Powerful Workstations 2010

Power Sources Electromagnetic Spectrum Oscillators

SUBJECT: RADIO AM FM UNIT I

SO DOES THE ELECTROMAGNETIC SPECTRUM



RADIATION OF ELECTROMAGNETIC WAVES

oscillation or acceleration of any electrical charge generated a physical phenomenon consisting of electric and magnetic components, spectrum of radiation known as electromagnetic waves.

Fig. 1 full spectrum of radiation of electromagnetic waves.


That spectrum can be ordered from waves that have very low frequencies of a few hertz (Hz) or cycles per second with very long lengths, such as the frequency of the alternating current we use in our houses, until a very high frequency waves, thousands of millions of hertz or cycles per second with extremely short lengths, such as those with cosmic radiation.

The only difference between a wave group and others within the electromagnetic spectrum is the frequency in hertz (Hz), its length in meters (m) and transmit energy level in joules (J).

Main features of electromagnetic waves

The three main characteristics of the waves that constitute the electromagnetic spectrum are:

Frequency (f)

Length (λ)

Amplitude (A)


Frequency

The frequency of a wave corresponds to a physical phenomenon that is repeated cyclically a certain number of times for a second time, as shown in the following illustration:
fig. 2
A. - sine wave cycle or hertz (Hz) per second. B. - Sine wave of 10 cycles or hertz per second

The frequency of these waves of the electromagnetic spectrum are represented by the letter (f) and its unit of measurement is the cycle, or hertz (Hz) second.


wavelength

spectrum electromagnetic waves propagate through space in a similar way as water does when you throw a stone into a pond, that is, generating waves at the point where it falls the stone and extending to the shore.

When we throw a stone into a pond, waves are generated similar to
radiation characteristic of the electromagnetic spectrum.


Both waves are produced by displacement of water as the waves of the electromagnetic spectrum have peaks or ridges and valleys or bellies.

The horizontal distance between two consecutive peaks, two consecutive valleys, or even twice the distance between a node and other electromagnetic wave, measured in multiples or fractions of meters (m), constitutes what is called length wave. "

P. - Peak or crest: the maximum value of positive sign (+), takes the sine wave spectrum. electromagnetic, each half cycle, from the "0". This value increases or decreases as. amplitude "A" of the wave increases or decreases very positively over the value "0."

V. - Valle or womb maximum negative value (-), which takes the sine wave spectrum. electromagnetic, each half cycle, as it descends and crosses the "0". . The value of the valleys. increases or decreases as the amplitude "A" of the wave itself grows or decreases negatively. below the value "0."

T. - Period: time in seconds that elapses between the passage of two peaks or two valleys for the same. point.

N. - Node: Value "0" of the sine wave.

a wave length of the electromagnetic spectrum is represented by the Greek letter lambda. (Λ) and its value can be found using the following mathematical formula:

Where:

λ = wavelength in meters.
c = speed of light in vacuum (300 000 km / sec.)
f = wave frequency in hertz (Hz).

For example, if we want to know what band in meters (SW) transmits a radio station that is captured in the 7.1 MHz frequency on the dial, proceed as follows:



The speed of light (300 000 km / sec) become m / sec, to get the final result in meters. This operation is performed as follows, taking into account that 1 km is equal to 1 000 meters:

300 000 km / sec x 1 000 m = 300 000 000 meters / sec



below the 7.1 megahertz are converted in hertz (Hz), which is the unit of measurement frequency, given that 1 MHz is equal to 106 Hz, or 1 million Hz: 7.1 MHz x

106 = 7.1 x 1 000 000 = 7 100 000 Hz (or 7.1 million cycles per second)



The result of these two conversions substitute their values \u200b\u200bin the above formula and we have: Therefore
, the wavelength of the signal of 7.1 MHz will be 42.2 meters per cycle or hertz frequency. This length corresponds to the range of short wave radio (OC) that respond to the band corresponding range of 41 meters in the face of a receiver.


Wavelength

The amplitude is the maximum value that can reach the crest or peak of a wave. The point of less value received the name of the valley or belly, while the point where the value vanishes in passing, is known as "node" or "zero."

properties of electromagnetic waves

for its propagation of electromagnetic waves do not require a specific material medium, it can travel even outer space.

electromagnetic waves, as mentioned above, are spread by the vacuum at the speed of light (300 000 km / sec approximately), until your energy runs out. As the frequency increases, the wave energy increases.

This type of wave has the same physical properties
wave motion inherent



Research: Mr. Ricardo Arreola Navarro

January 2008 CETIS 58

Subject: Radio AM FM