IoTuesday: 3 Easy DIY Antennas That Increase Your WiFi and Bluetooth Range

Increase the range on your 2.4GHz IoT devices with these simple antenna hacks.

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Many inexpensive IoT development platforms rely on PCB and chip antennas to offer a WiFi or Bluetooth connection in the 2.4GHz Industrial, Scientific and Medical (ISM) band. Chip and PCB antennas offer a cheap, compact solution that fits onto a single board, which is often all that’s needed. They are also a good option if you really do not want a visible antenna on your final design.

ESP8266 Breakout

The ESP8266’s PCB antenna is clearly visible on the edge opposite the headers.

That being said, PCB and chip antennas can be a poor choice for a few reasons:

  • Proximity to other components on the board can affect performance.
  • If you build an enclosure around the board, the enclosure can also adversely affect the antenna’s performance.
  • While not exactly omnidirectional, many chip and PCB antennas are designed to allow for near-equal performance regardless of heading and orientation (with only a few nulls).

If you are attempting to shield your internet-connected environment sensor suite from the elements, you’ll likely want to consider mounting an external antenna onto your project to improve your connection. Some boards, like the ESP8266 Thing Dev, allow you to attach an external antenna to the onboard U.FL connector. Just note that you might have to move some solder around to make it happen.

Buying a good antenna can be expensive, and in the world of do-it-yourself (DIY) electronics, nothing beats making your own antenna out of household items. The three suggestions listed below are most certainly not omnidirectional. They are intended to help boost your range (gain) in a specific direction, which is why they’re known as directional antennas. You can learn a bit about omnidirectional vs. directional antennas here.

Disclaimer: I am not an RF engineer, and I know very little about antenna design and testing. The following homemade antennas were made by people with a lot more knowledge than me, but I can't guarantee they were tested in any official capacity. Make them at your own risk (which is, honestly, the fun part).

The Cantenna

Ian Buckley’s MakeUseOf article covers how to find a good can and turn it into a waveguide.

As it turns out, many store-bought aluminum cans are the perfect shape for a 2.4GHz waveguide (this tool will help you determine the perfect dimensions for your can). From Ian’s post, you’ll want a can that is as close to a 92mm diameter and 147mm length as possible. You then attach a copper wire to an N-type connector to make a probe that’s inserted into the side of the can. Depending on the type of cable and connectors used, you can potentially convert it to a U.FL connector to mate it to your development board.

If properly constructed, you can see a large increase in the range of your wireless connection; just be aware that Cantennas are highly directional, which means you’ll need to point the open end of the can toward your target (e.g., WiFi router). Some people report being able to maintain a connection over several miles with Line of Sight (LoS) in open air.

The Yagi-Uda

Homemeade Yagi antenna

Biotele creates a Yagi-Uda antenna out of paper clips and popsicle sticks on Instructables.

The Yagi-Uda antenna, commonly known as a “Yagi antenna,” was invented by Shintaro Uda and Hidetsugu Yagi in 1926. Prior to cable television, This type of antenna was commonly found affixed to roofs providing high-gain VHF and UHF television reception for many homes. The Yagi-Uda antenna typically consists of a driven element, a reflector, and one or more directors, where the reflector and directors are simply metal rods. The more directors on the antenna, the more directional the beam, which results in higher gain.

Making your own Yagi-Uda can be done very cheaply and requires only a few common tools. Instructables user Biotele shows you how to create your own 2.4GHz Yagi-Uda antenna with paper clips and popsicle sticks. MacGyver would be proud. Biotele claims to get an LoS range of 2 miles with this makeshift antenna.

Tripole with Circular Polarization

Tripole antenna

While more difficult to construct than the previous two, a circularly polarized antenna allows you to communicate with linearly polarized antennas oriented vertically or horizontally (just watch out for nulls). This is useful if you need to, say, talk to your Bluetooth devices in a garden outside your house.

Hackaday.io user HexHammer.Jez shows you how to build a tripole antenna to extend the range of Bluetooth (or anything in the 2.4GHz band). This antenna has a wider beam width than the Cantenna or Yagi-Uda, but HexHammer.Jez reports an LoS range of about 150 meters using an off-the-shelf USB Bluetooth dongle.

While you can certainly bump the transmit power to get more range (within the FCC limits, of course), using a directional antenna will offer a better connection between your IoT device and base station, assuming you have line of sight and your target is in the main lobe of your antenna (multipath interference can wreak havoc on wireless communications).

What are some other tricks you can think of to maintain a good wireless connection between devices without needing to bump up the transmit power?


Comments 3 comments

  • First, the vast majority of TV antennas are NOT Yagi-Uda antennas (despite what Wikipedia says). They are “log-periodic” antennas. A Yagi-Uda antenna has a relatively narrow bandwidth, but a log-periodic has a very wide bandwidth. The Yagi-Uda design has to be “tweaked” a little just to get enough bandwidth to receive one channel, while a log-periodic could easily get the whole VHF TV band (or, with some “tweaks”, the UHF TV band).

    Also, since the WiFi shares some frequencies with Amateur (Ham) Radio, if you have an Amateur Radio license, you can legally really kick the power up, though you have to be able to reprogram the “firmware” of your equipment to restrict it to ONLY use the Ham frequencies, you have to put your call sign onto the signals, and there are restrictions as to what data you can actually transfer (remember, it’s amateur radio – no commercial usage!). I have not tried this myself, but based on a presentation I’ve seen at a club meeting, you could go to this link for a starting point.

    • I was just looking at the Instrucables on building a Yagi, and Biotele suggested using nibblers to cut the paper clips, and that nibblers are available from Radio Shack. RS no longer carries nibblers (I found this out when I was building an Adafruit MintyBoost a couple of years ago), but DigiKey does have them in stock.

      • Thanks for the tips! Looks like my research on TV antennas was wrong.

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