Author(s)

Ma Yuqi ¹

Affiliation(s)

¹ Suzhou High School of Jiangsu Province, Jiangsu, Suzhou, 215007, China

Corresponding Author

Ma Yuqi

ABSTRACT

A crystal radio provides a compact passive platform for examining how weak radio-frequency energy is captured, selected, rectified and converted into audible sound without external amplification. Focusing on the frequency selection mechanism of the receiver, the analysis links antenna coupling, LC resonance, quality factor, detector loading and adjacent-channel rejection within a single signal path. The resonant frequency is determined by the inductance-capacitance combination, while the actual tuning response is reshaped by coil resistance, stray capacitance, diode conduction and earphone impedance. Calculated LC data and load-condition comparison show that higher quality factors narrow the passband and strengthen station separation, whereas heavier detector or audio loading increases damping and reduces selectivity. The results indicate that the performance of a crystal radio depends on a careful balance between signal strength and resonance sharpness. Practical improvement should focus on low-loss coil construction, stable variable capacitance, controlled antenna coupling, low-threshold detection and high-impedance audio loading, so that passive reception can maintain sufficient sensitivity while preserving clear frequency discrimination.

KEYWORDS

Crystal radio; Frequency selection; LC resonance; Quality factor; Detector loading

CITE THIS PAPER

Ma Yuqi. Physical Principles and Performance Analysis of the Frequency Selection Mechanism in Crystal Radios. Modern Physical Chemistry Research (2026) Vol. 6, No.1, 15-20. DOI: http://dx.doi.org/10.23977/mpcr.2026.060103.

REFERENCES

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