RF Baluns for Ham Radio Antennas

 A balun is a device that interfaces a balanced antenna with an unbalanced coaxial cable feedline. The word "balun" is a contraction of "balanced to unbalanced." Without a balun, the coaxial cable becomes part of your antenna system in ways you never intended. Common mode current flows down the outside of the coax shield, distorting your antenna's radiation pattern, increasing RFI into your shack, and raising your receive noise floor. A good balun stops that from happening — keeping RF where it belongs and your antenna performing the way it was designed. 

 There are two fundamentally different types of baluns, and choosing the wrong one for your antenna is a common and costly mistake. A voltage balun forces equal and opposite voltages on each leg of the antenna — but makes no guarantee about current balance. A current balun, also known as a choke balun, forces equal and opposite currents in each leg of the antenna, which is what actually determines radiation pattern and common mode current suppression. For most ham radio antennas — especially dipoles and yagis with feed point impedances near 50 ohms — a current balun is the correct choice. 

 The right balun depends on two things: your antenna's feed point impedance and how well balanced it naturally is. A 1:1 current balun is ideal for dipoles, yagis, and other antennas with feed point impedances near 50 ohms. A 4:1 balun is designed for antennas with feed point impedances near 200 ohms — such as loops, folded dipoles, and off center fed dipoles (OCFDs). Getting the impedance ratio wrong means your feedline sees a significant mismatch, which increases SWR and reduces power transfer to your antenna. 

 Off center fed dipoles are inherently unbalanced antennas — and that makes them one of the most challenging antenna types to feed correctly. A standard 4:1 voltage balun will match the impedance, but it does a poor job of balancing current in each leg of the antenna because voltage balance and current balance are not the same thing. The result is elevated common mode current, a distorted radiation pattern, and RFI in your shack. A hybrid balun — combining a voltage balun with a current balun in series — solves this problem by balancing both voltage and current simultaneously. For OCFD operators, this is not a luxury, it's a necessity. 

Every Watts Engineering Labs balun is built to handle the full HF spectrum from 1.8 to 30 MHz with exceptionally low loss. Our 1:1 Current Balun exhibits less than 0.09 dB of loss — completely undetectable on transmit or receive. Our 4:1 Hybrid Balun adds less than 0.12 dB across the entire HF band. These are not theoretical figures — they are measured values from fully characterized units, just like any professional RF component should be. Every balun is sealed for outdoor use and can be mounted in any orientation, with multiple mounting options to suit any installation.