W2du balun design pdf

Long the standard of the industry the w2au baluns are built to last. However, some of the companies who manufacture the w2du balun have come up short on the quality of their product, resulting in poor, and sometimes disastrous reports concerning. How the w2du ferrite bead balun originated it is interesting to know that the original design of the w2du ferrite bead balun is a spinoff from the development of antenna systems designed for spacecraft built by rcas astroelectronic division, specifically the antenna system developed by the author for. It is interesting to know that the original design of the w2du ferrite bead balun is a spinoff from the development of antenna systems designed for spacecraft. Dont believe anyone who claims to be an expert on baluns. Jerry sevick and are hand wound with best available components to provide highest possible efficiency. Design of low noise amplifiers using embedded passives 88 4. Walt was best known in the amateur radio realm for his groundbreaking series of articles, another look at reflections. A nonradiating balanced transmission line requires that the current in. The figure depicts typical lc bridge configuration. That means that nearly all of the i 2 current is radiated by the antenna, and none by the feed line. The w2du balun shown in attached photo is a lowpower version using 50 amidon fb732401 cores slipped over a 1foot length of rg58 coax. The main category is rf chokes that is about radio frequency chokes. Like ford vs holden, canon vs nikon or yaesu vs icom.

A brief report of some of the experimental data that led to the design of the commercial version of the w2du balun are shown in sec 21. The w2dus rf choke design can be used anywhere along your coaxial transmission path to help eliminate rf feedback and tvi. In essence it said, in this breakthrough article, w2dus peerless 1. The unadilla w2du hf maxibalun owes its extremely high power capability to the fact that it contains no ferrite cores to saturate. Locate a pill bottle or other nonconductive cylinder or piece of pvc pipe at least 3 in diameter. Basic balance quality test for current baluns a guanella or current baluns functional quality can be evaluated by moving a ground common with signal source to points a, b, and c figure 1 while watching voltages or currents in the load, or. While the rf currents flowing along the coax shield are choked out by the balunisolator, the internal 50 ohm signal is completely unaffected. Wireman model 827 balun is the w2du design available with so239 on one end of a pvc enclosure and 6 pigtails on the other end. I made no attempt to patent the device, and anyone can build it. If some of the greek characters dont come through ill have to repost with the material changed from word to pdf as an attachment, so here goes. Inline baluns provide similar performance to their respective wire balun counterparts.

It has little or no effect on i 1 and i 2 currents. The internal feed line passes through ferrite beads which prevent rf current from flowing on the coax shield. The peak amplitude of the signal is about 5 db below that of the balunfed antenna and one of the nulls, 30 degrees from broad side, is just as deep as was the null off the end of the balunfed antenna. In the professional literature as i noted in a recent cq artcie. Test, measure balun, and compare antenna baluns or balums. The balun device is used to balance inherently unbalanced systems by canceling or choking off unbalanced current flow.

I am the original designer of the w2du current balun, described in qst, march 1983. Examples are the ferrite bead balun described by walter maxwell, w2du, coiled up coax, and coax or a bifilar winding through a toroidal core. The maxwell bead balun has a useful peak common mode impedance from 160 through 15 meters. Resources listed under 1 to 1 balun category belongs to baluns main collection, and get. Current baluns are the balun of choice in all but very specialized situations, because they work better than voltage baluns in most realworld systems. An inexpensive, highperformance, ugly 50 ohm balun building a nogrief 1. While the rf currents flowing along the coax shield are choked out by the balun isolator, the internal 50 ohm signal is completely unaffected. The most common way balun design mistakes get into public domain is by improper or incomplete testing. Turn all the coils at the same time and connect them. The force 12 balun has a good peak common mode impedance from 40 meters to 10 meters. Join thousands of satisfied visitors who discovered antenna, rf circuit design and rf power. The balun has a long and illustrious history, first documented in the literature as a device to feed the television transmitting antenna for the empire state building1 in 1939. He measured 50, 100, and 200 bead chokes 200 beads best, 4x impedance of 50 beads much better noise suppression, better power handling commercial w2du balun only 50 beads or less w2dus beads are tiny.

The design is a variation of an order1 transmission line transformer described. The w2du maxibaluns owe their extremely high power capability to the fact that they contain no ferrite cores to saturate. A trick to identify the specific wire by making it a bit longer at both ends. Each has a builtin lightning arrestor, hang up hook, and 600 lbs. Rf balun calculator rf lc balun calculator and formula. The wire man also has w2du baluns available both in kit form and fully fabricated, ready for installation. This is actually a ferriteloaded coaxial rf choke which just happens to yield the same result as a 1. Balun designs established in 2005, balun designs builds exceptional quality baluns and ununs for amateur radio, military and commercial applications.

The diagram on the right shows what can happen if you dont include the balun. To properly match the 50 ohm coaxial cable to the feedpoint impedance the balun performs the 4to1 transformation 50 ohms 4 200 ohms and the opposite for receiving which converts the 200 ohms to 50 ohms. Of course, you may want to design your own but i just needed a nice balun for my portable ops. Following equation or formula is used for rf lc balun calculator. A nonradiating balanced transmission line requires that the current in the two conductors be the same. Even at high swr levels, the w2du balun will not generate harmonic radiation. Wideband balun design with ferrite cores senior project california polytechnic state university, san luis obispo paul biggins june 21, 2014. The w2du is the preferred balun of amateurs worldwide. The w2au is the preferred balun of amateurs worldwide. W2au baluns are transformer designs with ferrite cores to provide 95% minimum coupling efficiency. It is a choketype balun that consists of a number of small ferrite cores placed directly over a section of coaxial cable where it is connected to the antenna. Use a ferrite bar from a am receiver or better, a toroid. Windings are inserted into teflon tubes increasing total breakdown to 10,000 volts.

Some aspects of the balun problem by walter maxwell w2du rf. A balun or line isolator substantially reduces i 4 current. In all of the following, i will assume that the balun is a 1. The antenna pattern improves and most of the rf current flowing down the outer surface of the coaxs shield is eliminated. Walter maxwell, w2du, died july 3, 2012 at his home in deland, florida of natural causes. Chapter 21a how the w2du ferrite bead balun originated. Teflon type coax is used in this current balun surrounded by ferrite doughnuts.

This design is engineered by w2fmi to be 98% efficient which means little heat will be created inside the balun during operation. The w2du balun increases dramatically both the resistance and reactance for the. I believe this experiment shows at least to my satisfaction that the parasitic capacitancetoground effects of the 4191a, when measuring devices with a large amount of conductive surface area such as my 12turns of 12 awg wire inductor can greatly skew the impedance measurement, and that the s21 technique is a better way to go. A hams guide to rfi, ferrites, baluns, and audio interfacing. The internal feedline passes through ferrite beads which prevent rf current from flowing on the coax shield. Some aspects of the balun problem rf communication. Most of our units are derived from the researched and tested designs of dr. It is interesting to know that the original design of the w2du ferrite bead balun is a spinoff from the development of antenna systems designed for spacecraft built. This link is listed in our web site directory since sunday jul 27 2008, and till today a model of the w2du 1. The w2du s rf choke design can be used anywhere along your coaxial transmission path to help eliminate rf feedback and tvi. Order quantities of 4 or more units may increase production time. This led me to an investigation of just how baluns are supposed to. Applications for inline baluns include line isolation anywhere along the coax transmission system and use on quad and yagi antennas. Newer and inferior designs w2dus design is 50 years old thats old fashioned certainly something newer must be better.

Since then designs have evolved dramatically, and applications have evolved beyond driving differential antennas to include balanced mixers, amplifiers, and signaling lines of all types. There are a couple of points about this trace that need to be considered. I had to strip the outer cover of the coax off so that the beads would fit over the coax. The balun is a transmission line transformer tlt some baluns are narrowband because they depend on a section of transmission line that is a.