What's worth studying in the radio field, to combine hobby and get something useful?

Data communication seemed to me the most modern domain.

But now I can write to you that you are on another continent using a SIM card that gives at least $ 4 per three months and I have the internet included.

I have at my signature a link about 2G phone communication.
But that also seems "overwhelming"........

If we hardly study 3G communication 4G appeared and 5G is preparing.

conclusion:
I would like to spend time studying something useful.

A radio amateur activity from which I obtain technical information that will be useful to other people......

Edit: Sorry for writing mistake "Radioamator"="Amateur radio"

 

Data communication is a very broad topic.

Study depends on how deep you want to go, to designer level or just application level.

Hot areas today are wireless, which pulls from RF, Analog, Protocol areas of study.
Bluetooth the same.

Then there is wired technologies, like ethernet, serial, optical.....

Your question is a bit broad....


Regards, Dana.