We had to choose a few electives out of the scout handbook to do with our boys at home. One that stuck out was making a radio. There are a few different ways to build a radio, but the one they say dads used to make with their sons back in the 70’s were the crystal radios. The it hit me… my dad never built one with me. He and I built a lot of cool things together, but a radio wasn’t one of them. Then I thought, well, I haven’t built one with my son yet… so what the heck. The challenge was on.
I think the crystal radio is probably the most basic radio concept. It can capture AM radio waves within a 20-25 mile radius and using a resistor, a diode and a capacitor, you direct the radio wave in to something you can hear. Disclaimer: I’m a complete noob to radio, and that was half the attraction for me. That, and for some reason, I feel like I should expose my son at least once to capacitors, diodes and resistors. It turns we out we learned a lot about these components. Resistors have various colored stripes on them to identify the type and value of the resistor. There are ceramic and electrolytic capacitors, and all different types of diodes for your specific application. Resistors, limit the passage of electricity, diodes allow electric current to flow only one way, and capacitors store current, and condition it… providing a steady flow of current at a certain value. Pretty cool stuff right there! Apparently, the radio waves are that current… as this radio has no battery! It harnesses the radio waves, and by limiting and controlling the passage of current, we pound the signal something we can hear. I found a lot of resources on the internet and came across the bottle radio. This looked like a fun one to do. We even had to wrap the bottle with the magnet wire to make our tuning coil. Here’s the link to the bottle radio we made from lifehacker.com. They also tell you all the things you need, as well as how to build it. Going through the exercise is how you learn. Pay special attention to how they illustrate the germanium diode affecting the radio wave. It was really well done.
They said you can get almost all the things you need at Radio Shack, but alas, the location near me is nothing like the Radio Shack I remember growing up. There was one cabinet of drawers in the back that had the resistor I needed… but I had to order the germanium diode and the ceramic capacitor online. Still, cheap stuff and worth the fun with your kid.
We took the concept a step further and instead of hooking up the crystal earphone to hear the radio, we routed the signal into an electronics learning lab kit (that we did get at Radio Shack) and played it over a small speaker. This learning lab is pretty cool. You can build 200 different circuits from the book until you understand things enough to invent a few circuits on your own. For our radio, we built a 2-transistor amplifier on the bread board to amplify the radio signal. See a few pics below along with a video of the finished work below.
Be able to say you built a radio with your son, and have some quality time doing it. Here’s a video.