Unlock optimal performance for your amateur radio setup with our J-Pole Antenna Calculator. Quickly determine precise dimensions for your desired VHF or UHF frequency, ensuring an efficient and easy-to-build antenna. Ideal for hams, this tool simplifies complex calculations for custom antenna projects.
Formula:
The J-Pole antenna calculator uses the following formulas, accounting for a velocity factor (VF) typical of copper pipe or wire antennas:
- Radiator Length (L1, 1/2 λ) = (142.6 / F) × VF (meters)
- Stub Length (L2, 1/4 λ) = (71.3 / F) × VF (meters)
Where:
- F = Desired Frequency in Megahertz (MHz)
- VF = Velocity Factor (e.g., 0.95 for typical wire, 0.96 for copper pipe)
Note: The feed point (L3) is typically 10-15% of the stub length (L2) from the bottom shorting bar, and element spacing (S) is usually between 2.5-5 cm (1-2 inches) for common designs. These aspects are often fine-tuned empirically.