Investigation of Electromagnetic Wave Propagation in CB Radio with Elementary Students: A 'Super Bowl' Mystery

The Citizen's Band Radio Service (CB Radio), as defined by the United States Code of Federal Regulations, is a two-way voice communication service operating in the 27 MHz band, divided into 40 channels with a power limit of 4 Watts. Classified as High Frequency (HF), CB radio shares the spectrum with other services, and in Brazil, it offers similar functionalities with simplified registration. Motivated by the accessibility and low cost of equipment, elementary school students in Santa Catarina (-26.8668712, -49.2317786) conducted an experiment during lessons on electromagnetic waves. Using Aquarius RP40 and PRO401HH CB radios, the students received signals on channel 06 (27.025 MHz) in Amplitude Modulation (AM), identified as originating from the USA and related to the “Super Bowl” broadcast, through the analysis of the message content. After researching the possible source of the transmission, it was found that the signal travels approximately 7,850 km from its origin to the receiver, a distance estimated using geolocation tools and information from possible broadcasters found online, demonstrating the propagation of HF waves through the ionosphere. This region of the upper atmosphere reflects radio waves back to Earth, enabling long-distance communication through multiple “skips” between the ionospheric layers and the Earth’s surface. The observed variation in the received signal intensity, consistent with fluctuations in ionospheric electron density, highlights the influence of the ionosphere on signal propagation. Although long-distance reception may raise questions about transmission power, antennas, and other factors, this study emphasizes the role of the ionosphere, providing students with hands-on experience with radio communication equipment, deepening their understanding of electromagnetic waves through the ionospheric layer, and inspiring scientific inquiry.