Crystal

crystals are widely used from the start the radio, Handy Talky, tv, phone, etc.. at a high frequency generator (oscillator) for frequency oscillator can be maintained stable, in addition to a stable frequency, a crystal oscillator has a very narrow bandwidth. Crystals used in aircraft radio is mostly a piece of quartz crystal pieces. Resonant frequency depends on the thickness of the pieces, for example for a 7 MHz thickness of about 0.9 MM.
Oscillator RF (radio frequency power) is the main part of a transmitter. These sections specify the frequency of a transmitter, and therefore required an oscillator that is stable. In order to guarantee the stability of an oscillator used crystal that serves as a driver driving the oscillator. Limits on the frequency change should not be shifted more than 0.002% of the crystal frequency.
Crystal also has a very good temperature stability. Typically, the temperature coefficient of ± 50ppm crystal was dikisaran direntangan normal operating temperature of -20 ° C to +70 ° C. Comparing with the temperature coefficient of capacitors which can reach several percent. For applications that require a higher temperature stability, the crystal can be operated in a small oven temperature is always kept constant.

As we all know that a quartz crystal to provide the piezoelectric effect. Other piezoelectric material which is or the name of Rochelle Salt Potassium Sodium tartrate chemical properties, such crystals are mostly used for microphone or headphones to speakers.
To create a crystal with a high frequency (above 20 MHz) is rather difficult to make accurate thickness. Usually used for high frequency crystal with a frequency below, then the oscillator is given so that the output harmonic filter. Crystals that work according to the thickness of the pieces on crystal frequency called the fundamental crystal and crystal work 3 or 5 time called overtones.
Besides its use as an oscillator, microphone and speakers, the crystal is also used as a filter. Crystal filter consists of a series of ladder crystal filter or a series of lattice filters, crystal filters specifically designed to have three legs.