Calculate dimensions for a J-Pole antenna based on operating frequency.
Antenna Parameters
MHz
Calculated Dimensions
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Quick Reference
AThree-quarter wave radiator
BQuarter-wave matching stub
CFeed point (from bottom)
DSpacing between elements
Overview
A J-Pole antenna is an end-fed omnidirectional half-wave antenna that uses a quarter-wave matching stub. It's popular for VHF and UHF amateur radio due to its simple construction and high performance without needing a ground plane.
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Pro Tips
The velocity factor depends on the material (copper tubing is usually around 0.95-0.96).
Mount the antenna at least half a wavelength away from metal objects.
The feed point (C) may need slight adjustment to reach the minimum SWR (Standing Wave Ratio).
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Fun Facts
"The J-Pole antenna was originally invented by Hans J. Zinke in 1936."
"It doesn't require a ground plane or radials, making it very portable."
"The bottom section acts as a balanced matching transformer, while the top part acts as the radiator."
