Making a Foxhole Radio (video)

Categories: Education, DIY


• Toilet paper tube

• Razor blade (If you can find a Blue one like the “PAL Super Single Edge” then great. Otherwise, you’ll have to blue it by heating it up)

• Earphone or old speaker

• Large safety pin

• Wood pencil stub

• Magnet wire

• A scrap of wood

• Paper clips

• Tacks

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The Coil

– I made this with magnet wire I had lying around. I’ve seen radios made with really thin wire, like I used, to thicker wire almost as thick as a staple. I used tape to hold it to the cardboard tube, but in retrospect, poking a hole and tying it on would be better. Wrap the wire around the tube 120 times and take time to make it smoosh together. I kept getting distracted from counting, so I ended up counting after winding. If it’s not exact, it shouldn’t be a problem. The amount of coils does matter for the radio station. If you get a station in sorta good, but it’s not perfect, you may be able to correct that by adding extra loops.

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The Detector

– Soldiers were given blued razor blades as part of their supplies. The bluing is some sort of oxidized coating from getting heated up, it probably keeps it sharper for longer. My research says that a rusted razor blade may work too. For me, I blued it with a propane torch and when I wiped it off after it had cooled, there was a layer of oxide on it and it was blue and purplish gray. I tried rusting a razor blade, but maybe it was stainless steel or something because it just wouldn’t rust. Salt water would be the best way to do it, but I just wasn’t patient enough!

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The Cat Whisker

– Take a pencil stub and poke the graphite with a safety pin. This works as a diode, but this is magic to me.

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– I used an old-school earphone from my bat detector project last year, but if you don’t have one, I would try out the earphones you already have before buying a new one.

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– I stripped a cat6 cable and used one wire to hang out the window. My wire is about 25 feet long, but longer is better!

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– I attached a wire onto the radiator. If you don’t have a radiator you could drive a coat hanger into the ground and wind a wire to that.

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Hook it all together

– I used brass tacks to keep it all together and paperclips to connect all the wires.

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Making it work

– The first time I tried this, it didn’t work. It was frustrating, but I just went through my materials, blued the razor blade and it worked. The second time I tried to get it to work, I couldn’t get a station, I just got buzz. I played with everything and finally figured out that the ground connection wasn’t very good. When I fixed that, I was able to hear sports talk radio! One of the interesting things is that it works better or worse depending on where you put the pencil lead on the razor blade. If it doesn’t work the first time, don’t give up!Screen Shot 2016-02-09 at 9.12.57 AM 

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