My goto sites for documentation are

Blogs that I frequent

I used ACloud Guru and Udemy to study for AWS Certification exams. Both the sites had good material to help prepare for the exam. In the end I think having hands on experience does make a huge difference. 

Amateur Radio

I am a Technician Class Amateur Radio Operator. I get my Radio news and events related to ARRL.

For those who do not know, ARRL is a non-commercial organization of radio amateurs. You can read more about ARRL.

Here is a link to the Band Plan page, which tells you about the voluntary division of a band to avoid interference between incompatible modes.

Frequency Charts