Tech Articles

How a 1:1 Guanella-Balun (Current-Balun) Operates By Jerry Sodus, KM3K In the spirit of the hobby, I pass along what I have learned and don’t profess to know all the answers. 1. The primary reason for this work is to explain how a particular Transmission-Line-Transformer (TLT) known as a 1:1 Guanella-balun operates. Three other commonly used names to describe this balun are: “current-balun”, “isolation-balun”, and “choke-balun”; I’d suggest committing all four names to memory. The 1:1 Guane …

Currently there is no industry standard for measurement of power ratings for baluns and ununs.  Because of the many different types of ferrites, build methods and levels of quality, comparison of the same type of balun/unun from different vendors can have very different outcomes when the unit is put in to service.  With this in mind, we have established our own standards based on the research and testing of Dr. Jerry Sevick PhD (W2FMI sk).  Dr Sevick is well known for his numerou …

Selecting the best toroid material or "mix" for baluns and ununs. Transmitting baluns Occasionally errors are made regarding core selection and this especially includes baluns, where some very strange ideas surface. One rather odd but somewhat popular idea is that adding a mixture of core types will allow both high power operation and high choking impedance in baluns by slowly reducing current through a balun. Other misleading claims are that extreme values of core ui (pronounced mu), such …

This is a partial reprint (with permission) of an excellent series of articles published by KV5R on shortwave antennas. His full series can be found at www.KV5R.com As previously stated, a ½ wave antenna radiates off of the sides, perpendicular to the wire. Longwire antennas radiate toward the far end of the wire. Let’s look at what happens to the directivity pattern of our 94-foot wire. As we dial up the frequency, the pattern of the antenna changes. The following diagrams show r …

Reprinted with permission of Hamuniverse, this is an excellent explanation of SWR and how to best measure it.What is SWR?SWR or Standing Wave Ratio is one of the most misunderstood terms in amateur radio. Even though every antenna and transmission line book that I have seen is quick to point that out, it still is the source of many misconceptions. To most hams with an SWR meter, SWR is whatever the meter reads and if the meter says there's no problem, then all is well. That simply isn't true. In …