There is a need in a practical scenario for ion heating up to high temperatures in a mirror based neutron source. Such a scenario could be developed with the ion cyclotron heating. Fundamental harmonic ion cyclotron heating of deuterium and second harmonic heating for tritium are studied numerically from the point of view of antenna coupling and heating efficiency. The behavior of the antenna loading resistance and radio-frequency power shine-through the cyclotron zone with the heating frequency, plasma density and temperature and the antenna position is analyzed.