Abstract
This study presents a compact navigation electronic seal system employing the Iridium SBD9603 radio modem and a specialized antenna for transmitting Short Burst Data (SBD) messages. The primary objective was to integrate a satellite antenna within the constrained space of the device enclosure. Due to the impossibility of the manufacturer-recommended horizontal antenna placement, the antenna was installed at a 70° angle. Experimental results confirmed the feasibility of this configuration. In open-space conditions, a stable signal level sufficient for communication was observed 88.6% of the time, while inside a protective enclosure made of PA12 + GF composite material, this value decreased to 65.3%. The average data packet delivery time ranged from 8 to 14 s. These results are explained by the dielectric properties of the enclosure material and partial signal shielding. At the same time, short-term signal fading (on average up to 43 s) was considered acceptable, since a typical SBD transaction takes less than 10 s, allowing efficient use of message retransmission. An important finding of the study is that when the seal is mounted on a steel container door, the inclined antenna performs more efficiently than the horizontal configuration (65.3% versus 61.1%). This effect is attributed to the metallic surface acting as a reflective screen, optimizing the electromagnetic conditions for the inclined antenna aperture. The obtained results can be applied in remote monitoring and identification systems for cargo transported in containers and trucks, including operation under challenging environmental conditions.