Collaborating with suppliers can help improve inventory management through better communication, information sharing, and coordinated planning. This can lead to reduced lead times, improved quality, and lower costs.

1. Unguided (Wireless) Media
Unguided media transport electromagnetic waves without using a
physical conductor.
 This type of communication is often referred to as wireless
communication.
Signals are normally broadcast through free space and thus are
available to anyone who has a device capable of receiving them.

3. Cont.….d
Unguided signals can travel from a given source to its destination in
several ways:
1. ground propagation
2. sky propagation
3. line-of-sight propagation.

4. Ground propagation
In-ground propagation, radio waves travel through the lowest portion
of the atmosphere, hugging the earth.
These low-frequency signals emanate in all directions from the
transmitting antenna and follow the curvature of the planet.
Distance depends on the amount of power in the signal.
The greater the power, the greater the distance will be.

5. sky propagation
• In sky propagation, higher-frequency radio waves radiate upward into
the ionosphere (the layer of the atmosphere where particles exist as
ions) where they are reflected on earth.
• This type of transmission allows for greater distances with lower
output power.

6. line-of-sight propagation
• line-of-sight propagation, very high-frequency signals are transmitted
in straight lines directly from antenna to antenna.
• Antennas must be directional, facing each other and either tall enough
or close enough together not to be affected by the curvature of the
earth.
• Line-of-sight propagation is tricky because radio transmissions cannot
be completely focused.

7. A. Radio Waves
Radio waves have frequencies between 3 kHz and 1 GHz, while microwaves range
from 1 to 300 GHz.
The behavior of the waves, rather than the frequencies, is a better criterion for
classification.
Radio waves are omnidirectional, meaning they propagate in all directions.
Antennas transmitting radio waves do not need to be aligned with receiving antennas.
The omnidirectional property allows radio waves to be received by any compatible
antenna.
However, the omnidirectional nature also makes radio waves susceptible to
interference from other antennas using the same frequency or band.
Radio waves, especially those propagated in the sky mode, can travel long distances.
This long-distance propagation makes radio waves suitable for AM radio and other
forms of long-distance broadcasting.

8. Omnidirectional Antenna
Radio waves utilize omnidirectional antennas that transmit signals in all
directions.
Different types of antennas are used based on the wavelength, signal strength,
and transmission purpose.
The omnidirectional nature of radio waves is advantageous for multicasting,
where one sender can reach multiple receivers.
Examples of multicasting applications include AM and FM radio, television
broadcasting, maritime radio, cordless phones, and paging systems.

9. Microwaves
Microwaves are a line-of-sight wireless communication technology that uses
high-frequency radio waves.
They provide high-speed wireless connections for voice, video, and data
transmission.
Microwaves are unidirectional, meaning they are transmitted in a narrowly
focused beam.
Both the sending and receiving antennas need to be aligned for successful
communication.
The unidirectional property allows multiple pairs of aligned antennas to
coexist without interference.
Microwaves are often used in point-to-point communication links, such as
microwave backhaul for cellular networks or wireless Internet service
providers.

10. Unidirectional Antenna
• Microwaves need unidirectional antennas that send out signals in one
direction.
• Two types of antennas are used for microwave communications:
A. parabolic dish
B. horn

11. parabolic dish antenna
A parabolic dish antenna is designed based on the geometry of a
parabola.
The parabolic shape ensures that every line within the dish is parallel
to the line of sight.
The curves of the parabola intersect at a common point called the
focus.
The dish acts as a funnel, capturing a wide range of waves and
directing them to the focus.
By focusing the waves at a single point, a parabolic dish antenna can
recover more of the signal compared to a single-point receiver.
Parabolic dish antennas are commonly used for long-range
communication, such as satellite communication and wireless Internet
service providers

12. horn antenna
• A horn antenna has a shape resembling a large scoop.
• Outgoing transmissions are broadcast up a stem or handle of the horn.
• The curved head of the horn antenna deflects the outgoing transmissions into
narrow parallel beams.
• Received transmissions are collected by the scooped shape of the horn.
• Similar to a parabolic dish antenna, the collected signals are deflected down into
the stem of the horn antenna.
• Horn antennas are used for both transmitting and receiving signals.
• They are commonly employed in applications such as radar systems, satellite
communication, and microwave links.