On Tue, 28 Jun 2016 23:41:21 -0400, rickman wrote:

The term "amateur" is often applied to people who have obtained a
license to use radio equipment for communications. Is this term
inclusive of those who don't obtain a license but use receivers for
various uses?

I believe the term was used to describe anyone that indulges in RF but
does NOT charge for their efforts. The FCC wanted to distinguish
between commerical (for profit) services, and amateur (not for profit)
services.

For reception only, the term was "SWL" or short wave listener. I
guess that also applies to only listening on just about any frequency
from ELF to satellite communications.
https://en.wikipedia.org/wiki/Shortwave_listening
No license required to just listen.

I have been looking into design of receivers in the LF to ELF frequency
ranges. Is this part of "amateur" radio?

Mostly yet. However, some bands do not require a license and operate
under FCC Part 15:
http://www.lwca.org
https://en.wikipedia.org/wiki/LowFER
http://www.arrl.org/lf-low-frequency
https://hackaday.io/project/6882-lowfer-transmitter-for-your-arduino
etc...



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558