensive for educational and low-cost embedded applications. This paper presents the design and implementation of a compact 2.4 GHz RF activity monitoring system using an ESP32 microcontroller and an nRF24L01 transceiver. The proposed system sequentially monitors RF channels supported by the transceiver and utilizes its Received Power Detector (RPD) functionality to identify the presence of RF energy above the internal detection threshold. The ESP32 controls the scanning operation, processes the channel activity information, and displays the observed results on an SSD1306 OLED display. An LM2596-based power regulation stage and local de-coupling components are employed to support stable operation of the RF module. Experimental operation demonstrates the ability of the developed prototype to observe variations in RF activity and provide standalone real-time visualization. The proposed system offers an economical platform for basic spectrum awareness, educational experiments, and introductory investigation of wireless activity in the 2.4 GHz ISM band.