RTL-SDR.com

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…

Getting a license is your first step if you want to transmit. If you are in the US, the ARRL produces the training material for the various tests. There are free apps that go over the test questions but I like having a little more context to the answers.

With your background you'd probably need to devote time mostly to learning the rules and regulations. You can take all 3 tests in one sitting for a $15 fee and be done with it. Each test gets you more privileges (power, frequencies).

Even without a license you can receive with a cheap SDR and home brew antenna. This blog has many examples of that: https://www.rtl-sdr.com/

Finally, you may want to find a local club. Usually visiting during a "contest" will enable you to get on the air. In the US you don't need a license to use the radio if you are with a properly licensed operator.

Hope you find the hobby as fun as I have.

there's a lot of variety out there. you can spend your entire ticket dorking out on digital modes (esp if you go for general+ and have access to lower bands) like FT8, FT4, Olivia, WSPR [0] to see how far out you can get on as little power as possible and so on.

Or if you want to ease into it, you can get a ham radio w/o a license, or cheap SDR and try to receive and decode weather sats, etc [1]

making tiny WSPR boards and things like APRS [2] interest me more than ragchewing or nets on 40 or 80 meters most of the time

forgot my favorite, amateur SSTV (analog baby!) - can see some analog and hybrid (easylink over internet.. cheating) http://www.g0hwc.com/

0 - http://wsprd.vk7jj.com/ (click search then map to get an idea)

1 https://www.rtl-sdr.com/using-50-lines-of-python-code-to-decode-noaa-apt-weather-satellite-images/

2 https://aprs.fi/

If I were in your shoes (and I often am, in various other contexts), I'd get the cheapest SDR dongle, and then use your favorite search engine for tutorials (there's plenty).

First two hits for "how to get started with sdr" on duckduckgo give you awesome starting points:
- https://www.rtl-sdr.com/rtl-sdr-quick-start-guide/
- https://hackaday.com/2012/06/27/getting-started-with-software-defined-radio/

From there, figure out what device you're going to target. The 434 MHz devices are quite ubiquitous (and easy to understand) -- door bells, old school thermometers, remote switches, what have you.

Even without your own device, I'm sure you will find plenty of traffic near you (if you live in a reasonably densely populated area), so you can at least practice.

And then it's down to grinding it out -- read docs, experiment, repeat. :-)

HTH.

The 137 MHz band is sadly abandoned and the days of current satellites in the sky are counted. So if you are planning to experiment with satellite reception, HRPT is recommended at 1.7 GHz instead. Needs a more capable SDR device (however the RTL-SDR v3 might still fit if cooled properly), needs a more complex antenna, but the resolution is much better:

https://www.rtl-sdr.com/a-comprehensive-beginners-guide-to-hrpt-weather-satellite-reception/

Actually even the HRPT streams are seem to be phasing out, but will be supported on the MetOp line for a long time (MetOp-B has been launched in 2012, the -C in 2018, and the satellites generally have a 15 years of lifetime).
Future live streams will be transmitted in the 5 GHz+ range, which needs an even more complex antenna and probably a downconverter.

I got a LimeSDR when they first made them. Unfortunately the whole SDR software ecosystem is pretty terrible. Even with something as popular and widely supported as RTL-SDR most of the software is unusuable (with some happy exceptions). It also doesn't help that there is an absolute mountain of SDR software out there, but 99% of it is "this is cool, I'm going to write... eh nevermind" type stuff. There's so much ( https://www.rtl-sdr.com/big-list-rtl-sdr-supported-software/ ) that I can't even find the one good one I found last time I used an RTL-SDR.

I guess that is what happens if you play with software written by uber-nerds for uber-nerds.

Anyway in conclusion I would NOT recommend getting a LimeSDR unless you are really really into SDR and it's your only hobby, or better yet, your job.