View Full Version : antenna capacity hats

05-19-2021, 08:04 PM
an article on the do-dads on top of some antennas .


teaser ..... "Cap hats are not new innovations, and have been used in one form or another almost since the dawn of radio. The first patent covering them (US patent #609,154) was issued to Sir Oliver Joseph Lodge, a British physicist, in 1898. His abstract of the patent reads in part, "...As charged surfaces... I prefer, for the purpose of combining low resistance with great electrostatic capacity, cones or triangles or other such diverging surfaces with the vertices adjoining and their larger areas spreading out into space..."

The reason he chose the design was to reduce the Q of the antenna system, thus increasing its bandwidth. Based on his comments from the patent, he also realized that the input impedance would increase, and the overall length at resonance would decrease! This is exactly what cap hats do, if installed correctly!"