The body of knowledge held by Hams?
 

It is technical interest that differentiates the Radio Ham from the CBer.

In a world where so much is available off-the-shelf, where is the body
of technical knowledge to be found?

I suggest that it is still within fairly elementary electrical constructs -
capacitors,
inductors, and antennae. (OK, there are some auto-antennae tuners around now
for those who are determined in their CBness)