![]() ![]() This collection of notes makes a start-but by no means a finish-of the task. The availability of an inexpensive but quite adequate antenna analyzer, the AIM 4170, has not only eased the task of making at least some preliminary measurements, but doing so very accurately. However, I have not seen a report on the precision with which various available balun designs actually transform the load impedance to the target input impedance across the intended use range, namely, the HF spectrum from 3 to 30 MHz. There have been numerous reports in amateur literature on the power capabilities of available balun designs and commercial as well as homebrew implementations of them. ![]() 2 shows some sample tuner configurations, all of which share in common the 4:1 output balun. ![]() To obtain a balanced output-or at least an output in which neither output terminal is connected to ground-designers have long used a 4:1 balun between the network and the connections for a parallel transmission line. In many instances, the ATU employs a single-ended network against a ground that is also common to the case. They transform an actual 200- antenna feedpoint impedance value to a match for the 50- main feedline.Ī number of radio amateurs do run parallel transmission line from their multi-band wire antennas to an antenna-tuning unit (ATU). A few amateurs actually install a 4:1 balun under optimal conditions. Parallel transmission line runs from the balun's balanced output terminals to the antenna feedpoint, while coaxial cable does indoor duties. ![]() Alternatively, some amateurs install the 4:1 balun at the entry point to the equipment building. Some amateurs install 4:1 baluns at the feedpoint of multi-band antennas in the mistaken belief that the input impedance may be compatible with the standard 50- coaxial cable. 1 presents only two of numerous scenarios. Despite the specifications, amateurs employ (or misemploy) 4:1 baluns in a number of circumstances in which the device has little hope of matching its output to the actual load. The normal design frequency range is (more commonly) 3.5-30 MHz or (less commonly) 1.8-30 MHz. Theoretically, these devices are designed to transform a 200- load impedance value to a 50- input impedance level. One of the most ubiquitous antenna-system accessories among radio amateurs is the 4:1 balun. File Info : application/pdf, 52 Pages, 1.87MB Document Document TheImpedance-transformationPropertiesOfCommon4to1BalunTypes The Impedance-Transformation Properties of Common 4:1 Balun Types Part 1: Essential Background ![]()
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