© Emil L. Decker

Resonance is defined as the induction on a physical object of vibrations by a vibrating force having the same frequency.

© Emil L. Decker

Probably the most famous incident in which this resonance resulted in destruction is the case of the Tacoma Narrows Bridge.

University of Washington Libraries, Special Collections, UW21422.

© Emil L. Decker

Every bridge constructed will vibrate at some natural, or resonant frequency, however the engineers who designed this bridge did not check the rate of the bridge’s resonant frequency.

University of Washington Libraries, Special Collections, UW21412.

© Emil L. Decker

Unfortunately, the bridge’s natural resonant frequency was the same as the wind blowing across the Puget Sound on certain days.

University of Washington Libraries, Special Collections, UW20731.

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During times when the conditions were just right, the energy from the wind was transferred to the bridge.

University of Washington Libraries, Special Collections, UW21429.

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As the amplitude of the wind induced vibrations became larger and larger, the bridge ultimately gave way and collapsed.

University of Washington Libraries, Special Collections, PI-20798.

© Emil L. Decker

University of Washington Libraries, Special Collections, PH Coll. 290.49.

University of Washington Libraries, Special Collections, UW21431.

© Emil L. Decker

University of Washington Libraries, Special Collections, PI-20797.

University of Washington Libraries, Special Collections, UW26818Z.

© Emil L. Decker

University of Washington Libraries, Special Collections, UW23030.

University of Washington Libraries, Special Collections, UW21414.

© Emil L. Decker

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© Emil L. Decker

Crystals resonate at a given frequency, when energy is induced into their circuitry. By modulating a signal onto that frequency, transmitters and receivers can, if their resonant frequency matches, transfer that signal.

Animation courtesy of Dr. Dan Russell, Kettering University

© Emil L. Decker

Let’s look at a typical crystal designed to transmit such a signal. The crystal is usually marked with the frequency at which it will oscillate, as well as whether it is the Tx or the Rx crystal. These cannot be interchanged.

Tx 27 Mhz

Rx27 Mhz

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When placed into a circuit, the crystal will vibrate at its resonant frequency

Radio Wave animation courtesy of Dr. Dan Russell, Kettering University

© Emil L. Decker

Electrons will flow within the alternating current, and be passed on to an amplifier, which strengthens the signal.

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Radio wave animation courtesy of Dr. Dan Russell, Kettering University

© Emil L. Decker

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The amplified signal is sent up an antenna and propagated out in radio waves.

Radio wave animation courtesy of Dr. Dan Russell, Kettering University

© Emil L. Decker

The movement of the electron is essentially generating the first half of a sinusoidal wave.

Animation courtesy of Dr. Dan Russell, Kettering University

© Emil L. Decker

The electron flow then reverses and completes the second half of the sinusoidal wave.

Animation courtesy of Dr. Dan Russell, Kettering University

© Emil L. Decker

eeeeeeThis completes one single cycle as the electron returns to the crystal.

Radio wave animation courtesy of Dr. Dan Russell, Kettering University

© Emil L. Decker

A full sinusoidal wave in action.Animation courtesy of Dr. Dan Russell, Kettering University

© Emil L. Decker

This is only half of the signal’s trip. As the signal hits the Rx antenna, electrons are induced to flow down the antenna and to an amplifier on the receiver.

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© Emil L. Decker

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As the electrons travel to the receiver, the Rx crystal will begin to oscillate if the frequency matches its resonant frequency.

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Radio wave animation courtesy of Dr. Dan Russell, Kettering University

© Emil L. Decker

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Should the crystals in the transmitter and the receiver not match, the receiving crystal will not vibrate, and the signal ends there.

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© Emil L. Decker

The electrons then travel towards the micro controller. This represents the first half of the sinusoidal wave at the receiving station.

Animation courtesy of Dr. Dan Russell, Kettering University

© Emil L. Decker

The electrons then reverse themselves and travel back the way they came completing the second half of the sinusoidal wave.

Animation courtesy of Dr. Dan Russell, Kettering University

© Emil L. Decker

They travel back through the crystal, amplifier, and back into the antenna.

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Radio wave animation courtesy of Dr. Dan Russell, Kettering University

© Emil L. Decker

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They travel back through the crystal, amplifier, and back into the antenna.

© Emil L. Decker

There is a relationship between time, the frequency and the cycles. Frequency equals one divided by time. Time is measured by what it takes to complete one sinusoidal cycle.

f = 1T

© Emil L. Decker