Freq Spectrum

7/25/2019 Freq Spectrum

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Electromagnetic

spectrum

1 5

The Ele

Electromagnetic waves a

magnetic fields vary at a

the polarity reverses a g

vary Their f

These oscillations may o

The range of electromagn

electromagnetic spectrum

All electrical and ele

magnetic 'pectrum. ot

ma)


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f igure 1-14 The electromagnetic spectrum used in el

Name Frequ

Extremely low frequencies

(ELFs) 3Q-3

Vo ice frequ

en

cies (VFs) 30Q-30

Very low frequencies (VLFs) 3-30

Low frequencies (LFs) 3Q-3

Medium frequencies (MFs) 300 kHz-3

High frequencies (HFs) 3-3

Very high frequencies (VHFs) 3Q-30

Ultra high frequencies (UHFs) 300 MHz-3


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l yd). Wavelength is m

wave, as Fig. l- l5(h) sh

is the distance that one

cent peaks

or

valleys o

Wavelength is also t

one

cycle. Electromagnet

of light and radio waves

(3

X J

0

8

m/

s).

or

186,0

less.

The wavelength

of

computed by dividing

A = 300,000.000/f For


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Example

1 2

A signal

with

a wavelength of

1.5

m has a frequenc

300

r-

=

2oo

M. 1.5


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Voice

frequency

(VF)

Very

low

frequency

(Vlf)

low

fr

equency (LF)

Voice Frequencies.

is

the

normal range of

mately 20 to 20.000 H t

Very Low Frequenc

and include the higher e

musical instruments ma

The VLF range is al

so

ple. VLF radio transmi'i

Low Frequencies.

L

mary communication


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communication over distances of m

the acoustical energy be converted isent over a transmission system of socomprises all of the frequencies orradiated, from the longest electricacosmic rays.

Public Switched Telephone Netwwidth in channels of 4 kHz, with 3 k


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40 FUNDAMENTALS OF TRANSMISSION S

f1


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TABLE 2.1 Frequency Spectrum

Band DesignationNominal

Frequency

Audible 20 Hz20 kHz Direct Current (DC) 030 Hz Extremely Low

Frequency (ELF)30300 Hz


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Freq Spectrum

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