The Discoverer Of The Wireless Telegraphy English Language Essay

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Figure . Portrait of a young Guglielmo. Guglielmo Marconi was born in April, 25th in 1874 in a town called Bologna, Italy. Guglielmo was the second son of a wealthy (Italian) landowner and silk merchant. His mother was from an Irish descendant. Guglielmo received his early childhood schooling from private tutors until he attended the Livorno technical institute. The reason for his "home schooling" was that his family continually moved between Bologna, Florence and Livorno. Whilst growing up, he was fascinated by science and continually requested his tutors to elaborate on scientific areas of his studies. Discoveries in the field of electricity where of specific interest to him. http://newsletter.drachen.org/May2007/photos/GuglielmoMarconi.jpg

When Guglielmo was nearing university, Heinrich Hertz discovered proof to support the theory of electromagnetic radiation. This proved to be the major trigger for Guglielmo's interest in physics. This was therefore strengthened by the opportunity to briefly study and attend classes, with a physics lecturer, Augusto Righi. Augusto Righi was researching high frequency radio signals.

Guglielmo Marconi experimented on electromagnetic and payed special attention to the possibility of electromagnetic being used in telegraph. By the end of 1895 Guglielmo could detect wireless signals over a mile away and out of sight. Most other scientists could only transmit signals up to 100meters. During his work Guglielmo had two critical improvements. He increased the length of the transmitter and the receiver antennas. He also changed the orientation of dipole antennas from being horizontal to vertical. Therefore with these improvements, Guglielmo was able to reach distances of 1.5 km.

As Guglielmo had already discovered that he could wireless signals over a mile away and out of sight, he decided to research what kind of wave worked the best. He discovered that the use of surface waves meant that he could send radio signals over the crest of a hill therefore not limited to "line of sight" communication.

Guglielmo went to the Italian government, but was unable to interest them in the miracle of wireless. So at the age of 21 in the early 1896, he travelled to London where he received great interest from the British post office. Guglielmo had his first ever wireless communication over the open sea during 1897. The signal was sent over a distance of 6 km with the message of "are you ready?"

A fellow scientist, whose name was Preece, was so impressed that he introduced Guglielmo's work at 2 of his very important London lectures. Guglielmo now had international attention. In 1901 Due to this publicity the president of America, President Roosevelt sent a message of greeting to King Edward VII of the United Kingdom.

The most valuable feature of the new wireless telegraphy was the ability to provide communication where regular telegraph lines could not run. This proved useful to supply ship passengers' current news as they had no contact to the newspapers.

Guglielmo Marconi's experiment of creating, sending and detecting radio waves is relatively simple, not beyond the abilities of high school students. Marconi's radio equipment was limited by being essentially untuned, which greatly restricted the number of spark-gap radio transmitters which could operate simultaneously in a geographical area without causing mutually disruptive interference. In this patent, Marconi addressed this defect with a much more sophisticated design, which featured two tuned-circuits at both the transmitting and receiving antennas. (Below)

Marconi's Transmitter 1900

Marconi's Transmitter 1900

Marconi's Receiver 1900

Marconi's Receiver 1900

Diagram .Marconi's transmitter (Fig 1) and receiver (Fig 2), presented below, are taken from the US patent 763772 issued in 1904, and which was at the core of the litigation dispute of 1943.

The energy wave generated by a transmitter is called a radio wave. The radio wave radiated into space by the transmitting antenna is a very complex form of energy containing both electric and magnetic fields. Because of this combination of fields, radio waves are also referred to as electromagnetic radiation. The basic shape of the wave generated by a transmitter is that of a sine wave. The wave radiated out into space, however, may or may not retain the characteristics of the sine wave. A sine wave can be one cycle or many cycles.

The wave equation is an equation for an unknown function u(t, x) of the form

u_{tt} = c^2 u_{xx}. \,

u(0,x) = f(x), \,

u_t(0,x) = g(x), \,

The solution of this problem is given by d'Alembert's formula:

u(t,x) = \frac{1}{2} \left[f(x-ct) + f(x+ct)\right] + \frac{1}{2c}\int_{x-ct}^{x+ct} g(y)\, dy. \,

This formula implies that the solution at (t,x) depends only upon the data on the segment of the initial line that is cut out by the characteristic curves

x - ct = \hbox{constant,} \quad x + ct = \hbox{constant}, \,

That are drawn backwards from that point. These curves correspond to signals that propagate with velocity c forward and backward.

Modern Radio

Radio is the transmission of signals by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space.

Originally, radio or radiotelegraphy was called "wireless telegraphy", which was shortened to "wireless" by the British.

Radio systems used for communications will. With more than 100 years of development, each process is implemented by a wide range of methods, specialized for different communications purposes.

Early radio systems relied entirely on the energy collected by an antenna to produce signals for the operator.

Early uses were maritime, for sending telegraphic messages using Morse code between ships and land. One of the most memorable uses of marine telegraphy was during the sinking of the RMS Titanic in 1912, including communications between operators on the sinking ship and nearby vessels, and communications to shore stations listing the survivors.

Radio was used to pass on orders and communications between armies and navies on both sides in World War I. Today, radio takes many forms, including wireless networks and mobile communications of all types, as well as radio broadcasting.

Satellite Radio, MP3 files, RealAudio, WI-Fi, Broadband, Cell Phone Radio, Podcasting and Wi-Max are all things that have come around due to the wonderful discovery of radio waves and the wireless radio. Satellite -launched on September 25, 2001. MP3 files - The first software encoder/player was released to the public in July, 1995. The Significance is that this format shrunk the size of large audio files while maintaining fidelity. RealAudio - Introduced in 1995 by RealAudio. The Significance of RealAudio broke the second "sound barrier" by creating the illusion of a "Radio" transmission while maintaining some modicum of fidelity Wi-Fi -The technology of how wireless local area networks operate. Its Significance of Wi-Fi demonstrated the promise of how Internet Radio might someday make the jump from computers to mobile devices. Broadband provided the "power" Internet Radio needed to evolve from choppy and "buffering" audio to continuous streams of higher fidelity. Cell Phone Radio Significance because the cell phone is the one product most poised to eventually carry all our audio and video content.

With our modern and ever changing world, we can work out all the equations that go with radios. Wavelength and frequency, band conversions, ohm's law, power, impedance, resonance, Transformers, inductors, and toroids, SWR, RMS, PEP, Decibels and Propagation are all the different equations that can be used when dealing with radios.

\lambda = \frac{c}{f}

Frequency (MHz) to wavelength (m)

300 / MHz = m

Here we can work out the frequency therefore work out the wavelength.

Ohm's law, power, impedance

V = IR

P = IV = I2R

Z_C = \frac{-1}{\omega C}

ZL = ωL

ω = 2πf

Series resistance adds

Two parallel resistances: R_1||R_2 = \frac{R_1R_2}{R_1+R_2}

Multiple parallel resistances: R_1||...||R_n = \frac{1}{\frac{1}{R_1}+...+\frac{1}{R_n}}

Parallel combinations of reactance's

Time constant with these radio equations can become very simple.

Current / voltage lead/lag with reactance

Resonance

f = \frac{1}{2 \pi \sqrt{LC}}

\omega = \frac{1}{\sqrt{LC}}

Quality:

Q = \frac{f}{BW} = \frac{V_Z}{V_R}

BW = fhigh − flow

V = VieT / Ï„

Transformers, inductors, and toroids

L = \frac{ A_L N^2}{10000}

Where: L = inductance in μH

AL = inductance index in μH / 100 turns

N = number of turns

SWR, RMS, PEP

V_{rms} = \frac{V_{peak}}{ \sqrt 2} \approx 0.707\ V_{peak}

Decibels

dB = 10 \log \frac{A_1}{A_2}

Propagation

VHF propagation via ground wave propagation is limited by line of sight with some refraction towards the earth. Thus, your maximum distance is limited by the curvature of the earth. According to the Antenna Book (19th Ed, p23-5) the radio horizon is

D = C \sqrt{H}

Where D is distance, H is height, and C is

C

D units

H units

1.415

miles

feet

4.124

km

meters

This equation is an approximation for VHF that combines the exact geometric relation with the offset for refraction. The amount of refraction changes with frequency making this equation less accurate outside of vhf.

An alternate equation calculates the horizon vs. frequency based on where diffraction effects take over and weaken your signal:

D_{km} = \frac{80}{\sqrt[3]{f_{MHz}}}

Resources

Books

Bray, J. The Communications Miracle. New York: Plenum, 1995

Bussey, G. Marconi's Atlantic Leap. Coventry: Marconi Communications, 2001

Garratt, G. R. M. The Early History of Radio from Faraday to Marconi. London, IEE, 1993

Marconi, D. My Father, Marconi. Toronto: Guernica Editions Inc., 2nd edn, 1996

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