First of all am going to talk about my first place in
training field in ministry of telecommunication located in
Tahreer tower section related with sea communication
media, it’s simply summarized with three points which is:
1- telecommunication
2- wireless communication (radio transfer)
3- maritime communication
And telecommunication used three stacked beams
which are:
1- VHF 40 KM (receive+ transit)
2- MF 150 KM
3- HF up to 500 KM
MF, HF we cannot send the signal in the same place
because of the frequency it’s closed to each other
Mf telegraphy HF telegraphy
And now am going to write about the VHF in simple way:
The VHF used for the transmitter receiver systems and
the whole system divided to: voice power equipment,
filter, modulator, power amplifier and antenna.
It used for sea navigator to know the ship situation and
it helps the people to contact each other easily from the
sea to the land.
Telecommunication in a public way it applied to people
telephone, telex and telegraph services.
All of us know the systems that connected with
telecommunication which are: transmitter receiver,
battery (for emergency), computer, DSC, GMDS.
Discussion:
The system name: Trans. Receiver (com 160 STRC shore
trans. Receiver).
General use of the system:
1- Transmit VHF frequency to the ship.
2- Receive VHF frequency to the ship.
The system block diagram:
Radio:
1- voice processor: process voice
2- filter: it filters the signal and separate the
noise from it
3- amplifier: it amplifies the power for the
antenna
4- modulator: it controls the signal
5- molt diplex: it separate the signals
6- antenna: it receives the signal
DSC:
Operate under channel 70 and safety environment.
1- CPU: resolves the information.
2- LAN: it connect computers together in one
network
3- Alarm: it notice us if there is problem in the
device (light turn on)
4- Serial input-output: this part used to transfer
information
5- DSC: this is the only part related with
communication and it’s received information
6- Parallel input-output: it sent the information to
the printers
Maintenance procedure:
The principle to be used and to reduce the situation is by
having the calculation:
1- MTTF: main time to the furrier
2- MTTR: main time to repair
Type of the maintenance:
1- preventive of the maintenance
2- periodical maintenance
Preventive maintenance:
1- we have to clean the devices from dust
2- saving the voltages
3- it must be someone professional to repair the
device
Periodical maintenance:
1- everything related with the weather
2- it must to check on the device every week
Common faults:
1- it possible to have problem in the CKT like open
CKT or short CKT
2- it might the component burn
3- or it might be problem with cables
4- it might be something wrong with the equipment
Trouble shooting:
1- if there is something wrong we fix it
2- it must someone professional work on it
Calibration:
1- frequency generator
2- frequency-power measuring device
Conclusion:
I have gained a lot of information that was missing in
the college; in the training field they talk about the
telecommunication more expansion with details
And with more devices we see it explain the information
we study about it and now we are more experience
Microwave:
For the second three weeks we spent in Tahreer tower
with different section called microwave section, so am
going to talk about It in brief way:
Microwaves have wavelengths that can be measured in
centimeters!
Microwaves are good for transmitting information from
one place to another because microwave energy can
penetrate haze, light rain and snow, clouds, and smoke.
Shorter microwaves are used in remote sensing. These
microwaves are used for radar like the doppler radar
used in weather forecasts. Microwaves, used for radar,
are just a few inches long.
This microwave tower can transmit information like
telephone calls and computer data from one city to
another.
Microwave definition:
Transfer information point to point
The important part in the microwave it’s the dish
There are three frequencies:
1- surface wave
2- space wave
3- sky wave
A typical digital microwave radio consists of three
basic components:
1- A digital modem unit
2- An RF unit
3- Parabolic”dish” antenna
There are kinds of antenna:
1- solid
2- mesh
There are three kinds of feeders:
1- receiver
2- receiver + transfer
3- transfer
There are two needles in the feeder it used for
polarization that’s why it called dull the first needle it
receives only vertical signals and the other needle it
receives only horizontal signals
Comparison of FM with AM:
Advantages over AM:
1- better SNR, and more resistant to noise
2- efficient- less power is required to angle modulate
3- capture effect reduces mutual interference
Disadvantages:
1- much wider bandwidth is required
2- slightly more complex circuitry is needed
The dish depends on three things:
1- power
2- frequency
3- distance
Satellite:
Next sixth week we went to the Kaifan central, there we
learn about satellites with ENG. Fozi
The troubles satellites face it:
1- sun winds
2- rain
3- dust
4- stars falling
Intel sat:
The International Telecommunications Satellite
Organization (ITSO) is the world's largest commercial
satellite communications services provider. It is an
international consortium that owns and manages a
constellation of communications satellites (Intel sat) to
provide international broadcast services>
At the end we went to Kaifan Central and he memorize
what we have taken in the last weeks
Remarks:
In the first day of training field we go to tahreer tower
section maritime, and Eng. Salem bahbahani he was our
advisor in the first three weeks there, he teach us about
telecommunication with more details and in a simple way,
and he started with noise and how to wangle from it.
He begins with telecommunication definition:
It’s the relation between time and wave.
After that he talks about the noise and it’s the worst
enemy to the telecommunication, there is two reasons of
noise one of them it causes by the devices and the other
reason the weather that the information transfer
through it .
The relation between the frequency and wavelength
Wavelength= 1/ frequency
After that he speaks about modulation and how it
effects to the noise, the modulation it controls the noise
by raising the signal and there are three types of
modulation:
1- FM
2- AM
3- Pulse code modulation (PCM)
4- CDM
5- TDM
6- FDM
7- GSM
And it must to be there kind of filters; even filters got a
different type:
1- High pass frequency
2- Low pass frequency
3- Band pass frequency
He shows us the difference between bandwidth and beam
width, the bandwidth it used for the frequency and the
beam width used for the antenna
So here we go in a simple way am going to write about
each part the eng. Talks about in three weeks.
Noise:
In common use the word noise means unwanted sound or
noise pollution. In electronics noise can refer to the
electronic signal corresponding to acoustic noise (in an
audio system) or the electronic signal corresponding to
the (visual) noise commonly seen as 'snow' on a degraded
television or video image. In signal processing or
computing it can be considered data without meaning;
that is, data that is not being used to transmit a signal,
but is simply produced as an unwanted by-product of
other activities. In Information Theory, however, noise is
still considered to be information. In a broader sense,
film grain or even advertisements in web pages can be
considered noise.
Noise can block, distort, or change the meaning of a
message in both human and electronic communication.
In many of these areas, the special case of thermal noise
arises, which sets a fundamental lower limit to what can
be measured or signaled and is related to basic physical
processes at the molecular level described by well known
simple formulae.
Signal classification:
Signals can be either analog or digital, and may come
from various sources.
There are various sorts of signal processing, depending
on the nature of the signal, as in the following examples.
For analog signals, signal processing may involve the
amplification and filtering of audio signals for audio
equipment or the modulation and demodulation of signals
for telecommunications. For digital signals, signal
processing may involve the compression, error checking
and error detection of digital signals.
Digital:
A digital system is one that uses discrete values (often
electrical voltages), representing numbers or non-numeric
symbols such as letters or icons, for input, processing,
transmission, storage, or display, rather than a
continuous range of values (ie, as in an analog system).
The distinction between "digital" and "analog" can refer
to method of input, data storage and transfer, or the
internal working of a device. The word comes from the
same source as the word digit and digitus: the Latin word
for finger (counting on the fingers) as these are used for
discrete counting.
The word digital is most commonly used in computing and
electronics, especially where real-world information is
converted to binary numeric form as in digital audio and
digital photography. Such data-carrying signals carry one
of two electronic or optical pulses, logic 1 (pulse present)
or 0 (pulse absent).
The question is why do we convert from analog to digital?
Answers:
1- less noise
2- less time
3- less power we use
4- more information
5- less maintenance
All of us know that the worst thing in digital is the
bandwidth too large.
Where do we use telecommunication?
1- In the space
2- In the sea
3- Ship
4- Planes
5- Internet
6- Fax
7- Cars
8- Fiber optics
Cables:
A cable is one or more wires or optical fibers bound
together, typically in a common protective jacket or
sheath. The individual wires or fibers inside the jacket
may be covered or insulated. Combination cables may
contain both electrical wires and optical fibers. Electrical
wire is usually copper because of its excellent
conductivity, but aluminum is sometimes used because it
costs less
There are various types of cables:
1- twisted cable : shield- un shield
2- fiber
3- hub cable
Radio regulation definition:
The allocation of different frequency bands to different
radio services.
Microwave:
Microwaves are electromagnetic waves with wavelengths
shorter than one meter and longer than one millimeter, or
frequencies between 300 megahertz and 300 gigahertz.
(UHF, SHF, EHF).
Ariel:
In a brief way the Ariel receive and transfer signals
from satellite to different devices.
Even Ariel got various types:
Dish-patch-yagi-dipole-rombic-T
Telecommunication units:
dB-dBm-dBm0-dBr-dBv-dBm0p-dBI-dVBmrms-dVBp-p
Attenuator:
Low level attenuators
An attenuator is effectively the opposite of an amplifier,
though the two work by different methods. While an
amplifier provides gain, an attenuator provides loss, or
gain less than 1.
Power attenuators
In audio electronics, attenuators are used as a dummy
load by sending all of the power to the resistor and none
to the speaker, in order to silence or reduce the output
volume of an audio amplifier (for example, a guitar
amplifier). Silencing an amplifier is useful for biasing the
positive and negative signal crossover, for running bench
tests such as measuring the amplifier's maximum output
wattage, and for adding line-level effects between a
guitar amplifier and a guitar speaker.
Optical fibers:
An optical fiber is a glass or plastic fiber designed to
guide light along its length. Fiber optics is the overlap of
applied science and engineering concerned with the
design and application of optical fibers. Optical fibers
are widely used in fiber-optic communication, which
permits transmission over longer distances and at higher
data rates than other forms of communications. Fibers
are used instead of metal wires because signals travel
along them with less loss, and they are immune to
electromagnetic interference. Optical fibers are also
used to form sensors, and in a variety of other
applications.
Light is kept in the "core" of the optical fiber by total
internal reflection. This causes the fiber to act as a
waveguide. Fibers which support many propagation paths
or transverse modes are called multimode fibers (MMF).
Fibers which support only a single mode are called
singlemode fibers (SMF). Multimode fibers generally
have a large-diameter core, and are used for short-
distance communication links or for applications where
high power must be transmitted. Singlemode fibers are
used for most communication links longer than 200
meters.
Joining lengths of optical fiber is more complex than
joining electrical wire or cable. The ends of the fibers
must be carefully cleaved, and then spliced together
either mechanically or by fusing them together with an
electric arc. Special connectors are used to make
removable connections.
Buffer:
In telecommunication, a buffer is a routine or storage
medium used in telecommunications to compensate for a
difference in rate of flow of data, or time of occurrence
of events, when transferring data from one device to
another.
Buffers are used for many purposes, such as
(a) interconnecting two digital circuits operating at
different rates,
(b) holding data for use at a later time,
(c) allowing timing corrections to be made on a data
stream,
(d) collecting binary data bits into groups that can then
be operated on as a unit,
(e) delaying the transit time of a signal in order to allow
other operations to occur.
Radar:
Radar is a system that uses electromagnetic waves to
identify the range, altitude, direction, or speed of both
moving and fixed objects such as aircraft, ships, motor
vehicles, weather formations, and terrain. A transmitter
emits radio waves, which are reflected by the target and
detected by a receiver, typically in the same location as
the transmitter. Although the radio signal returned is
usually very weak, radio signals can easily be amplified.
This enables a radar to detect objects at ranges where
other emissions, such as sound or visible light, would be
too weak to detect. Radar is used in many contexts,
including meteorological detection of precipitation, air
traffic control, police detection of speeding traffic, and
by the military. It was originally called RDF (Radio
Direction Finder) in Britain. The term RADAR was coined
in 1941 as an acronym for Radio Detection and Ranging.
The term has since entered the English language as a
standard word, radar, losing the capitalization in the
process.
Digital Selective Calling Radios
Digital Selective Calling (DSC) radio is the latest in
marine radio technology. Digital Selective Calling is part
of a global upgrade in maritime distress communications.
Satellite and digital technology used for several years on
commercial ships is now available to the recreational
boater. DSC radios allow boaters to make ship-to-ship
private calls and the DSC distress channel is currently
being monitored by commercial ships.
The major advantage of the DSC radio is its ability to
send an automatic "mayday" that identifies the vessel
and also, when connected to a LORAN or GPS, can send
the vessels location. The DSC radio operates much like an
EPIRB that sends encoded "maydays" directly to
satellites. The DSC radio will also continue sending the
emergency signal if the skipper is disabled.
Another feature of the DSC radio is the ability to place
private ship-to-ship calls to other vessels equipped with
DSC radio. Basically if you know the MMSI number of the
radio you are calling only that vessel will receive you
message. Just like using your cell phone.
Although commercial ships over 300 tons are now
required to monitor the DSC Radio reserved Channel 70
for distress calls, the US Coast Guard is still monitoring
Channel 16. As the Coast Guard updates and upgrades
there equipment, they should be monitoring DSC Channel
70 in many areas by 2002-3 and be fully functional and
compliant by 2005-6. The USCG's equipment up grade will
include:
DSC capability to send or receive calls on channel 70
The DSC radio feature is part of the Global Maritime
Distress and Safety System (GMDSS).
DIGITAL
DSC uses a DIGITAL signal to send a specific set of
information. The information that can be passed by a
DSC call
How Radio Works:
"Radio waves" transmit music, conversations, pictures and
data invisibly through the air, often over millions of miles
-- it happens every day in thousands of different ways!
Even though radio waves are invisible and completely
undetectable to humans, they have totally changed
society. Whether we are talking about a cell phone, a
baby monitor, a cordless phone or any one of the
thousands of other wireless technologies, all of them use
radio waves to communicate.
Here are just a few of the everyday technologies that
depend on radio waves:
AM and FM radio broadcasts
Cordless phones
Garage door openers
Wireless networks
Radio-controlled toys
Television broadcasts
Cell phones
GPS receivers
Ham radios
Satellite communications
Police radios
Wireless clocks
The list goes on and on... Even things like radar and
microwave ovens depend on radio waves. Things like
communication and navigation satellites would be
impossible without radio waves, as would modern aviation
-- an airplane depends on a dozen different radio
systems. The current trend toward wireless Internet
access uses radio as well, and that means a lot more
convenience in the future!
The funny thing is that, at its core, radio is an incredibly
simple technology. With just a couple of electronic
components that cost at most a dollar or two, you can
build simple radio transmitters and receivers. The story
of how something so simple has become a bedrock
technology of the modern world is fascinating!
In this article, we will explore the technology of radio so
that you can completely understand how invisible radio
waves make so many things possible!
Problems encountered during field training system:
There is no board for lessons and there are no places for
the student
Suggestion to enhance future field training:
1- it must to be the training side more than the
theory
2- by giving us more time in training field
3- give us information could help us in the future
References:
www.Wikipedia.com , www.google.com, the images was
taking from the training field.