The modified j-pole: A wideband end-fed half-wave dipole for a VHF reflector feed system

A “J-pole” is a 3λ/4-long dipole-type antenna that can be end-fed and does not require a ground plane or radials. This paper describes a modification to the classical J-pole which reduces the length to about λ/2. While this results in directivity about 0.5 dB less than an ideal half-wave dipole, the fractional bandwidth is increased to about 40% for |s
₁₁
<; -10 dB (50Ω). The use of this antenna as part of a new supplementary VHF-band feed system for an existing reflector antenna is described.