Antenna Length Calculator
Enter a frequency above and click Calculate to see antenna dimensions.
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Common Operating Frequencies β Click to Calculate
160m Phone
1.900 MHz
80m Phone
3.750 MHz
80m FT8
3.573 MHz
40m FT8
7.074 MHz
40m Phone
7.200 MHz
30m FT8
10.136 MHz
20m FT8
14.074 MHz
20m Phone
14.225 MHz
15m FT8
21.074 MHz
15m Phone
21.300 MHz
10m FT8
28.074 MHz
10m Phone
28.500 MHz
6m Phone
50.125 MHz
2m SSB
144.200 MHz
2m Simplex
146.520 MHz
70cm SSB
432.100 MHz
Antenna Building Tips
Cut Long, Trim ShortAlways cut wire 3β5% longer than calculated, then trim to resonance with an antenna analyzer. You can always remove wire; you can't add it back.
Velocity FactorBare copper wire in free air: use 0.95β0.97. Insulated wire runs slightly shorter due to the dielectric effect of the insulation β use 0.92β0.95.
Height MattersDipole height above ground affects feedpoint impedance and radiation angle. At Ξ»/2 height, impedance approaches the theoretical 73Ξ©. Lower heights raise impedance and lower the radiation angle.
EFHW TipAn EFHW for 40m (66 ft) is also resonant on 20m, 15m, and 10m. Pair with a 49:1 unun at the feed point. Counterpoise wire of 0.05Ξ» helps feedline common-mode rejection.
Inverted-V ShapeBending a dipole into an inverted-V shape (apex at top, ends angled down 30β45Β°) slightly lowers the resonant frequency β expect to trim about 3% from the calculated length.
Quarter-Wave VerticalA quarter-wave vertical needs a ground radial system β at least 4 radials of Ξ»/4 length for reasonable efficiency. More radials = lower ground loss = better performance.
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