###### Abstract
This article aimed to characterize the soil itself, to study underground communication, and to examine the propagation characteristics of electromagnetic waves in the soil, considering factors such as moisture content, temperature, general geological structure, and the frequency of the incident electromagnetic radiation. This characterization plays a pivotal role in determining the dielectric constant. Measuring complex dielectric properties has gained significant interest in precision agriculture, particularly as applied to Wireless Underground Sensor Networks (WUSNs). The dielectric constant is a critical parameter that characterizes the behavior of the soil. The electromagnetic properties of the soil significantly influence the performance of underground penetration and the propagation of waves that transmit and collect data through the soil. When the transmitted signal reaches the soil, it propagates back toward the surface. Factors such as temperature, salinity, and mineral content affect connectivity and communication success. The waves experience attenuation, due to the high density and complex mixture of minerals, water, air, and organic matter in the soil. Many agronomic and hydrological studies rely on precise measurements of soil dielectric permittivity. Current systems use sensors based on reflectometry, a diagnostic method where a signal is sent into the medium being assessed. This signal propagates according to established laws, and part of its energy is reflected when it encounters an impedance mismatch. The reflected signal (reflection coefficient) can provide valuable information about the system. In regard to achieving our goals, numerous studies have shown that MHz frequency bands can effectively operate for underground communications, employing techniques such as Time Domain Reflectometry (TDR) or Frequency Domain Reflectometry (FDR) [11; 12; 13]. These techniques offer precise instrumentation for estimating the complex dielectric permittivity of various soil types. Other probes commonly used in TDR and FDR agriculture serve to calculate the complex dielectric permittivity of different soil types. It is important to note that the current measurement methods do not fully meet the technological demands of the market. The limitations stem from the high costs associated with TDR and the need for calibration in FDR systems. Therefore, there is a need for better calibration than current FDR sensors provide, as well as a more affordable solution, compared to the available TDR meters. Consequently, applying FDR sensors in the 433 MHz frequency range appears promising, particularly for achieving a more universal calibration than existing FDR sensors and at a lower cost than current TDR meters. This article presents the design of an underground probe that addresses the challenges of underground channel communications. It represents an initial step toward developing an efficient prototype for measuring dielectric soil permittivity in a Wireless Sensor Network. The proposed probe measures complex dielectric permittivity at a frequency of 433 MHz, suitable for low-power transceivers such as those using LoRa technology. This paper is organized into several sections. The first part, titled \"Introduction\", presents the context and objectives of the study. Next, the \"Materials and Methods\" section describes the materials used and the experimental methods employed to conduct the research. The third part, \"Results and Discussion\", presents the findings and analyzes them in comparison to the existing literature. Finally, the \"Conclusions\" section summarizes the key insights from the study and suggests directions for future research.