Found this link, might be of help to you.

On 26 Aug 2003 21:32:12 -0700, (Christopher) wrote:

how exactly do shortwave radio's work? Can someone please direct me to
a website which explains the essential aspects behind this technology?

I feel bad because I work in an electronics store, and we do carry
shortwave radio's....although customers haven't really asked in-depth
questions about it as yet. I just want to prepare myself. Thanks.