## 2 Materials and Methods  
To explore and validate the feasibility of utilizing Unmanned Aerial Vehicles (UAVs) as telecommunication base stations for monitoring, data acquisition, and analysis, the problem was segmented into three primary tasks, each with several subtasks:  
1. Selection of electromagnetic radiation measurement equipment: 1. Identification and/or development of suitable spectrum analyzers, filters, and antennas for installation on UAVs; 2. Development of control software tailored to the selected equipment; 3. Implementation of a multi-frequency data transmission channel to mitigate interference risks during diverse measurements. 2. Design and adaptation of UAV platforms: 1. Selection or design of rotary-wing and fixed-wing UAV platforms capable of accommodating the chosen equipment; 2. Modification of UAVs for safe landing in populated areas; 3. Adjustment of autopilot software to fulfill the specialized requirements; 4. Selection of multi-frequency telemetry and control data transmission channels to minimize interference with measurement equipment. 3. Integration of UAVs and measurement systems: 1. Integration of measurement equipment, particularly antennas, within UAV structures; 2. Compatibility assessment and testing of UAV systems, data transmission systems, and measurement systems; 3. Development of measurement methodologies; 4. Experimental validation of integrated systems. This structured approach facilitated systematic exploration and validation of UAV-based telecommunication base stations, ensuring thorough consideration of equipment selection, platform adaptation, and system integration. The general measurement system diagram is presented in Figure 1:Regarding the mentioned tasks and the general measurement diagram in Figure 1, radio frequencies recorded by the spectrum analyzer were transmitted to the onboard measurement computer, which also controlled the spectrum analyzer via a USB connection. Measurement data and control signals were transmitted from the aircraft via onboard dedicated communication equipment to the ground station, where they were displayed on a remote-control computer (ground station). The total weight of the measurement system when assembled was in the range of 2 kg. The entire measurement system located on the aircraft was integrated into a box (Figure 2a). After conducting measurements and testing (by analytical and experimental methods comparing metal and composite boxes), it was concluded that the most suitable option for the specific application would be an aluminum box, ensuring low radio interference, mechanical protection, and sufficient cooling of system components. The measuring equipment was installed in the aircraft, designed, and mounted in such a way that it could be easily mounted both in a multi-rotor and in a fixed-wing aircraft, or even used completely separately as ground-based measuring equipment. In addition, a new measurement data processing algorithm and new recording software were developed. During the investigation and development, a few versions of the multi-rotor drones (Figure 3a) and a fixed-wing UAV were developed, as shown in Figure 3b, for conducting measurements, carrying the same equipment as the aforementioned experimental one. Figure 1: General measurement system diagram. Figure 3: (**a**) The measurement equipment is mounted in a hexacopter. (**b**) The measurement equipment is mounted (experimentally) in a fixed-wing aircraft. Figure 2: (**a**) Measurement system equipment. (**b**) Measurement system equipment mounted in a specialized box. (**c**) Measurement system box. (**d**) Measurement system box with a specialized antenna. In all cases of investigation and during measurements, aircraft coordinates were determined using the RTK (Real-Time Kinematics) GNSS system, ensuring 1-2 cm accuracy in aircraft position. An experimental multi-rotor aircraft during flight is shown in Figure 4b.