We have investigated experinrentally resonance excitationand the damping mechanism of high-frequency oscillations ofa plasma cylinder that isin an external magnetic field. Wave excitation was accomplished with a system of external coils creating a spatially periodical electromagnetic field with a period λ0 = 15 cm. The operating frequency.(f = 10 MHz) wasconsiderably smaller than theelectron cyclotron frequency (ω ≈ ωHe/200) and greater than theioncyclotron frequency.It has been shown that the oscillations penetrate well into the plasma. The wavelength measured along the direction of the magnetic field λz coincides with the period of the exciting coil λ0 and corresponds to the length of the wave that is defined from the dispersion ratio for these oscillations. The direction of the rotation of the wave coincides with the direction of the rotation of the electron in a magnetic field.The measured damping length of the wave was l = 40cm. Plasma density of n0 ≈ 5 × 1013 ions/cm3, electron temperature was Te ≈ 50 eV, and the wave length in the damping region was λz = 10 cm. Wave damping length due to collisions was lst ≈ λz ωHe/2πν (ν is the frequency of collisions between electrons and ions) of the order of 104 cm, which exceeds the value measured by more than a hundred times. Damping length due to the collisionless Cerenkov mechanism is lL≈(λz/2π)2(m/Te)1/2ωHe = 60 cm, which compares well with the value measured. On these grounds the conclusion is drawn that the observed damping is caused by the collisionless Cerenkov mechanism.