Wire Span
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Dipole length and VSWR

Example matched 50 ohm load

Return loss is not finite when gamma is zero.

Worked example

Each legEach leg10.189 m10.189 mTotal span20.379 m

Total length 20.3786 m

Each leg 10.1893 m

L_feet = 468 / f. L_meters = 142.65 / f. Leg feet = 234 / f. Leg meters = 71.325 / f.

These lengths are a formula starting point. They are not a guaranteed cut length. End effect, insulation, and height are not in the equation.

VSWR

Conditions: load 50 ohm, reference 50 ohm. Real values only. Length is not used.

Gamma is 0, so the formula calls this a complete match. Return loss is not finite. This is not a measured match and not a guaranteed build.

Gamma 0

Gamma = (Z_L - Z_0) / (Z_L + Z_0)

VSWR 1

VSWR = (1 + |Gamma|) / (1 - |Gamma|)

Return loss is not finite because |Gamma| is 0.

Reflected power 0 %

P_refl = |Gamma|^2 * 100

Notes only: about 73 ohms at 180 degrees, about 58 at 120, about 50 at 90. Not interpolated.