  Being a general wave phenomenon, bound states in the continuum (BICs) appear
in acoustic, hydrodynamic, and photonic systems of various dimensionalities.
Here, we report the first experimental observation of an accidental
electromagnetic BIC in a one-dimensional periodic chain of coaxial ceramic
disks. We show that the accidental BIC manifests itself as a narrow peak in the
transmission spectra of the chain placed between two loop antennas. We
demonstrate a linear growth of the radiative quality factor of the BICs with
the number of disks that is well-described with a tight-binding model. We
estimate the number of the disks when the radiation losses become negligible in
comparison to material absorption and, therefore, the chain can be considered
practically as infinite. The presented analysis is supported by near-field
measurements of the BIC profile. The obtained results provide useful guidelines
for practical implementations of structures with BICs opening new horizons for
the development of radio-frequency and optical metadevices.

Classical Physics;Optics