When I was 13 y.o. a neighbor gave me a copy of that book. I devoured it. I built a one tube (6J6 I believe) 10 watt 40m cw transmitter from its pages. It started a fire in my belly to learn electronics and mathematics not to mention the indescribable thrill of transmitting "cq cq cq de wb6pnm" and getting a response from a station over 1000 miles away with equipment I had built with my own hands. I wanted to know how my antenna radiated radio waves and I wanted to know how the ionosphere worked. I had thousands of questions. My father (a physicist) said; "You will only get the answers if you go to university and learn experimental physics". So I did. Sadly, young people today do not have this experience.I consider first hand information like this to be like peer review information. I'm going to change it to the 5U4. Thank you. :)
Here's a future beauty I'll be working on but it's what's on top that's very special to me.
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It was a gift from a good friend and I used it to look up the base diagrams for the tubes in order to verify they were indeed interchangeable. ;)
Thank you so much for posting these photographs. I was flooded with happy memories.