Later during the Vietnam War prisoners of war again built simple radios, and soldiers used Slinky springs as antennas. Hobby clubs still exist, that give information to persons who want to build a crystal radio or similar radio project. Swedish crystal radio from made by Radiola, with earphones. The device at top is the radio's cat's whisker detector. A second pair of earphone jacks is provided.
US Bureau of Standards Circular " A simple homemade radio receiving outfit " taught Americans how to build a crystal radio. Crystal radio kept at the Museum of the radio - Monteceneri Switzerland.
It uses a pencil lead attached to a safety pin pressing against a razor blade for a detector. The earth connection is usually an integral part of the antenna. Typically a long wire is suitable for this. For instance, a signal running at the upper bandwidth side of the intermediate wave spectrum requires a length of about ft for resonance, which is frequently too extensive for most household circumstances.
Because you need to attune the crystal radio to various frequencies, adjusting the length is a must. Thus, ft ones are not practical. As a result, the aerial adjusting circuit in the crystal kit is the answer. Its goal is to guarantee that the dipole can achieve the optimal resonance and the suitable impedance that fits the rest of the circuits.
There are also several methods for connecting the aerial to the set. Some designs link the antenna to the core tuner, but others use approaches to get the most efficiency out of the antenna. Moreover, several circuits also employ impedance equalization, either by an extra coil on the primary adjusting capacitor or through a button in the inductor. Occasionally, this combo is advantageous.
However, as the dual capacitors interplay with one another, adjusting the frequency becomes more complicated. Most of the time, crystal radios usually utilize a simple tuned circuit. The tuned circuit provides a passband within which signals are accepted. Well, "power" can mean a lot of different things. We often think of electricity as water, flowing out of our electrical sockets as needed.
In reality, it's a lot more complicated than that, and like water, electricity has waves, currents, and other characteristics that govern its various attributes. While you may think of radio waves and electricity as being different, they're actually the same phenomenon! Radio waves are just fluctuations in the electromagnetic fields that surround us at all times. Think of the waves in the ocean: they can push you around because each wave has its own kinetic force.
Well, you can kind of think of radio waves like invisible ocean waves. They're invisible to us, because they don't react with us. However, a copper wire can "see" the waves because it's a conductor of electricity! You can essentially think of the waves as vibrations.
When they hit a conductor, they make the conductor vibrate. In this case, the vibrations are so small that they're almost impossible to hear. That's why you need a crystal or diode to adjust the signal, and then a very, very sensitive earpiece to hear it. When you use a powered radio, it adds that power to the circuit, amplifying the vibrations until they become quite loud.
That's what the battery or plug does. No matter what kind of radio you have, it's always picking up the radio waves, even when the power is off. You just can't hear them unless you're amplifying the circuit because of the way modern radios are built.
Now that you have a general idea of the principle behind a crystal radio, let's look more specifically at the parts and how they work.
Not to be confused with the television show of the same name, the wire is the skeleton of your radio. Your wire is going to serve two purposes:. The radio wave catcher is known as your antenna, and the tuner is known as your coil. There are many configurations for both of these, but I'm going to cover it as simply as possible.
Well, that's a hard question to answer, because each type of wire has plusses and minuses. Generally you'll be dealing with two different types when it comes to crystal radios, insulated wire and magnet wire. For all intents and purposes on this project, insulated wire and magnet wire are the same thing.
It doesn't matter which you use, though you can see in the picture below that I used magnet wire. I picked magnet wire for a variety of reasons, but what was most important to me was that it looked more "steampunk". Plastic insulation is pretty modern-looking. You're going to need to pick a wire gauge, and that will affect your tuning ability. I went with a 16 gauge for mine, but I recommend slightly smaller, as that may be easier to work with.
So maybe go with an 18 or 20 gauge, but it's largely a matter of whether you prefer to work with a larger or smaller wire. We can adjust the tuning ability later, based on what gauge of wire you go with. When I first set out to make a Steampunk crystal radio set, I thought to myself, "Yes! I will find a real crystal for my radio, and it will be super authentic and awesome-looking! The crystals you can use for a crystal radio are pretty limited, and it's not like you can just hook it up to a piece of quartz.
Most of the crystals that are useful for a radio aren't ones that look particularly pretty, such as galena, which is a crystal form of lead. Second, tuning them is a gigantic pain in the rear. A crystal radio that uses a real crystal is called a "cat's whisker" set, because of the way that the wire dangles over the crystal. Essentially, you need to constantly hand-tune them while you're listening, or else you'll lose the signal.
It's terrible. So despite my earnest desire for authenticity, I had to compromise for the sake of not pulling my hair out and just use a modern diode.
While I could potentially have used a vacuum-tube diode, they're much harder to come by and still slightly past the Steampunk era. I may continue to look for one, though. As you can see from the picture, these diodes are type 1N34A, which suffice just fine for a crystal radio. You can actually see, if you zoom in really close in the above picture, that modern diodes are essentially just fixed-whiskers.
That is, it's a cat's whisker design, but it's fixed so it can't move. Well, that's a hard thing to explain. What a diode does is transfer a signal in one direction, but not the other, but that probably doesn't mean anything to you at this point. When you have a circuit, the signal will flow anywhere it can, even backwards.
If your signal is flowing both forwards and backwards, you're going to get a giant mishmash of signals if you try to listen to it. They'll cancel themselves out, and do all kinds of things, making it unlistenable. In order to fix that problem, you use a diode to filter your signal on the circuit. That way, you only receive one version of the signal at your earpiece.
If you want to think of it like our water analogy from earlier, think of a circuit as a pool. The water is everywhere in the pool at once, just like the electricity in a circuit. If you throw a stone in the pool, the ripples will flow outward, and if you had a way to measure the waves at the edge of the pool, you would get an unimpeded signal from the waves you made.
Now, imagine if you threw two stones in the water at the same time, at opposite ends of the pool. The ripples will meet in the middle and cancel themselves out, making the whole pool kind of wavy, but destroying the purity of either signal. The normal state of a circuit is like the two-stone model, but adding a diode turns it into a one-stone model, allowing a pure signal to be measured at the end. This is where your signal ends up, once you've collected it from the antenna and then filtered it with a diode.
In order to actually hear the signal, you need a special type of earphone; the ones you have sitting around your house just won't do. That's because modern headphones are designed to use power, far more power than you can pick up with a reasonably-sized antenna. Since you have very, very little power coming down your line, you're going to need an extremely sensitive earphone that will react to the tiny vibrations in your circuit.
This is called a "high impedance" earphone, or a "ceramic" earphone. Unfortunately, only one type of high impedance earphone is still being made in the entire world, and it's terribly ugly. There are a variety of places you can buy them from, but I did some research and discovered that they all come from the same factory in the UK.
Even more unfortunately, they're crap. The quality is just plain awful, because some just flatly won't work and other die in short order. And what's more, the manufacturer knows it, and refuses to do anything about it.
Nice, right? However, if you want to buy a new high impedance earphone, you're stuck because they're the only sellers. It comes with a normal 3. It's only one earpiece, but you need two wires in order to complete the circuit properly.
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