Dual-Band VHF UHF J-Pole Antenna Construction

This resource provides construction details and performance data for a dual-band J-pole antenna designed for 2-meter and 70-cm operation. The antenna utilizes TV twin lead and coaxial cable, with a total length of approximately 52 inches. Performance metrics include a measured SWR of 1.7:1 or better across most of the 2-meter band and less than 2:1 across the 70-cm band. All SWR data was measured at the transmitter end of the feed line, referenced to 50 ohm impedance. The document details the theoretical basis of the J-pole, including calculations for the quarte-wavelength radiator and quaeter-wavelength stub based on velocity factor and design frequency. An example design frequency of 146 MHz is provided for the 2-meter band. The ARRL article focuses on practical construction and measured results for a specific antenna type.