Tech Articles

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 …

Matching Problems using a tuner and high impedance feedlineMost 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-w …

We occasionally receive emails from customers who feel their balun is defective because they are unable to replicate our test results. This is due in large part to the effect of stray capacitance picked up by the testing method they use.  Below you will see a pictorial review of how our testing is performed and the methods used to eliminate the effect of stray capacitance.  We also show a scan using a non inductive 50 ohm resistor with wire leads and the magnitude of error this typical …

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 …