Real-Time Galactic Neutral HydrogenSignalsHI Detection: “Probing the 1.42GHz, 21-cmLine” with Fabricated Conical HornRadioAstronomy Telescope

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The study presents the detection of galactic neutral hydrogen (HI) signals at the 1.42 GHz frequency, corresponding to the 21-cm spectral line, using a fabricated conical horn antenna installing at Beijing University of Posts and Telecommunications(BUPT) with the aid of educational purposes for radio astronomy applications. The 21-cm line arises from the hyperfine transition in neutral hydrogen and serves as a key tracer of the interstellar medium (ISM), enabling studies of galactic structure, dynamics, and large-scale distribution. The antenna was designed with a 60°conical geometry and constructed using a copper, most common of antennas, low-cost and high conductivity (perfect electric conductor) model to ensure high gain and efficient impedance matching at the target frequency. The real-time experimental setup, including a spectrum analyzer and preamplifier, was optimized to detect the weak emissions from hydrogen gas in the Milky Way. Measurements yielded a signal strength of-87.48 dBm as received power and a realized gain of 11 dB, demonstrating the antenna's sensitivity and effectiveness in isolating the 21-cm emission line. The results validate the potential of this compact and low-cost horn antenna design for galactic HI weak signal observations. The study contributes to the development of accessible radio astronomy instrumentation and provides a platform for future enhancements, including low-noise amplification and sky-mapping applications, in the ongoing exploration of neutral hydrogen in the universe.