Something I've had a longstanding desire to learn about is radio frequencies. I'm a very visual person, but I have yet to find any resource that explains it in a way that really makes sense to me. Especially when you start getting into modulation and whatnot. I'm fortunate to be able to use a variety of wireless technologies at work (licensed 80GHz, 18GHz and 950MHz frequencies), but I admittedly only have basic working knowledge and don't clearly comprehend what's happening at the lower physical level.<p>Does anyone have a good recommendation on any material that really made wireless technology understandable for you?