Tech Articles

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 …

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. For example, 3 pF of stray capacitance represents a reactance of about 1.7K ohm at 30MHz which will appear to be in parallel with the load. This will seriously affect readings at higher frequencies if the capacitance is not properly eliminated. …

With the advent of new technology in TV's, power supplies/chargers, new lighting products and other modern devices, there is an unfortunate downside from the electronic noise many of these items generate. To that end, we receive numerous emails and calls seeking a remedy to the ever increasing noise floor in our receivers. No question that baluns are one of the answers, but they are not the sole answer and in some cases are not the answer at all. To better understand this statement it is import …

As with most equipment, we have become accustomed to determining our needs relative to power handling capability and the output power being used. However, when it comes to baluns and ununs, this rating or capability should not be used as a primary decision maker. The reasons for this are many and varied but here are a few of the most important.When a balun or unun is wound correctly, which is an important differentiator, a higher power rating will also mean a higher efficiency, low SWR and exc …