Shortwave radio enthusiasts are sure to know the problem: You're trying to tune in to your favorite global broadcast only to find that the signal is fuzzy. Is it you? Your equipment? It might just be the conditions in the ionosphere, which you'd know if you built this DIY device.
As detailed in a YouTube video and project writeup on Hackster, North Macedonian maker Mirko Pavleski built himself a wee machine that measures ambient RF energy across the shortwave band, using it as a rough proxy for propagation conditions.
For those not in the know about shortwave radio frequencies between ~1 and 30 MHz, their ability to travel around the world is thanks to the ionosphere. When the layer of ionized gas that makes up the aptly-named ionosphere is thick and dense, it refracts more shortwave signals back to Earth, meaning shortwave signals bounce off the atmosphere more and arrive at receivers stronger and clearer.
A weaker ionosphere, meanwhile, means more signal escapes into space and that broadcast is harder to make out.
Knowing the level of ambient RF energy across the shortwave band can be useful information when you're a shortwave listener, in other words, and that's exactly what Pavleski's device displays.
The build is relatively simple, with basic components like an Arduino Nano R3, a small OLED, and, most crucially, a CA3089 chip used to translate raw RF signals into data the Arduino can display in an intelligible form.
The CA3089 is the trickiest part of the build, as you'll need to follow Pavleski's circuit diagram included on Hackster to wire up the passive components needed to make the whole thing work.
The data that the CA3089 outputs is also fairly raw, with its built-in received signal strength indicator providing a logarithmic voltage output corresponding to the strength of the received RF signals.
"I map the entire input from 0 to 1023, which means that the values on the display from 0 to 1024 correspond to a voltage from 0 to 5V," Pavleski explained, while noting that the Arduino code he included in the project can be altered to show a different value if desired.
However, you choose to have it display - you could even cut out the Arduino and attach an analog multimeter instead - Pavleski notes that it takes a bit of time to get a sense of what a particular reading means.
"After a few days of comparing the value of the instrument with the real received signal on the radio, we will know for sure when the propagation of the RF signals is bad, good or excellent, and that at the same moment when we look at the instrument," the Macedonian maker explained.
While shortwave radio operation is the obvious use of a tool like this, we can imagine other handy uses of it too: Maybe you want to record ionosphere activity for space-related purposes, are trying to correlate RF radiation to your local weather, or are a data hoarder looking for a new source. No matter the purpose, here's a project that'll suit your niche needs. ®
Source: The register