The ubiquitous interconnectivity of electronic devices offered by Internet-of-Things (IoT) networks has been increasingly embraced in a wide range of applications. In IoT networks, threats to hardware security are often not perceived as serious, with the assumption that an attack could only be carried out at close proximity. However, in this article, we show that through electromagnetic (EM) side-channel signal leakage, operational information and program activities of IoT devices and field-programmable gate array (FPGA) modules can be garnered from approximately 200 m away in an outdoor line-of-sight (LOS) environment. We describe an extensive measurement campaign conducted to investigate the aforementioned leakage and provide propagation models that can be used to predict the power (and corresponding variation i.e., shadowing gain) of the EM side-channel signal emanation at various distances, scenarios, and environments. With a circularly polarized receiver antenna, our results show that the received power of the emanated EM side-channel (carrier) signal varies from about -61 dBm at 1 m to about -112 dBm at 200 m in the outdoor LOS environment. Furthermore, a received signal power of about -73 dBm was observed at 1 m and -88 dBm was recorded at 10 m in an indoor LOS environment. Power variation (shadowing gain) of about 3.6 and 2.0 dB was observed in the outdoor and indoor environments, respectively. This work is relevant for EM side-channel leakage countermeasure development and provides pertinent information to embedded systems and wireless network security engineers.