Here’s your video introduction to Section 6.2, “Signal Processing,” in the ARRL Extra Class License Manual for Ham Radio.
After you’ve finished viewing the video, studying the material in the text, and have become comfortable with the relevant test questions, you can return to the list of videos by clicking here.
By the way, if you’re interested in the book Crystal Clear: The Struggle for Reliable Communications Technology in World War II, the ISBN is 978-1-118-10464-4, and can be found on Amazon by clicking here. It’s written by a scientist rather than a writer, and that shows from time to time, but I found it fascinating nonetheless.