1. Using frequencies for healing requires a delicate dance of understanding between the frequencies themselves and the biology of the body. Basic concepts will be fairly easy to absorb (especially for you with the electrical background) but the understanding (or intuition) of biology is what makes magic happen in healing. To get a better understanding of that in one read, I would recommend a book by Hulda Clark. This is a good beginning to understand a lot of the conversation here.
2. My understanding is that Royal Rife developed the world's most powerful optical microscope that allowed him to see bugs alive, and watch them die as he applied frequencies. I don't believe that the general public has access to such equipment anymore, as most modern equipment that can see viruses kills the specimen (ie: electron microscope). There have been other advances, such as the "Nanoscope", https://www.cnet.com/news/nanoscope-makes-live-viruses-visible-for-first-time/, but again, out of reach of the public. I suspect such equipment is kept from the public because they don't want us to know how common pleomorphism really is.
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