Here are some details on how to construct a simple Balun. The first one changes your 50 Ohm Unbalanced output from your transmitter to match 200 ohms balanced to your balanced feeders antenna. It is not critical. The antenna may have 450 Ohm open wire ladder line. The output of the 50 ohm to 200 ohm balun will work just fine and so will your antenna.

The second balun is a simple 50 ohm unbalanced to 50 ohm balanced lines and is quite useful when the antenna has a low impedance unbalanced feeder feeding a length of coaxial line. The balun may be incorporated into the centre insulator of a dipole and will eliminate stray RF currents flowing back down the outside coaxial braid into your shack

A 50 ohm unbalanced to 200 ohm balanced balun and
A 50 ohm unbalanced to 50 ohm balanced balun

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Two No. 14 wire gauge wires around an Amidon T63 Ferrite Core