My first experience with radio came when my grandfather, in the third grade, built a crystal radio for me. This sparked some interest, and later I was able to build one myself (though it took a lot of trial and error). However, I'm more drawn to the "Unified Communications" approach (although the actual number of QSOs isn't that high).💦), and the experience and knowledge were also quite mixed, making it difficult to connect different concepts. Its scope is very broad, covering physics, mathematics, computer technology, and more. I want to systematically learn the basic theory and practical experience of radio technology. I'm asking members of the forum, specifically experienced HAMs, if they can recommend some easy-to-understand books or courses. Specifically, I'm interested in learning about antenna principles and signal circuits (I've also watched some videos on Bilibili, but my current high school knowledge is limited, and I haven't yet mastered some more advanced concepts). It feels like without a solid foundation of practical knowledge, it would be very difficult to progress in radio technology.💦 Could you please provide some advice for fellow HAM radio enthusiasts? QWQ🤗