There are lots of "this" in that article. There is SDR, satellite downlinks, Amateur Radio protocols, and receiving equipment.
My path started when I bought one of the RTL-SDR bundles from Nooelec (https://www.nooelec.com/store/). It came with four different antennae and some adapters to connect it to your own antenna.
I spent some time reconstructing projects that people had posted on rtl-sdr.com (https://www.rtl-sdr.com/). I installed Gnuradio companion (and various Gnuradio bits) and built an FM receiver as well as a receiver that could see the signals coming from a wireless light switch.
I decided I wanted to transmit too so I bought a HackRF-one (https://www.nooelec.com/store/hackrf.html). It covers way more spectrum than the RTL-SDR and it has great support in a lot of packages. What I wasn't able to do very successfully with it was look at cellular signals so when Crowd Supply ran a campaign for the Lime SDR (https://www.crowdsupply.com/lime-micro/limesdr) I got one of those. I recreated the cell basestation setup that the Myriad folks did using an old GSM phone I had in my drawer (marked "Cingular" :-))
I realized I wanted to be able to send more complex things at different frequencies so I took a detour and studied for, and received, my Amateur Radio "Extra" license (AI6ZR). Which allows me to transmit at much higher powers on many more bands.
There was a company near me that was making SDRs and they needed software help, I offered to help if they would let me use their very well equipped lab of RF gear. That gave me both access to and training on "real" RF gear and helped me understand what would be useful and what wasn't needed in my own explorations. Then I started haunting ebay, swap meets, and various auction sites to track down the gear I was missing. (A spectrum analyzer, a vector signal generator, and a vector network analyzer).
Bottom line, this rabbit hole just keeps going and going and going ...
Buy an RTL-SDR on amazon (20-30$). Start playing around with the software. Listen in on aircraft and such. Then start reading about catching satellites.
These things are super fun. I use one to track airplanes and weather in flight with the stratux project. (http://stratux.me) It pairs the USB radio receiver with a raspberry pi and broadcast the location of ADS-B equipped aircraft to your tablet with flight tracking maps. No internet for most of us in a bug smasher - the data comes in over radio waves.
A lot of this builds on Amateur Radio experience. If you dont have a licence, start there. You dont need a license to receive radio transmissions, but the learning involved in getting a license will give you a start on taking on more difficult projects.
