Centaur Baluns are the "state of the art" in balancing an unbalanced (Coax) line to a balanced feed (antenna, ladder line, etc.). There are two kinds of Centaur products for your balun needs:
B11W10-50 1:1 Dipole balun matches 50 ohm coax with balanced (of equal length) wires cut to the proper frequency. SRP $99.95
B41LW10-50 4:1 Ladder Line balun matches 50 ohm coax to 200 ohm or 450 ohm ladder line and then to a wire antenna cut to the proper length for frequency. SRP $129.95
Why are bigger baluns better than smaller baluns?
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