Quartz crystal is used in radio tuning.
Building your own crystal filter for your radio is both entertaining and educational. Quartz crystal is used to create ladder filter, which serves as a radio receiver to receive sideband signals. Although filters are fairly complex, a simple filter can usually be constructed from the use of crystals with similar frequencies.
Instructions
1. Measure the capacitance of your crystals. "Capacitance" is a term in electromagnetism used to describe the ability of your crystals to store energy. The National Association for Amateur Radio recommends learning as much as possible about the properties of the material you construct your crystal receiver with. Crystals with a high capacitance are needed for radio construction. Measure the capacitance by using a component test set or a bridge. To ensure you get an accurate measurement, place the crystal in a position similar to how it will rest in your final construction.
2. Test the motional inductance, or Lm, and the motional capacitance, or Cm, for each crystal -- using a 3-decibel attenuator and a stable-signal generator. Write these down, along with the capacitance. These values will be needed later as you configure the filter. Motional inductance is the ability of the crystal to store and move energy through the electromagnetic field and is directly related to the mass of the quartz. It is a measurement of frequency in Hertz. Motional capacitance is measured in farads and is the load capacity of the crystal in terms of how much energy it can handle. Make note of the crystals with the highest and lowest frequencies -- because these will be used for the purpose of serving as carrier crystals. The most cost-effective and simple filters typically utilize filters with frequencies ranging from 5 MHz up to 40 MHZ.
3. Use a filter-design program to simulate the resulting filter you'll build with the crystals you have available. Adjust your filter by using L-networks or transformers to match the desired impedance. Impedance is the measurement or ratio of electrical and magnetic fields in a magnetic wave.
4. Prepare your crystal-filter components by attaching the crystal cases to a metal ground wire clip, known as a Fahnestock clip, and winding the inductors on cores with #28 enamel wire. Solder all the connections to ground on a copper-clad circuit board. Add tuning dials to your radio circuit to hone in on one radio frequency.
5. Test your filter. It should work according to the specifications you determined, using your design program. Crystal filters do not require a separate power source. Instead, they simply attract already existing radio waves and transmit them through the crystal, in the form of energy, to the ground wire. Your tuner works just like any other radio turner. Turn one or more dials to prevent the radio from reading more than one station at a time. You'll tune into one station at a time, just as you would using a radio dial in a car that requires you to turn the tuner.
Tags: crystal used, crystals with, ground wire, Measure capacitance, Quartz crystal, Quartz crystal used,