June 18, 2016 1259 am lagunacomputer. So it seems that when the antenna fell down, it broke the solder on my horizontal radials that are connected to the ground. Mhz Yagi Antenna Build your own antenna for the 23cm band 1250Mhz 1280Mc using some aluminium and this simple design. In this pictorial Im showing you how to make a 16dBi very powerful wifi antenna for under 10 dollars. Ive already posted a movie about this but a lot of people. Yes, the house wiring can be the problem. Powerline sends the signal over the house wiring. In theory that is OK, the receiver can then extract the signal. Can you use a pipe cutter or a hack saw, can you solder then here is how to build a SIMPLE J antenna that will more than double your 2 meter and even 440. One of the most popular variations of this practice is known as the Pringles can antenna, or cantenna for short, which utilizes both a waveguide probe design. Over the Air TV or OTA TV signals allow you to watch HDTV for free. This guide explains what to consider when buying an OTA digital TV antenna. Build Yagi Antenna Wifi Receiver' title='Build Yagi Antenna Wifi Receiver' />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. 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. Best Hack Slash Games 2009 Chevy here. 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. 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.