The microwave online drier is constructed as a tunnel containing modules
consisting of 5 applicators (cavity, waveguide and magnetron) placed side by side.
Each such cavity has a length of approximately 0.44 metres and a width of 0.31
metres. The number of cavities determines the possible length of the wood
components, in this case 2.2 metres. The magnetrons, or microwave generators,
have a nominal maximum output power of 1 kW, and the power for each
magnetron can be regulated continuously [35]. The possible wood load thickness
can be chosen from 15 to 55 mm. Since the tunnel is open at both ends, chokes are
placed in the end openings to eliminate microwave radiation leakage. The
modules in this design are manufactured to have a parallel displacement of 35 mm
between each other (figure 20) to prevent the hotter regions formed in the material
(figure 19) from appearing at the same positions in the wood load as they are
conveyed through the tunnel during the drying process. The size of the
displacement depends on the wavelength. The hotter regions are formed with a
distance of a half wavelength, and for that reason the displacement is a quarter
wavelength.