On Point The Yagi Antenna. If you happened to look up during a drive down a suburban street in the US anytime during the 6. TV antennas. When over the air TV was the only option, people went to great lengths to haul in signals, with antennas of sometimes massive proportions flying over rooftops. Outdoor antennas all but disappeared over the last third of the 2. But now cheapskates cable cutters like yours truly are starting to regrow that once thick forest, this time lofting antennas to receive digital programming over the air. Many of the new antennas make outrageous claims about performance or tout that theyre designed specifically for HDTV. Amateur Radio, Antenna Theory, Homebrew Antennas, Hidden and Stealth Antennas, CCRs, and Antenna restriction. Acknowledgements. Yagi Calculator is a program to assist with the design of long yagi antennas. It uses the graphs and principles developed by DL6WU and printed. CONTENTS. 1. Design Information 2. Computer Modeling 3. Element and Boom Corrections 4. Practical Construction. End, Back. A good Yagi design is as easy to build as a. Programs to design some of the most common types of antennas and a some experimental antenna designs. Youll need to cut two pieces of PVC pipe. One piece will be 17 12. The other 7. This, along with the PVC connectors, will form the frame of the antenna. This antenna will extend the range of your WiFi or 2. GHz devices like surveillance cameras into many miles and kilometers. A yagi antenna is basically a teles. METER SSB YAGI PLANS FOR SIDEBAND FUN This 6 element beam was designed using the free Yagi Antenna Design program by WA7RAI called Quick Yagi QY4. A 2 Meter and 70 CM Portable Tape Measure Beam Work the OSCAR ham satellites or go transmitter hunting with this inexpensive portable dual band handheld tape measure. Its all marketing nonsense, of course, because then as now, almost every TV antenna is just some form of the classic Yagi design. The physics of this antenna are fascinating, as is the story of how the antenna was invented. Uda WhoShintaro Uda. Source IEEE Cincinnati Section. What would come to be known as the Yagi antenna got its start in the early 1. Professor Shintaro Uda in the Tohoku Imperial University in Sendai Japan. Dr. Uda was working in the VHF band and was looking for ways to make antennas more directional. While experimenting with a resonant loop antenna, he discovered that placing a static loop near the antenna tended to shape the signal away from an omnidirectional pattern, almost as if the loop was acting as a reflector. Together with his colleague Hidetsugu Yagi, Uda experimented with different configurations. They eventually replaced the loop antenna with a simple dipole, and added additional elements, which they called directors, on a long boom to further shape the beam. Using eight directors on a 1. Uda and Yagi were able to communicate over a distance of 1. MHz, no mean feat at the time. Hidetsugu Yagi and his antenna. Source Physics World. Having dubbed their invention the wave projector directional antenna, it was inevitable that the antenna would be named after someone. How it came to be credited solely to Dr. Yagi is a tale of some treachery on Yagis part with a dash of naivet on Udas. Dr. Uda published the first Japanese language papers on the antenna, but for reasons unknown, Dr. Yagi applied for both Japanese and American patents for the antenna with no mention of Uda. The Japanese patent was assigned to the Marconi Company in England, while the American patent went to RCA. With no mention of Uda, and with Dr. Yagi touring the English speaking world to discuss his antenna at various radio engineering conferences, the antenna gradually became simply the Yagi antenna or the Yagi array. Ironically, thanks to inter service rivalries and a silo mentality in Imperial Japan, it was only the capture of a British radar set during the Battle of Singapore in 1. Japanese military. The Japanese intelligence officers didnt even consider Yagi to be a Japanese name they supposed it was just a code word made up by the British. Parasites. The chief characteristics of the Yagi Uda antenna are high directionality and high gain. Given the fact that the length of each element needs to be close to some fraction of the wavelength of the signal, its most practical for the higher frequencies, mostly above 3. MHz. Thats not to say that it cant be used for the longer wavelengths, though plenty of hams work the 2. Yagi. A Yagi for the ham bands. Note the driven element with feedline, seven directors, and a single reflector. Source Antenna Theory. As in Dr. Udas original design, a Yagi consists of a single driven element parallel to and coplanar with at least two parasitic elements. A minimal design is a single reflector element located behind the driven element relative to the direction of the radio signal and a single director element in front of the driven element. A practical antenna is likely to have multiple directors, the more of which there are the tighter the directionality and the higher the gain, at least up to a point. This gives Yagis their characteristic appearance a horizontal boom with multiple elements arranged perpendicularly. There are some variations, of course some Yagis have multiple reflectors, or have a corner reflector arrangement. And some antennas, particularly TV antennas, have the parasitic elements swept back at an angle rather than perpendicular to the boom. Additionally, the elements can be arranged horizontally or vertically, depending on the polarization desired. Phasing. To understand the Yagis design, recall that a plain old dipole antenna in free space has a radiation pattern that is the strongest broadside to the antenna. That results in two big lobes off the front and the back of the antenna, with little signal off the ends. The driven element of a Yagi is just a half wave dipole, or sometimes a folded dipole to increase the impedance. The parasitic elements shape and direct the beam using constructive and destructive interference. As Dr. Uda discovered, the parasitic elements can either be inductively or capacitively coupled to the driven element. Inductive elements are slightly longer than half wave, while capacitive elements are slightly shorter. The directors are all shorter than half wave and are therefore capacitively coupled, while the reflector is longer and inductively coupled. The difference from the ideal half wave is small usually only 1. Constructive and destructive interference in a Yagi antenna. The green wave represents the sum of the red and blue waves. Source Radar. Tutorial. Both the reflector and the directors work by reradiating power from the driven element. The spacing of the parasitic elements relative to the driven element determines the phase of the reradiated signal. The reflector, being inductively reactive, reradiates power 1. The spacing is set so that this causes destructive interference off the back of the antenna, while at the same time being nearly in phase with the driven signal off the front of the antenna. This results in constructive interference, boosting the power off the front. Similarly, the capacitively coupled directors are spaced so that they reradiate power more or less in phase in the forward direction, while radiating out of phase to the rear. The result is greatly amplified signal toward the directors, and almost none behind the reflector. And recall that antenna theory states that any antenna that transmits can also receive, and with the same characteristics. It doesnt matter whether the driven element in a Yagi is driven by a 1. TV tower. The directionality and gain will be the same. Day Of Doom Epub. And Yagis can have remarkable gain up to 2. Bm when correctly designed. As useful as the Yagi antenna is, its far from perfect. Because of the critical size and spacing of the parasitic elements, Yagis have a relatively narrow bandwidth. Also, the directionality of the antenna can be an inconvenience, requiring that the antenna be rotated to point more or less exactly at the transmitter or receiver. But if you need to pull in a single distant signal, that directionality is just what you need. The Yagi is a workhorse antenna, and given the impact it has had its probably right and good that many have taken to referring to it as the Yagi Uda antenna. YAGI ANTENNA DESIGN BASICS. BASIC YAGI ANTENNA DESIGN FOR THE. EXPERIMENTERHelpful. Yagi Antenna Design. How to Understand basic Yagis. Condensed and re edited from various. This. article is not designed to give you construction details for building a. Yagi. It is designed to give you a better basic understanding of how the. Yagi is designed and the basic functions of each of its. GENERAL. DESCRIPTION OF A YAGIThe word Yagi is used to. Japanese antenna experts by the names. Yagi and Uda Most hams refer to this type of antenna as the. Yagi rather than use both mens. They discovered that by adding elementsof various lengths. The Yagi antennas overall basic. These parasitic. elements are called the reflectorand the directors. The reflector. The. Yagi is called the. From experimentation, they determined that the effect. They also. learned that by changing the space between the elements, and the. They found that they. THE. ELEMENTS OF A YAGITHE DRIVEN ELEMENTThe driven element of a Yagi is the feed point. Yagi to. perform the transfer of power from the transmitter to the. A dipole driven element will be resonant when its electrical. The feed point in the picture above is on the center of the. THE DIRECTORThe directors is the shortest of. Yagi is aimed at the receiving. It is resonant slightly higher in frequency than the driven. The directors lengths can vary, depending upon the. The number of directors. The directors are used to. The amount of gain is directly proportional to the length of. The. spacing of the directors can range from. THE REFLECTORThe reflector is the element that is. The dipole. Its resonant. Its length will vary depending on the spacing and the. The spacing of the reflector will be between. Its spacing will depend upon the gain. FB ratio, and sidelobe pattern requirements of the final. BANDWIDTH AND IMPEDANCEThe impedance of an. Of. primary importance here is the impedance of the driven element, the point. Maximum energy transfer of rf at the design. In most antenna designs, the feedline. Yagi is rarely 5. In most cases it can vary from approximately 4. If the feedline. impedance does not equal the feed point impedance, the driven element. Standing Wave Ratio. Because of this, impedance matching devices are highly recommended for. The impedance bandwidth of the. The design goal is. Yagi 0,. j 0. The impedance matching device will now operate at its optimum. Wide element spacing, large element diameter, wide pattern. Q matching systems will all add to a wider impedance. ABOUT ANTENNA PATTERNSThe. Yagi antenna. The. The antennas. radiation pattern bandwidth is the range of frequencies above and below. The. amount of variation from the antennas design specification goals that can.