ARLA/CLUSTER: Quem inventou o radioamadorismo.?

[João Costa > CT1FBF]

Who Invented Ham Radios

We have to go back in time to well over one hundred years ago to the
late 1880's to discover the early pioneers who first found that radio
waves actually existed.

Heinrich Rudolf Hertz a German Physicist was the man who conclusively
proved the existence that radio waves did actually exist; he was
driven by the theory which emanated from James Clarke Maxwell who
explored the electromagnetic theory of light.

Radio theory was further developed by Guglielmo Marconi in the 1890's
his works on radio waves were subsequently implemented into a system
of communication. History shows us that in the late 19th century keen
radio enthusiasts were interconnecting their own telegraphic
apparatus.

Many people began experimenting with this newly discovered area of
physics and the Hertzian waves as they became known. I experimented
with modulating a one Megahertz crystal commonly found on computer
mother boards. Modulating simply means to change the radio wave in
some special way. Amplitude modulation is produced when a microphone
changes the radio wave by changing the amplitude; this occurs when the
frequencies contained in the human voice alter the shape of the radio
signal, high peeks occur when high frequencies contained in the voice
are mixed with the carrier signal.

A radio wave is a form of electromagnetic radiation, whose source is
heat. A radio transmission contains two signals, the carrier signal or
carrier wave and the message signal, the message is superimposed on
the carrier wave using a microphone in Amplitude Modulation.
The amplitude message signal is recovered in a receiver by a diode;
the diode detects the voice signal which can then be listened to, with
the aid of a crystal earpiece.

A one megahertz transmitter outlined above is easily built and
provides a tangible demonstration of how radio works. Building a
simple T.R.F. or tuned radio frequency receiver will allow you to hear
your own voice. A crystal set is a type of T.R.F. receiver and is
easily built from a coil and variable capacitor. A diode or as it was
known, a cats whisker, is used in the crystal set circuit to detect
the audio produced from the microphone, a simple inexpensive high
impedance ear piece connected to the circuit will allow you to hear
the speech from your transmitter.

Magazines in the early 1900s produced many article about how to build
a radio and transmitter, including spark transmitters which spread
radio signals across a wide portion of the radio spectrum. I built
these simple spark transmitters in my early days when developing my
radio interest; they produced a lot of interference on our television
set. A small amount of power as I discovered would travel for a few
metres. Adding a length of wire crudely wrapped around the spark
transmitter increased the signal by many times. Motor bike spark plugs
produced a similar effect together with some types of early motor
cars; suppression techniques and the use of fibre optic cable to
propagate television signals have eliminated this type of
interference.

John G4YDM

http://g4ydm.blogspot.co.uk/

Article Source:
http://EzineArticles.com/expert/John_Allsopp/1925417

Article Source:
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