The propagation of electromagnetic waves in a circular tunnel being studied, as far as his walls are made of concrete, its conductivity coefficient would be in the range 10
^{-1}
–10
^{-2}
mho/m. The cutoff frequency was also calculated and three different types of frequency range were characterized. Each of the frequency range is characterized, in turn, by certain propagation modes which differ in the cases of transverse electric modes (TE
_{mn}
– modes) and transverse magnetic modes (TM
_{mn}
– modes), (m, n = 0, 1). Besides, the attenuation constant was calculated at values larger and smaller than that of the cutoff frequency for both the transverse electric waves and transverse magnetic waves. Numerical results and graphes are also given for different values of m and n (m, n = 0 or 1) and a range of selected frequencies between 20–300 MHz.
