Balun table.

Calculate windings on a Balun

Impedance (Ohms)  :1
VoltageV :1
CurrentA :1
Primary windings (range):   - Step


Enter a value in one of the fields.

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The table is presented in a new window (or tab) after pressing the "Calculate table" button.

A voltage BalUn (Balanced / Unbalanced) transformer can be used to match antennas to feed lines and is commonly used for amateur radio (HAM) rigs, predominantly for center-fed antennas.

For the impedance factor 4, two stranded wire can be wound around a ferrite (or other) core (such as a toroid).
One line can be both primary and half of the secondary.
The secondary is balanced and can be created by combining both wires that are connected together and to the ground.
Note that one secondary side is directly connected to the input.

For the (default) impedance factor 6, two lines can be combined in a similar manner (as the balun described above).
Extra windings that are part of the secondary, are added on the ends of the primary part of the same line - an auto-transformer.

Other impedances can be matched in a similar manner within some practical limitations.

Note that the values displayed in these calculations are overly accurate and theoretical without regard for the wire lead in, capacitance or losses.

Note that the error is the actual secondary compared to the ideal secondary and includes the extra windings on both sides of the voltage balun autotransformer.
The error is expressed as absolute total extra windings (Abs), Voltage percentage (%[V])and Impedance (Ohms) percentage (%[Ω]).
Impedance mismatch (and its reflected power) is expressed as VSWR (SWR - standing wave ratio).

The "One extra" entry shows what exactly one complete winding too many (on each end) would look like as a "worst-case" scenario to show how the error gradually decreases with more windings.

Disclaimer: Intended for my own personal theoretical calculations and not verified or tested.


See sample table below:

6:1 Balun table

Impedance matching Balun:   6:1 Ω    (2.44949:1 V,   0.408248:1 A)



Windings Extra windings on each side of doubled primary
Primary Secondary Extra Nearest Whole Nearest Half One extra
Extra error refl Extra error refl error refl
Abs %[V] %[Ω] SWR Abs %[V] %[Ω] SWR %[V] %[Ω] SWR
9.5 23.27015 2.135 2 -0.27 -1.16 -2.31 1.02 2.5 0.73 3.14 6.37 1.06 8.59 17.93 1.18
10 24.4949 2.247 2 -0.49 -2.02 -4 1.04 2.5 0.51 2.06 4.17 1.04 8.16 17 1.17
10.5 25.71964 2.36 2 -0.72 -2.8 -5.52 1.06 2.5 0.28 1.09 2.19 1.02 7.78 16.16 1.16
11 26.94439 2.472 2 -0.94 -3.5 -6.89 1.07 2.5 0.06 0.21 0.41 1 7.42 15.4 1.15


See also: Links, Home. KJ6RGW Written by:   Frans B. Simon van Leeuwen.