The J-Pole antenna employs a half-wavelength radiator fed by a quarter-wave matching stub. The antenna is an end fed dipole that has an omni directional pattern and a low angle of radiation  The J-Pole employs a quarter wave stub matching transformer that provides a means of transforming the high impedance of the antenna to that of the lower impedance of the transmission line. Average gain with this J Pole is about 3 db. The J-pole radiates from the top 1/2 wave length of the antenna.  Yet another advantage of the J-Pole is that it is at DC ground; so it can be mounted just about anywhere and still work. Because the antenna is at D.C. ground, it has less noise making it better a better antenna if lighting is in the area, and making it a ground rod by taking the lightning to ground as long as it is mounted on a grounded mast of some sort. This antenna  is also broad banded and offers low VSWR (Voltage Standing Wave Ratio) across the operating range.  Because it it is an end fed Dipole it does  not require a ground plain.

This antenna works well and I have used it several times with a full 50 watts on  2 meters and have used it for UHF.  It does not work as well as a single band UHF but it does work and also has low VSWR across the UHF band.