a Radio or a Watch?

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a Radio or a Watch?
-the magic of Quartz Crystals

Quartz crystals are made of silicon dioxide like most sand. The mineral is found in a huge variety of rocks in the crust of the earth.
What makes quartz interesting is that the crystals have three very interesting properties..
  1. Quartz is durable unaffected by most solvents and remains crystalline to hundreds of degrees celsius.
  2. The property that makes it an electronic miracle is the fact that, when compressed or bent, it generates a charge or voltage on its surface. This is a fairly common phenomenon called the Piezoelectric effect. In the same way, if a voltage is applied, quartz will bend or change its shape very slightly. If a bell were shaped by grinding a single crystal of quartz, it would ring for minutes after being tapped.
  3. When any quartz crystal vibrates it always does so at exactly 32768 times each second.

So quartz crystals can be used to make Radios and to make very accurate Watches

Radio stations send their content out by generating electromagnetic waves.

A small amount of energy from the radio wave is captured by the antenna wire and is taken to the coil. The coil has to be designed just right to capture only the frequency we are trying to receive. So for example the Am frequency  610 kHz.

The height peaks and troughs from an AM radio station  sends the sounds through the air

By winding just the right amount of wire on just the right diameter coil form, the coil will be what we call "resonant" and "ring". In other words it will be able to store the energy of the radio wave we want to hear. All other radio waves not "resonant" will pass through the coil and out the other side to the ground.
A small amount of the radio wave energy stored in the coil (our 610 kHz or 610,000 cycles per second) moves to the detector or the device called a diode, in this case a quartz crystal is used. The energy is an alternating current signal (AC) at this point. The quartz crystal detector (diode) rejects half of the alternating current signal and the signal looks like image below. Now the signal is a pulsating direct current (DC) signal that can be heard as sound in the earphones.

If both sides of the wave were used, they would cancel each other out as they are opposite of each other. As this energy goes into the earphone, the amplitude or strength of the signal varies because the wave is "modulated". This energy is converted by mechanical means in the internal workings of the earphone. The sound waves exit the earphone which you perceive as the original sounds from the radio station.

You can tune the coil to get different frequencies. That can be done by adding more turns of wire around the coil form. Or removing some. On a simple radio, this is done by sliding the wire from the quartz crystal along the length of the coil making the coil longer or shorter. , until the desired radio station is found..

The lead mineral crystal galena can also be used as a detector / diode. Diodes, in this case crystals only permit  a signal to move in one direction so the peaks and troughs of the radio wave are converted to just peaks.

Watches Quartz watches work because the crystal itself is piezoelectric, which means it vibrates when you apply an electrical current to it.

All quartz crystals, if shaped in the right direction to the crystalline axis, vibrate at a very at exactly 32,768 times per second.
The best quartz crystal shapes are a straight bar or a disk. A bar has the advantage of keeping the same frequency provided the ratio of length to width remains the same. If the surface voltage on the crystal is picked off with plated electrodes and amplified by a transistor or integrated circuit, it can be re-applied to keep the crystal vibrating.

Do quartz crystals have magical healing properties?
They have interesting properties but no medical studies directly indicate healing powers.