Dipole Antenna Calculator
Calculate half-wave dipole total and per-leg lengths from frequency using the standard 468 formula.
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What this tool does
Calculate half-wave dipole total and per-leg lengths from frequency using the standard 468 formula. For thin wire elements in typical installations. Height above ground, nearby objects and element diameter shift the exact resonant length — trim on the air.
How to use the Dipole Antenna Calculator
- Enter or select frequency (mhz).
- Read the calculated result; change any measurement to compare alternatives.
Formula
total length (ft) = 468 ÷ f (MHz); each leg = total ÷ 2
- frequency
- Frequency (MHz)
For thin wire elements in typical installations. Height above ground, nearby objects and element diameter shift the exact resonant length — trim on the air.
Worked example
For dipole antenna calculator, the following measurements illustrate the exact method: Frequency (MHz): 146.
Inputs
- Frequency (MHz)146
Result
- Total dipole length (ft)3.21
- Each leg length (ft)1.6
- Total length (m)0.98
- Each leg length (in)19.23
Results explained
- Total dipole length (ft)
- Total dipole length (ft) from the formula above. For thin wire elements in typical installations. Height above ground, nearby objects and element diameter shift the exact resonant length — trim on the air.
- Each leg length (ft)
- Each leg length (ft) from the formula above. For thin wire elements in typical installations. Height above ground, nearby objects and element diameter shift the exact resonant length — trim on the air.
- Total length (m)
- Total length (m) from the formula above. For thin wire elements in typical installations. Height above ground, nearby objects and element diameter shift the exact resonant length — trim on the air.
- Each leg length (in)
- Each leg length (in) from the formula above. For thin wire elements in typical installations. Height above ground, nearby objects and element diameter shift the exact resonant length — trim on the air.
Frequently asked questions
Total length in feet ≈ 468 ÷ frequency in MHz — the classic formula already includes the roughly 5% end-effect shortening from the free-space value 492 ÷ f. At 146 MHz that is about 3.21 ft total.
A wire antenna resonates slightly shorter than the free-space half wavelength because of end capacitance and the wire's velocity factor; 468 is the long-established practical constant for wire dipoles in feet.
Half the total — cut each element to a quarter wavelength (234 ÷ f in feet), then trim symmetrically for the lowest SWR at your feedpoint.
Slightly: thicker elements and insulated wire shift resonance a little and widen bandwidth. Cut long and trim, measuring with an antenna analyser or SWR meter.
A centre-fed dipole in free space is about 73 Ω; mounted near ground at typical heights it usually lands near 50–70 Ω, a good match for 50 Ω coax.