The TEM cell placed inside an incubator (37°C, 95% humidity and 5% CO2) was a 3 mm copper box of 19.25 x 20 x 50 cm with a tapered horizontal copperseptum dividing the inner space into two equal parts. To allow gaseous exchange between the incubator and the cell cultures, one side of TEM wall was made of a 2.5-mm size copper-mesh. The geometry and field propagation have been well described in literature [Stuchly and Stuchly, 1996]. The electric field was perpendicular to the septum plane.
The magnetic and electric field in the TEM cell were measured using a spectrum analyser equipped with a 1-cm magnetic loop or a 3-cm electrospherical probe. Detected values matched the theoretically expected values within the systematic error range. A directional coupler, an RF detector, and a scalar meter with a CRT display were used to optimise and continuously check the input return loss of the TEM cell. Properly adjusted, the system measured a return loss of 27 dB with and without the Petri dishes inside resulting in a field uniformity of better than 2 dB.