12/25/2023 0 Comments Miniature transistor radioAlthough no batteries nor power source is needed, I installed an on/off switch, so as not to bother anyone nearby when I wasn't using it. IF you are thinking of just using a slider, no taps are t up the slider to rub along the coil and use it to wear into the coating so you have contact all along the coil. I went all fancy and instead of using a simple slider type assembly as found in many crystal radio kits, with this one I attached 6 on/off switches to a panel and one rotary switch (10 position). Once fully wrapped, I taped the end down so they'd not move, and sanded the tap loops, so as to have bare wire. Do NOT break nor cut the wire at any time during this process. I made 16 taps (that is, after every 5-7 turns around the coil form, I'd pull out a small loop and glue or tape it in place for later, and continue to wind the coil. The coil was made with 22 awg coated wire wrapped around an old Quaker Oats style tube / container, cut down to size. Now, to vary the capacity, one need only slide one of the sheets part way out of the book to decrease capacitance, or push it back on for more. Not shown was the variable capacitor I made by placing a full sheet of aluminum foil between the pages of a book, and another sheet a page below that one. Be careful though, cupric chloride is poisonous, as are the innards of any battery. The penny is a good example, if the outer copper coating has some greenish cupric chloride layer over it, the copper is rendered less conductive.īlue limestone, tarnished silver, carbon rods from old batteries, etc all make for useful testing. One could find it EVERYWHERE when I was much younger.now I have difficulties finding ONE PIECE.Įxperiment though, somethings are semi-conductive and will work better then fully conductive bits. I would picture mine, but I haven't a clue as where where the "cleaning lady" put it *sigh*.Īnother GOOD "crystal" is a bit of pyrite (I'd used this also as a youth, but haven't seen it lying around of late. In fact, that is what they normally supply one with, when one buys a kit. One of the BEST "crystals" to use as a detector, is a Galena block that is broken. Gluing a double edged razor blade, one that has blue streaks running through it, is fine, so the blades are no longer exposed, and you have a nice flat surface to move your "whisker" over. Another old time semiconductor was an old rusted razor blade.ĬAUTION: RAZOR BLADES ARE VERY SHARP, AND WHEN RUSTY CAN HARBOR TETANUS VIRUSES. I have tried old corroded pennies (newer ones contain so little copper that they are almost useless here, but your rig may work with doesn't hurt to try. The other half of this crude diode, will be some semi-conductive material. Make sure the graphite point sticks out beyond the metal pin.we are using the graphite/metal combo as a "detector pointer" or "cat's whisker" as they once were called. Now you can solder the copper wires, and this will hold the whole thing together pretty well. Taking a safety pin and clipping off the "point" so as not to shove the thing through your finger while you work, and also taking a bit of pencil "lead" (graphite and clay is what it really is), Hold it against one leg and wrap some stripped thin copper wire around it, lashing it to the metal leg. It IS however, adjustable.īy adjustable, I mean the detector point can be moved about to find the most sensitive (responsive) area. This is NOT a typical diode however, and will work best with low power radio signals. We installed a transistor radio so we could turn it on and just have it work.This is where I promised to demonstrate the construction of a home made diode out of household items. It worked but was mostly for show because it took a bit for the tubes to warm up before you could listen to anything. I had a 1955 Chevrolet Bel-Air in high school and the thing had it's original, tube radio. Transistor radios could be portable, you didn't have expensive tubes to replace and the things didn't have to "warm up" to be useful. Let's not forget that one of the reasons the transistor radio replaced ones powered by tubes was sheer convenience. Computers were much more affordable, too, thanks to transistors and that low cost made it possible for consumers to afford the things after home computers hit the market. Transistors replaced valves, paving the way for smaller, more reliable computers. Computers used to use vacuum tubes, too, and were huge and somewhat unreliable in those days.
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