Radio waves are a type of electromagnetic radiation that have wavelengths in the electromagnetic spectrum. They can travel at the speed of light and have different frequencies and propagation properties depending on their wavelength. Radio waves were first predicted by Maxwell and demonstrated by Hertz in the late 1800s. They are now used for various technologies like radio, television, wireless networks, GPS, and more. International organizations like ITU regulate radio wave usage through frequency allocation and regional guidelines.

1. Radio Waves
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2. Radio Wave
• Radio Waves are type of electromagnetic radiation, they
have wavelengths in the electromagnetic spectrum.
• Radio wave frequencies varies from 300 GMz to as small as 3KHz.
• Radio wave travels at the speed of light.
• wave have different frequencies when in the earths atmosphere,
long wave lengths cover a part of the earth constantly and reflect
off the ionosphere and then travel around the world.
• Shorter wavelengths bend very little and travel on a line of a
sight meaning that if there are buildings etc. in the way then
the signal could be badly effected.

3. History: How Radio Wave Came?
• Radio waves were first predicted by mathematical work done in 1867 by Scottish
mathematician physicist James Clerk Maxwell & he noticed waves like light and
similarities in electrical and magnetic observations. Maxwell described light waves
and radio waves as waves of electromagnetism that travel in space, radiated by a
charged particle as it undergoes acceleration.
• In 1887 Heinrich Hertz demonstrated the reality of Maxwell's electromagnetic
waves by experimentally generating radio waves in his laboratory, showing that
they exhibited the same wave properties as light, standing waves, refraction,
diffraction and polarization.

4. Characteristics of Radio Waves
1. Radio Wave's Directness
• As a frequency gets higher, the wave length gets shorter, and
the directness and refractiveness increase, It approaches the
properties of light.
2. Noise Occurrence
• When a radio wave is weak, (when the electric signal is small),
noise increases. For example, the further the distance between
the base unit and the portable unit (inverse proportion to
distance squared), the radio wave will become weaker and, at a
certain level, the noise (radio wave disturbance). There is also
the possibility that the cordless phone may receive interference
when operated near aradio or TV station, electric cable, etc.

5. Radio Wave Propagation
1-Radio Waves propagate outward from an antenna , at the speed
of light. The exact nature of these waves is determined by the
transmission medium. i.e., In free space they travel in straight
lines , whereas in the atmosphere they generally travel in curved
path.
2-In a unguided medium, radio waves propagate in TEM mode
while in confined or guided medium radio waves do not
propagate in the TEM mode but in TM or TE mode.
3- Radio waves can be reflected and refracted in a manner similar
to light . They are effected by ground terrain, atmosphere and
other objects.

6. DIFFERENT MODES OF PROPAGATION
Gr
Radi
ound waves Space w
of Si
o waves
aves or Line
ght waves
Direct waves
Ground refle ted waves
Sky waves
MODES OF PROPAGATION FREQUENCY APPLICATION
1. Ground waves VLF
LF
MF
1.Submarine Communication
2.AM ,FM and television
broadcasting
2. Space or line of sight waves HF
VHF
UHF
1.Satellite communication
2.Mobile communication
3. Sky waves 2Mhz-30Mhz c1.Microwave link
2.Radar communication

7. GROUND WAVE
PROPAGATION
It propagates from transmitter to receiver by gliding over the surface of the earth in
which both antennas are close to the surface of the earth. It follows the curvature
of the earth.
Earth is assumed to be an ideal conductor ,EM waves cannot penetrate ideal
conductor only exist in dielectric medium above conducting surface that’s why
ground wave propagation is possible.
The Ground waves are traverse in nature. Horizontal polarised antennas are not
preferred as the horizontal component of the electric field in contactwith the earth is
short circuited by the earth.

8. WAVE TILT
The earth is not an ideal conductor , so there will remain a tangential component of
electric
field resulting wave tilt.
The earth is characterised by σ and εr then Surface impedanc for
earth:
Intrinsic impedance for dielectric medium:
Since there is surface impedance which is non-zero there will be tangential component
of electric field i.e., EH and Evbe vertical component of electric field and if H is the
magnetic field
then, and

9. Then,
From the equation we see that the two component are not in phase and
as in general
The resultant electric field is elliptically polarised with plane of
polarisation in longitudinal direction .as conductivity is infinite for
ideal conductor the wave is vertically polarised as the conductivity
decreases the ellipse become more tilted. This phenomena is known
as WAVETILT.
wave tilt for decreasing value of
conductivity

10. Classification of Radio wave
spectrum

11. Classified by Bands, Frequency range, &
Wavelength
1.Low to Medium Frequencies
2.Higher Frequencies
3.Shortwave Radio
4.Highest Frequencies
5.Astronomical Sources

12. Classification of Radio Wave
Band Frequency Wavelength
Extremely Low
Frequency(ELF)
<3 khz >100km
Very Low Frequency(VLF) 3-30 hz 10-100krn
Low Frequency(LF) 30-300 khz 1-10km
Medium Frequency(MF) 300khz-3mhz 100m-1km
High Frequency(HF) 3-30mhz 10-100m
Very High Frequency(VHF) 30-300mhz 1-10m
Ultra High Frequency(UHF) 300mhz-3Ghz 10cm-1m
Super High Frequency(SHF) 3-30Ghz 1-10cm
Extremely High
Frequency(EHF)
30-300Ghz 1mm-1cm

13. Authority Guideline and Regulation of
Radio Wave (reference: ITU-R)
• Spectrum cannot be confined to a given territory
• RR (Radio Regulation) is an international treaty and should be considered
by national administrations
• Stations should be duly registered to be protected
• International harmonization brings many advantages for Administrations
• (facilitates coordination, roaming, allows for economies of scale)
• Enables recognition of spectrum uses and their protection against harmful
interference, at national and international level
• Stations shall be duly registered, with the technical parameters
• Bands designated for industrial, scientific and medical (ISM) applications
• Bands designated for use by high altitude platform stations
• Bands identified* for use by high-density applications in the fixed satellite
service
• Bands identified* for International Mobile Telecommunications (IMT)

14. Spring 2006 UCSD: Physics 8; 2006 14
Encoding Information on Radio Waves
• Two common ways to carry analog
information with radio waves
– Amplitude Modulation (AM)
– Frequency Modulation (FM): “static free”

15. UCSD: Physics 8; 2006 15
AM Radio
• Amplitude Modulation (AM) uses changes
in the signal strength to convey information
pressure modulation (sound)
electromagnetic wave
modulation

16. UCSD: Physics 8; 2006 16
FM Radio
• Frequency Modulation (FM) uses changes
in the wave’s frequency to convey
information
pressure modulation (sound)
electromagnetic wave
modulation

17. Real Life association of Radio Waves:
Radio Waves were discovered in 1887.However, as time went on people
started to take radio waves for granted and now hardly anyone realizes how
much we actually use radio waves in our everyday’s lives. The biggest use for
radio waves are given bellow
• Televisions
• Wireless Network
• Mobile Phone
• GPS System
• Radio Controlled Toys

18. Radio Astronomy
A radio telescope is simply a telescope
that is designed to receive radio waves
from space. In its simplest form it has
three components:
One or more antennas to collect the
incoming radio waves. Most antennas are
parabolic dishes that reflect the radio
waves to a receiver, in the same way as a
curved mirror can focus visible light to a
point. Antennas can be other shapes
however. A Yagi antenna, similar to that
used for TV reception, can be used for
radio astronomy as was the case in the
early Dover Heights telescopes.
A receiver and amplifier to boost the very
weak radio signal to a measurable level.
These days the amplifiers are extremely
sensitive and are normally cooled to very
low temperatures to minimize
interference due to the noise generated
by the movement of the atoms in the
metal.
A recorder to keep a record of the signal.
In the early days of radio astronomy this
was normally a chart recorder that drew a
graph on paper in ink. Most radio
telescopes nowadays record directly to
some form of computer memory disk as
astronomers use sophisticated software
to process and analyze the data.

19. Use mechanism followed by the guidelines of
(ITU)
To have at least some success in worldwide coordination and to
reflect national interests, the ITU-R has split the world into three
regions:
– Region 1 covers Europe, the Middle East, countries of the
former Soviet Union, and Africa.
– Region 2 includes Greenland, North and South America, and
– Region 3 comprises the Far East, Australia, and New Zealand.
• Within these regions, national agencies are responsible for further
regulations, e.g., the Federal Communications Commission (FCC)
in the US.
• Several nations have a common agency such as European
Conference for Posts and Telecommunications (CEPT) in Europe.
• To achieve at least some harmonization, the ITU-R holds, the World
Radio Conference (WRC), to periodically discuss and decide
frequency allocations for all three regions.

20. Frequencies for radio transmission

21. Harmful Effects of Radio Waves
• If RF radiation is absorbed by the body in large enough
amounts, it can produce heat. This can lead to burns and body
tissue
•
• Higher frequency of radio wave are the cause of heart attack
and tissue cancer
• Human body temperature increases when radio wave devices
are close
•
• changes in the growth of certain plant cells for RF radiation
•
• RF radiation is also responsible for global warming

22. Conclusion:
The prime purpose of radio is to convey information from one place to
another through the intervening media (i.e., air, space, nonconducting
materials) without wires. Besides being used for transmitting sound and
televisions signals, radio is used for the transmission of data in coded form. In
the form of radar it is used also for sending out signals and picking up their
reflections from objects in their path. Long-range radio signals enable
astronauts to communicate with the earth from the moon and carry
information from space probes as they travel to distant planets For navigation
of ships and aircraft the radio range, radio compass (or direction finder), and
radio time signals are widely used. Radio signals sent from global positioning
satellites can also be used by special receivers for a precise indication of
position.

23. References
• Radio waves introduction & history
https://en.wikipedia.org/wiki/Radio_wave#:~:text=Radio%20waves%20were%20fi
rst%20predicted,mathematical%20physicist%20James%20Clerk%20Maxwell.&text
=Italian%20inventor%20Guglielmo%20Marconi%20developed,physics%20for%20hi
s%20radio%20work.
• Radio waves propagation https://www.electronics-notes.com/articles/antennas-
propagation/propagation-overview/basics.php
• Classification of Radio Waves https://en.wikipedia.org/wiki/Radio_wave
• International guidelines for radio waves https://www.itu.int/dms_pub/itu-
r/md/15/wrs16/sp/R15-WRS16-SP-0003!!PDF-E.pdf
• Real life association & radio astronomy https://www.britannica.com/science/radio-
wave
https://www.atnf.csiro.au/outreach/education/everyone/radio-
astronomy/index.html#:~:text=A%20radio%20telescope%20is%20simply,receive%20ra
dio%20waves%20from%20space.&text=One%20or%20more%20antennas%20to,visibl
e%20light%20to%20a%20point.