Measurements and analysis suggest why quarter-wave stubs fail to completely isolate radiator conductors on multi-band antennas including the popular rollup 2m/440 J-Pole products. Possible improvements are shown.
Tame the predictable mast currents found in any j-pole antenna grounding conductive mast using a simple stub. Shown is empirical evidence why this is a problem and a very simple solution all future grounded j-pole antennas should incorporate.
The traditional collinear J-Pole, aka Super-J, improves the basic J-Pole. Are further improvements possible? By replacing the phasing stub with a simple coil, the answer is yes. The result is the Collinear J-Pole.
The Northern Virginia team of Ham Radio operators and companion hikers manned Hawksbill Mountain for the 2011 Appalachian Trail Golden Packet event. Gear included a Kenwood D710 with Green Light Lab GPS, 2m Collinear J-Pole and a 70cm collinear J-Pole.
We remove the mystique surrounding the 5/4 wave antenna comparing center and end fed approaches. One conclusion is the end fed 5/4 wave antenna shows little promise as a vertical antenna for terrestrial use.