Synopses & Reviews
Before WWI back before vacuum tubes were common, amateur wireless operators used crystal sets to listen to spark-gap transmitters sending morse code. Issues of Modern Electrics published by Hugo Gernsback in 1911 and 1912 routinely provided the Experimental Department where letters from experimenters were reprinted. Here you get the best of those letters.
Each small idea is illustrated, and I think you'll be amazed, as I was, by the wide variety of make-shift equipment that was being fabricated by impoverished experimenters. This isn't so much about crystal set circuits as it is about building the components needed, much like Pete Friedrich's book Voice of the Crystal provides.
You get ideas on building coherers, variable and adjustable condensers, loose couplers, sliders for tuning coils, making a universal detector, galena detectors, "tickers" for receiving Poulsen arcs (but where are you gonna find one of those these days?), and much more.
And, remember, this equipment was built in the home shop with simple equipment by people who, literally, didn't know what they were doing, but managed to get impressive results - back in the days when the Titanic sank. Back before the ARRL.
Great booklet of fascinating ideas. Rare material.