Damped Electromagnetic Waves in Hollow Metal Pipes

Simple apparatus for the production of damped waves in hollow-pipe wave guides is described. The results of some measurements at free-space wavelengths down to 4.59 centimeters in circular air-filled pipes as small as 2.86 centimeters in diameter show that such apparatus can be successfully employed for the investigation of the properties of hollow-pipe waves. Some data are given which confirm part of a previous theoretical analysis of the behavior of electromagnetic waves in a pipe of elliptical cross section, and a possible method of detecting small deformations in a supposedly circular pipe is discussed.