Microwave nondestructive testing of light red meranti timber

Microwave nondestructive testing techniques were used for measuring moisture content and slope-of-grain of light red meranti timber. Reflection and transmission measurements were performed on a free-space microwave measurement set up in the frequency range of 8 to 12.5 Ghz. Free-space set up consists of two spot-focusing horn lens antennas, waveguide transitions, coaxial cables and a microwave vector network analyzer. Errors due to diffraction effects at the edges of the specimen is minimized because of far-field focusing ability of antennas and multiple reflections between antennas are eliminated by using a free-space LRL (line, reflect and line) calibration technique. Slope-of-grain will be deduced from copolarized and crosspolarized reflection and transmission measurements on 15 cm by 15 cm by 2.5 cm light red meranti timber specimens. Moisture content was evaluated from measured complex permittivities of dry and wet timber specimens.