RF still seems like a black art in many ways to me. When you look at the surface of this antenna, the mind simply boggles — how can this work as an effective antenna, especially across such a wide frequency range? Well, this 300MHz-3GHz Log Spiral Antenna might just be the perfect antenna for applications like LoRa, Bluetooth, and other ISM band applications.
For those of you not familiar with LoRa, it is a low-power wide-area network specification. It uses the ISM sub-gigahertz bands, meaning users don’t need a license to operate it. It can be very efficient over surprisingly long distances. It has proved extremely popular in IoT projects, especially those located outdoors, as the low power requirement fits perfectly with embedded devices. They form a network which reports back to a base station — a role this antenna would be perfect for.
The antenna was tested by a company called AntennaTestLab. The above image is the antenna being tested in their anechoic chamber! The results were very interesting. This animated GIF shows a Smith chart of the results by frequency — and I’m not ashamed to admit I spent far too long staring at it! I’m far from an RF expert, but I found it very interesting to note that the two polarizations are not always mirror images of each other. If you’re interested, Hex and Flex (the designer) has a lot more information about the test results on their website.
Of course, it also covers the 2.4GHz ISM band, which means it could be used as a bidirectional WiFi or Bluetooth antenna. While it doesn’t have a lot of gain at 2.4GHz, the directionality could be used to help cover a part of your home or property that isn’t reached well by your router. This antenna is also great for Global Navigation Satellite System (GNSS) applications, such as GPS, GLONASS, Galileo, and BeiDou.
And finally, it just looks super cool! If you want to give a wireless project a bit of extra flair, having a cool looking antenna can be just the touch you need. Family and friends will be sure to ask “What the heck is that thing?!” every time they visit.
