An experimental study of attenuation per unit length in a cylindrical slot line

Attenuation per unit length in slot lines with vacuum-sprayed aluminum and brazed silver coatings was measured in the range 25-35 GHz with an accuracy of plus or minus 30 percent. An attenuation of 0.09 dB/cm has been measured in silver-brazed slot lines, whereas attenuation losses in aluminum-sprayed lines have been found to be as high as 1.2 dB/cm. It is shown that ohmic losses in the conducting coating account for the largest part of total losses in the lines. The losses can be reduced by depositing a dense uniform film on the dielectric.