In this post, I’ll show you how to make a cheap portable spectrum analyzer from a TV receiver dongle. The dongle gets sold as a TV (DVB-T) however its an SDR(software defined radio) which means that it can be used to receive pretty much any RF signal(depending on the chip used up to 1-2 GHz) and turn it into a digital one to be later processed by software.
You can connect this dongle to your smartphone via a USB OTG(on the go) adapter and download one of the many spectrum analyzer apps that will process and display the data captured by the dongle.
And that’s it you have a portable DIY spectrum analyzer. It’s not as good as a proper spectrum analyzer that costs thousands but it’s dirt cheap and can do lots of other stuff as well. Like for example receive TV or radio(what is sold for), receive ADSB data from aircraft, and act as a “radar”, similar data can also be receieved from ships and weather balloons, you can recive satellite data(you need a proper antenna for that) and with something like GNU Radio you can do all sorts of other things with it.