yagi-uda

7 Articles

Pocketable Yagi Antenna Really Shoots For Distance

November 2, 2023 by 45 Comments

For amateur radio operators, the quest for the perfect antenna never seems to end. Perhaps that’s because our requirements are always changing. We never quite seem to get to one design that can do everything. This copper-foil Yagi antenna might not do everything, but it really seems to tick off the boxes for gain and directionality along with ultra-portability.

If you’ve been following [Ben Eadie (VE6SFX)]’s trip down the rabbit hole of lightweight antenna building, you’ll recall that he’s already knocked off a J-pole antenna and a stealthy mobile slot antenna using little more than copper foil tape. Both of those designs performed great, but [Ben] had bigger fish to fry: he wanted to build a directional antenna for the 2-meter band and go for distance. The traditional Yagi-Uda is generally the preferred design for beam antennas, but they tend to be bulky and cumbersome. But with a roll of copper foil tape [Ben] was able to lay out a three-element Yagi on a sheet of Tyvek wrap. Reinforced with some packing tape and stiffened with a couple of fiberglass rods attached to a 3D printed handle, and it was ready to go.

[Ben]’s field test results were most impressive. Not only was he able to open up repeaters up to 90 km away, but he was getting good signal reports to boot. He was even able to reach a repeater 150 km distant, just barely though. Still, that’s mighty impressive performance from something that looks like a Union Jack and rolls up to fit in a pocket.

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Printing Antennas On Circuit Boards

April 6, 2023 by 19 Comments

Yagi-Uda antennas, or simply “Yagis”, are directional antennas that focus radio waves to increase gain, meaning that the radio waves can travel further in that direction for a given transmitter power. Anyone might recognize an old TV antenna on a roof that uses this type of antenna, but they can be used to increase the gain of an antenna at any frequency. This one is designed to operate within the frequencies allotted to WiFi and as a result is so small that the entire antenna can be printed directly on a PCB.

The antenna consists of what is effectively a dipole antenna, sandwiched in between a reflector and three directors. The reflector and directors are passive elements in that they interact with the radio wave to focus it in a specific direction, but the only thing actually powered is the dipole in the middle. It looks almost like a short circuit at first but thanks to the high frequencies involved in this band, will still function like any other dipole antenna would. [IMSAI Guy], who created the video linked above which goes over these details also analyzed the performance of this antenna and found it to be fairly impressive as a WiFi antenna, but he did make a few changes to the board for some other minor improvements in performance.

The creator of these antennas, [WA5VJB] aka [Kent Britain] is an antenna builder based in Texas who has developed a few unique styles of antennas produced in non-traditional ways. Besides this small Yagi, there are other microwave antennas available for direction-finding, some wide-band antennas, and log-periodic antennas that look similar to Yagi antennas but are fundamentally different designs. But if you’re looking to simply extend your home’s WiFi range you might not need any of these, as Yagi antennas for home routers can be a lot simpler than you ever imagined.

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Lowering The Boom On Yagi Element Isolation

May 10, 2020 by 19 Comments

Antenna design can be confusing, to say the least. There’s so much black magic that goes into antennas that newbies often look at designs and are left wondering exactly how the thing could ever work. Slight changes in length or the angle between two elements result in a vastly different resonant frequency or a significant change in the antenna’s impedance. It can drive one to distraction.

Particularly concerning are the frequent appearances of what seem to be dead shorts between the two conductors of a feedline, which [andrew mcneil] explored with a pair of WiFi Yagi antennas. These highly directional antennas have a driven element and a number of parasitic elements, specifically a reflector behind the driven element and one or more directors in front of it. Constructive and destructive interference based on the spacing of the elements and capacitive or inductive coupling based on their length determine the characteristics of the antenna. [Andrew]’s test antennas have their twelve directors either isolated from the boom or shorted together to the shield of the feedline. In side-by-side tests with a known signal source, both antennas performed exactly the same, meaning that if you choose to build a Yagi, you’ve got a lot of flexibility in what materials you choose and how you attach elements to the boom.

If you want to dive a little deeper into how the Yagi works, and to learn why it’s more properly known as the Yagi-Uda antenna, check out our story on their history and operational theory. And hats off to [andrew] for reminding us that antenna design is often an exercise in practicality; after all, an umbrella and some tin cans or even a rusty nail will do under the right circumstances.

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On Point: The Yagi Antenna

May 24, 2017 by 86 Comments

If you happened to look up during a drive down a suburban street in the US anytime during the 60s or 70s, you’ll no doubt have noticed a forest of 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 20th century as cable providers became dominant, cast to the curb as unsightly relics of a sad and bygone era of limited choices and poor reception. 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 they’re designed specifically for HDTV. It’s 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.

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Simple Scanner Finds The Best WiFi Signal

April 21, 2017 by 8 Comments

Want to know which way to point your WiFi antenna to get the best signal? It’s a guessing game for most of us, but a quick build of a scanning WiFi antenna using mostly off-the-shelf components could point you in the right direction.

With saturation WiFi coverage in most places these days, optimizing your signal might seem like a pointless exercise. And indeed it seems [shawnhymel] built this more for fun than for practical reasons. Still, we can see applications where a scanning Yagi-Uda antenna would come in handy. The build started with a “WiFi divining rod” [shawnhymel] created from a simple homebrew Yagi-Uda and an ESP8266 to display the received signal strength indication (RSSI) from a specific access point. Tired of manually moving the popsicle stick and paperclip antenna, he built a two-axis scanner to swing the antenna through a complete hemisphere.

The RSSI for each point is recorded, and when the scan is complete, the antenna swings back to the strongest point. Given the antenna’s less-than-perfect directionality — [shawnhymel] traded narrow beam width for gain — we imagine the “strongest point” is somewhat subjective, but with a better antenna this could be a handy tool for site surveys, automated radio direction finding, or just mapping the RF environment of your neighborhood.

Yagi-Uda antennas and WiFi are no strangers to each other, whether it be a WiFi sniper rifle or another recycling bin Yagi.  Of course this scanner isn’t limited to WiFi. Maybe scanning a lightweight Yagi for the 2-meter band would be a great way to lock onto the local Ham repeater.

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Solving ISP Problem With A Homebrew LTE Yagi

May 13, 2016 by 33 Comments

We’ve heard reports that internet connectivity in Australia can be an iffy proposition, and [deandob] seems to back that up. At the limit of a decent DSL connection and on the fringe of LTE, [deandob] decided to optimize the wireless connection with this homebrew Yagi antenna.

Officially known as the Yagi-Uda after its two Japanese inventors from the 1920s, but generally shortened to the name of its less involved but quicker to patent inventor, the Yagi is an antenna that provides high gain in one direction. That a homebrew antenna was even necessary at all is due to [deandob]’s ISP using the 2300MHz band rather than the more popular 2400MHz – plenty of cheap 2.4GHz antennas out there, but not so much with 2.3GHz. With multiple parallel and precisely sized and spaced parasitic elements, a Yagi can be a complicated design, but luckily for [deandob] the ham radio community has a good selection of Yagi design tools available. His final design uses an aluminum rod for a boom, 2mm steel wire for reflectors and directors, and a length of coax as the driven element. The result? Better connectivity that pushes his ISP throttling limit, and no more need to mount the modem high enough in his house to use the internal antenna.

People on the fringes of internet coverage go to great lengths to get connections, like this off-grid network bridge. Or if you’d rather use a homebrew Yagi to listen to meteors, that’s possible too.

Building A Yagi-Uda Antenna

August 13, 2010 by 35 Comments

[Tommy Gober] built this Yagi-Uda antenna that has some handy design features. The boom is a piece of conduit with holes drilled in the appropriate places. The elements are aluminum arrow shafts; a good choice because they’re straight, relatively inexpensive, and they have #8-32 screw threads in one end. He used some threaded rod to connect both sides of the reflector and director elements. The driven elements are mounted offset so that a different machine screw for each can be connected to the appropriate conductor of the coaxial cable. The standing wave ratio comes in right where it should meaning he’ll have no trouble picking up those passing satellites as well as the International Space Station.