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Devin and Ian Build a Crystal Set

2017-09-08 03:28  
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Simple crystal radio.

This is how it all began.

This is how it ended.

Crystal radio unbuiltThe finished project

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Hi again friends. This will be a little different than my usual crystal sets projects. This time there is a cast of 3! Devin and Ian came over to build a set with me. This project turned out well.

This radio is built like my #36 radio. That is, a single coil and dual gang variable capacitor. It is a good design with better performance than the standard single gang capacitor circuit that is popular.

I first explained how radio works. Here is what I said. Lets say that the two boys want to talk with each other. They might get a half a block away and then they can't hear each other. They need some way tocarrytheir voice further. Audio frequencies don't carry well in air. However radio frequency energy does travel a long distance. How about letting the transmitter carry the voice. So the voice is added to the carrier. Since we can't hear radio frequencies, we need a way to convert them back to the audio. The radio receiver is adjusted so the resonance of the coil and capacitor together equal the frequency of the radio frequency to be received. Think of blowing across a soda bottle. You hear a tone. As the soda is consumed, the tone gets lower. The radio, through the detection process removes the radio frequency energy and leaves the audio. This is passed on to the earphone.

The first task is to wind the coil. Devin did the winding while Ian kept count of the number of turns. He had a little difficulty as the slits were quite narrow. It was mentioned that winding spider coils might be a good way to relieve stress. After winding hundreds, I should be real mellow now. :)

After the coil was wound it was time to take a trip to the shop (my kitchen). The solder lugs were bent, the terminal screws and nuts were tightened. Then the coil and capacitor were mounted.

The next step was to solder the wires and components. Following the hand drawn diagram, we all took turns wiring the radio. Those boys learned to solder real fast. Before testing, we went through the wiring, step by step. I felt like Mr. Wizard!

Now for the test. Devin took the first listen. He heard one of the local stations coming in well. We did find that the radio didn't quite hear the highest frequencies, so a few turns were removed from the coil. Additional testing was done.

Ian and Devin were excellent students. It was a pleasure to build a radio with them. I hope that you will find the time to make a radio with a younger person.

73 and good crystal DX. Dave - N2DS

Dave's Homemade Radio Build
Dave's Homemade Radio Build
Dave's Homemade Radio Build

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