Geezerola is just a silly name I chose, you can call your radio anything you want This little radio is functionally identical to Armstrong's and my triode tube radios except, unlike triode vacuum tubes, the crystal in my triode will pass electrons without heating the cathode. Both this and Armstrong's radio need an 'A' battery and a 'B' battery. My regenerative radio from There is a link to my regenerative radio here and at the end of this story. The specified tube socket and the exact coil form were both unavailable, but half the fun of building this radio came from the opportunity to improvise like using a toilet roll for a coil form and to invent construction techniques that matched my building skills. Of course, I did not have the skill and tools to build the radio as it was described. I was very lucky because the 1H4 tube the project required was still available, otherwise the project might have ended right there.
I had built and experimented with crystal radios before, but I was ready to move up to something better. One project that really caught my fancy was the Armstrong Regenerative radio. Still, the book contained a lot of good, solid basic stuff and several wonderful projects that a kid could build and learn while doing. Morgan and his "Boy Electrician" book went back a long way, with the first edition printed in By the time I got this book, aroundthe technology in it was already 20 to 50 years old. The Heathkit CR-1 modified for two earphones.Back in the late 50s and early 60s my nascent career in electronics was encouraged by the many wonderful construction articles in Popular Electronics, Popular mechanics and Popular Science magazines, but it was a edition of an old book I found in the City Library that really got me going. Sensitive, high impedance headphones or earphones are a must.Ī modification so I can use two earphones. The importance of a good antenna and ground system. Most crystal radios use only one half of a radio frequency's wave. If you reverse the diode, the direct current undulations will be negative to zero to negative, but the same musical tone will be heard in the earphone. As shown here, the negative going parts of the wave are stopped by the detector diode so that positive to zero to positive undulations remain.
The dark black line is where the voltage is zero as a carrier wave crosses from positive to negative. More common is the waveform showing lower frequency sound waves superimposed on the carrier wave. Unmodulated carrier waves are also called "continuous waves" and can't be heard by a crystal detector except as a kind of a very faint hissing noise.ĪM radio stations try to avoid sending out unmodulated carrier waves called "dead air" and so this waveform is rarely seen. Graphs of the various waveforms seen at the tuner stage top two and at the detector stage. Here is a graphical representation of what's going on when a radio frequency signal is detected turned into sound. Imagine that we have a crystal radio like the one above connected to a long wire antenna. Imagine that our radio station is broadcasting hundreds of watts of energy into space and that if we could capture just a tiny amount of this energy, we would be able to hear what was being broadcasted. The way this radio works is as basic as it is possible to get and here's how it all works. Surprising performance from this kind of radio. My schematic diagram of the Heathkit model CR-1 crystal radio. A powdered iron ferrite slug is inside the tube between the two coils. The antenna coil is to the left of center. The antenna and the station tuning coils are wound on the phenolic tube. Back side showing the radio's components. My CR-1 crystal radio modified for two earphone jacks. A very selective and high performance crystal radio My Heathkit model CR Rebuilding my Heathkit CR1 and getting it to work.
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