As an example, I have some remote controlled ceiling fans in my house. They're controlled by dumb RF remotes, but I wanted to make them smart so they can be controlled from Alexa.

Being a total SDR novice I figured it'd be easy to use an SDR to tackle this. But after much searching, I discovered full-duplex SDR is _super_ expensive. I think HackRF is the cheapest one at ~$500?

So instead I grabbed an RTL-SDR dongle and some dumb, cheap RF transmitters (the fixed frequency kind that you just dump a digital signal into) that had roughly the same frequency as the fan's remotes.

It only took me a day to get the RTL-SDR working, capture some of the remote's signals, and decode them. But when I tried to recreate the signals using the RF transmitter I grabbed they only worked 10% of the time. Maybe my timing was off. Maybe my antenna was cruddy. Maybe the frequency of the RF transmitter was too far off from the remote's. I felt intimidated by the big, scary black magic of RF. So I gave up.

I ended up just cracking open one of the remotes and soldering relays to all the button pads. An ESP8266 later and I can control all the fans in the house using Alexa. Not bad for a day's work.

But it would have been a lot nicer and cleaner to just use a full duplex SDR. Awesome to see something affordable finally coming out!