Electromagnetic waves in metal tubes of rectangular cross-section

The attenuation of electromagnetic waves propagated through the interior of metal tubes of rectangular cross-section is calculated by the familiar telephone transmission formulae, the top and bottom of the tube being regarded as zigzag flat-strip transmission lines while the side walls are regarded, when suitably disposed, as transmission lines of another type. From the losses occurring in these lines, the attenuation offered by the tube is obtained in a simple manner. The results are found to be in agreement with those established by more elaborate means by other investigators. The characteristic advantage of the method here described is its simplicity and the directness with which the final results emerge. The method also provides a link between electrical communication through the interior of hollow metal tubes and the transmission of waves along telegraph and telephone lines of conventional type.