BALUNs and UNUNs

Our BALUNs, UNUNs, and EFHW transformers cover antennas from 1.8 to 450 MHz — broadband units spanning most of the HF spectrum, and single-band units tuned for exceptional performance over a narrow range. Our 1:1 baluns are current-type designs, wound and measured in-house for maximum resistive choking impedance across your operating band, because current balance is what keeps common-mode current off your feedline. Learn why in About BALUNs.

Which one do you need?

1:1 BALUN (50:50) — for coax-fed dipoles and Yagis, plus a tuner balun for ladder-line antennas. Provides current balance at the feed point and stops feedline radiation. The default choice for a standard 50-ohm balanced antenna.

4:1 BALUN (200:50) — for off-center-fed (OCF) dipoles, horizontal loops, and other balanced antennas with a feed-point impedance near 200 ohms. For loops and OCF dipoles, the BL-154V-3K is a deliberate Ruthroff-style 4:1 voltage design, used with a CMC choke on the feedline.

9:1 / 4:1 UNUN — for non-resonant random-wire and vertical antennas, such as 27 ft or 43 ft wires, fed against a ground or radial system. See EFLW vs. EFHW for how they differ from an end-fed half-wave.

EFHW transformers (49:1 / 56:1 / 75:1 / 81:1) — the matching transformers for end-fed half-wave antennas. Note these are UNUNs, not baluns — see All About EFHW Antennas.

The rule of thumb: balanced antenna near 50 ohms → 1:1 BALUN; balanced antenna or loop near 200 ohms → 4:1 BALUN; non-resonant wire or vertical → UNUN; end-fed half-wave → EFHW transformer. When in doubt, ask — I answer the technical questions personally.