Correspondents have informed me that the balun dealt with in article 4:1 current balun – review and fix and variants are very common. This article gives a checklist of common issues and some basic measurements using an antenna analyser that should reveal some issues without breaking into a sealed assembly.
Introduction
Baluns are commonly employed to obtain nearly balanced feed line currents (ie negligible common mode current) in two wire lines or negligible common mode current on coaxial feed lines. This article discusses baluns for that application.
A very common 4:1 current balun is Guanella’s 4:1 current balun, but there are others including pretenders.
Three common 4:1 current baluns
Guanella 4:1 current balun
(Guanella 1944) described a 4:1 current balun in his 1944 article, he did not show the winding pairs coupled by a magnetic core as shown above.
Above is Guanella’s circuit, and he does not show coupling between the two winding pairs.
Properly implemented, this device is known to work very well.
Sevick’s single core 4:1 current balun
Let us look at Sevick’s device because it underlies so many failures.
If you look at it very carefully, you will see that the two output wires emerge from opposite sides of the core, the left hand wire exiting under the core was wound from front to back of the core and the right hand wire exiting on top of the core was wound from back to front of the core. Continue reading 4:1 current balun – identifying bad ones
