Tech Articles

Unfortunately there is no industry standard for measurement of power ratings for baluns and ununs.  Consequently, 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 set our own company standards and what follows is provided for a better understanding of the installation and best use of our units. Research and testing by Dr. Jerry Sevick PhD (W2FMI sk) determined the follo …

Selecting the best toroid material or "mix" for baluns and ununs.Transmitting balunsOccasionally errors are made regarding core selection and this especially includes baluns, where on occasion 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 (pr …

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 …

Most matching problems occur when the antenna system presents an extremely high impedance to the tuner. An antenna system should be considered everything from the tuner to the tip of the antenna. High impedance feedline is usually considered that which has over 300 ohms impedance and are typically are 300 ohms, 450 ohms and 600 ohms in impedance. When the antenna impedance is much lower than the feedline impedance, an odd quarter-wavelength feedline converts the low antenna impedance to a v …