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Anyone involved with the various applications of radio would do well to take a basic radio course.  Radio is the communication between
two or more points by way of electromagnetic transmission.  Although radio is a part of many inventions, its basic concept of transmitting
and receiving audio signals remains the same.  Some of the many uses began with the military, followed by police and fire, aviation and marine,
AM and FM broadcasting, television, shortwave, radar and space communications, satellite relaying, weather reporting, and cellular telephones.

How was Radio invented ?

It is generally observed that Radio was first "planned on paper", or conceived, by James Clerk Maxwell's field equations giving a physical basis for
the electromagnetic spectrum.  Not long after, Heinrich Hertz showed the existence of radio waves over a long distance, and in 1909 Guglielmo
Marconi was awarded the Nobel Prize for developing wireless telegraphy by sending a long-wave radio signal across the Atlantic Ocean.

What are "radio waves" ?

Energy is required to create a radio signal.  Electric charge is accelerated in a transmitting antenna which carries this energy to a receiving antenna.
Only a small fraction of the transmitter power is normally received by the receiving antenna but can be electronically amplified upto millions of times
as needed.

Radio waves are defined in a like manner as other waves such that a sinusoidal pattern is referred to describing its wavelength, frequency, and
amplitude.  From peak to peak gives its wavelength, the reciprocal gives the frequency, and height the amplitude.

Radio waves with short wavelengths travel in a straight line while long wavelengths can follow the curvature of the earth.  A radio signal with an
intermediate wavelength can reflect off an atmospheric layer high above the earth, called the ionosphere.  These are called skywaves.

The ionosphere is renewed each day when the sun's radiation ionizes atoms in rarefied air at heights of 25 to 200 miles.  When skywaves reflect
from the higher layer of the ionosphere (called the F layer) it is said to act as a radio mirror, bouncing skywaves back to earth far from their source.

Long distance radio signal propagation depends on the conditions of the sun, including an 11-year solar sunspot cycle.  When sunspots are large (cooler
areas of the sun) the sun is more effective in building the radio ionosphere.  When a solar flare bombards the earth's magnetic field, it causes nearly
a complete loss of skywave radio propagation.  Microwaves, however, are exempt from this disturbance which do not rely on ionospheric reflection.

On the other hand, FM broadcasts are seldom heard beyond the horizon, deliberately chosen so as not to reflect from the sky.  They possess a higher
frequency range and are received as direct waves, allowing frequency assignments to be duplicated in cities of fairly close proximity without

Shortwave radio is considered unique in that it will change frequency as the 11-year sunspot cycle waxes and wanes.  Shortwave stations around the
world move to shorter wavelengths when there are more sunspots and to longer wavelengths when there are less. This is to take advantage of the
changing ionosphere.

How do radio waves go through building walls, and what blocks radio waves ?

It is better to think that radio waves "go around" the walls of a building, or your home, rather than through them.  This is because the wavelength of
radio waves are too large to interact with a structural wall.  On the other hand, visible light has wavelengths on a similar scale as a building and therefore
get blocked.  On the other end of the spectrum, gamma rays are so small that they actually do go through the walls because of the interatomic spacing.
If walls are very thick however, such as in cave or tunnel, this will approach the scale of a radio wave and they will soon become blocked.

In these examples, it is sometimes helpful to think of an analogy of an ant next to an elephant.  To the ant, the elephant is so big it doesn't even see
the elephant, and to the elephant the ant is so small it completely ignores it.  The elephant is the radio wave that passes by the ant because it doesn't
even know it is there.

Does water block radio waves ?

Similar in behavior to other types of waves, the transmission of a radio wave can either transmit, reflect, or become absorbed by an opposing medium.

If we go back to the above analogy with the ant versus the elephant, we can add one more aspect to the scenario where the elephant isn't totally oblivious
to the ant.  It is somewhat aware that the ant is there but goes around it because it will not be in its way - that is, if the ant represents a building or a wall.
A radio wave does sense an opposing medium, but depending on what it is, can either go around it or not.  If the medium is a body of water, by the time
the radio wave has sensed what the medium is, it has become absorbed by it. It's a little bit like the blackhole effect.  Before the radio wave has a chance
to decipher what is confronting it, it immediately becomes absorbed by the water.  That is why sea ships and submarines use sonar to check their depth
and not radio.  Radio communication, however, is well open over the surface of the water to other ships or land-based stations.

How is water beneficial ?

Water is thought to be a life element of the universe. Where there is water there is a good chance of existing life. That is why space explorers search for
water (or ice) among the moons and planets throughout the cosmos.  Water on earth is quite obvious.  Its composition is very high in a human. We would
die without water.  Almost everything is cleansed with water, including us, what we eat, our kitchens and houses, and even cuts and wounds.  In this
sense water is also considered a purifying element.

What does water have to with radio ?  For the most part, nothing; other than our oceans can absorb any excess radio waves considered stray over the earth.
In other words, it can eliminate "radio pollution" if there is indeed any excess radio waves that are unwanted.  Most transmitted radio waves are never
harmful to the human, but who knows what accumulates in the vast complexity and number of inventions incorporating radio, and if there are any
"unknown" signals coming from outer space (such as from another civilization from another planet).  The vast bodies of ocean water can clean all that up
and raise the water temperature just a fraction of a centigrade.  That should make you feel better.

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