Mohammad Mijanur Rahman completed a one-year job attachment at the Mohakhali Standard-A Satellite Earth Station in Dhaka, Bangladesh. During this time, he was responsible for running international circuits and maintaining satellite communication equipment. In this report, he provides an overview of the earth station, including its satellite orbit and technical components. He also summarizes key aspects of satellite communication systems such as uplinks, downlinks, frequency bands, and antenna size. The knowledge and experience gained during his job attachment provided valuable practical training.

1. Bangladesh Telecommunications Company Limited
Telecom Training Center (TTC), Tejgaon, Dhaka
JOB ATTACHMENT REPORT
Date : From : 01-04-2010 To : 24-07-2011
Date of Submission : 25 July, 2011
Submitted To : Ms. Mst. Mallika Akar Khanom
Superintendent (Exam & Program),
TTC, Tejgaon, Dhaka.
Submitted By : Mohammad Mijanur Rahman
Roll No.01, Batch-TCM (Ext.)-09-10
TTC, Tejgaon, Dhaka.
Authorized Officer’s Signature : ...........................................

2. Job Attachment Report
On
“Mohakhali Standard-A Satellite E/S”
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Mohakhali Satellite Earth Station, Karail, Banani, Dhaka
At a glance Mohakhali Standard-A Satellite Earth Station
IOR (Indian Ocean Region) & GEO (Geostationary Earth Orbit) 64° East
C Band Carrier : works with INTELSAT
TX Frequency : 6 GHz
RX Frequency : 4 GHz
Antenna Size (Diameter) : 16 M
Antenna’s Weight : 35 tons
Total International Circuits : 5,000
Total Carriers : 30 with 12 countries
AZ : 230.77
EL : 049.55

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Methodology
Primary Source of Information:
Classes provided by concerned officer
Group discussion with colleagues
Relevant manual study on provided by the officers concerned
Secondary Source of Information:
Website of BTCL.
Annual Report of BTCL
Relevant books, Newspapers and Journals
Technical-related internet web sites
Lecture sheets provided by TTC’s honourable teachers

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On
“Mohakhali Standard-A Satellite E/S”
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Introduction
The first commercial communications satellite, INTELSAT (known as ‘Early
Bird’), was launched in April, 1965. Since then, Satellite communications have
become a major means for international as well as domestic communications
over long or moderate distances.
There are artificial man made satellite revolving around earth which help us to
communicate. In fact they help us in many ways. The television that we watch
and the internet that we browse all work through the satellite technology. The
technology is in fact used at all those places where the use of cables and wires is
practically impossible.
It first and most important applications was in inter country long distance
telephony. These satellite phones get connected directly through geostationary
satellite and then the signals are transmitted to teleport which is connected to a
satellite phone system. The technology is used in the regions or places where
the submarine communication cables and fiber optic cables are not possible.
In Bangladesh, Mohakhali Satellite E/S is playing a great role to expand new
circuits and carriers in tele-communication. Through this Satellite E/S along with
International Trunk Exchange, 30 carriers, 5000 international circuits are running
well with 12 countries. It is now also being used as stand by submarine
communication cables. This E/S is contributing greatly to revenue income of the
government.
The knowledge and experience which achieved in the field training in my job
area, here I have presented this with most key-points of satellite communication
system. I think it will fulfill the requirements of Job attachment report.

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What is a Satellite ?
A satellite is a specialized wireless receiver/transmitter that
repeats radio-frequencies.
It is launched by a rocket and placed in orbit around the earth.
There are hundreds of commercial satellites in operation
throughout the world.
These satellites are used for a wide range of purposes
including Internet access, television broadcasting, wide-area
network communication, weather forecasting, amateur radio
communications and the Global Positioning System.

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Various Purposes For Satellites
Satellites are used for many purposes such as :
Communications
Remote Sensing
Navigation
Atmospheric Conditions
Weather
Search and Rescue
Astronomy

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Some World Satellite Communication Providers
Telesat
MSV
Intelsat
PanAm Sat
Eutelsat
Loral Skynet
HNS-Spaceway
Inmarsat
SES Astra
Arabsat
SMART-ACeS

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What Is An Orbit?
After launch, a satellite is placed in orbit around the earth.
The earth’s gravity holds the satellite in a certain path as it
revolves around the earth.
This path is called an “orbit”.
There are several kinds of orbits. They are :
I) LEO, or Low Earth Orbit
Ii) MEO, or Medium Earth Orbit
Iii) GEO, or Geostationary Earth Orbit-Mohakhali Satellite
E/S is on this orbit.
Iv) HEO, or Highly Elliptical Orbit

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GEO, or Geostationary Earth Orbit
A GEO is 35,650 Km above our planet’s surface.
A satellite in geosynchronous orbit circles the earth in 24 hours-
the same time it takes the earth to rotate once.
These satellites are positioned over the equator and travel in
the same direction and speed as the earth and therefore
appear “fixed” with respect to a given spot on earth.
In this high orbit, GEO satellites are always able to “See” the
receiving stations below, and their signals can cover a large
area of the earth.
Three GEO satellites can cover the globe, except for the parts
at the North and South poles.
Most communication satellites
Mohakhali Standard-A Satellite E/S is on the GEO.

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How a Satellite Works
Satellites have a few basic parts. They are the :
Command and Telemetry
Power source
Pointing Control
Mission payload
Communications

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Tracking Telemetry and Control
This is the on-board computer of the satellite which controls all the
tracking, telemetry and control functions of the spacecraft.
It records every activity of the satellite, receives information from the
ground station and takes care of any general maintenance items the
satellite needs to do.
Power Supply
The power supply to satellites is provided primarily by means of the
solar arrays.
The solar arrays convert sunlight to electricity which is stored in
batteries and distributed to all the satellite’s instruments.
Batteries are required to power the satellite during eclipse when the
earth blocks the sun’s rays.
Pointing Control
The pointing control system keeps the satellite course and pointing in
the correct direction.
The system utilizes sensors to obtain pointing control.
A propulsion mechanism or momentum wheel provides the satellite
with a ways to move into the proper position when required.
Communications
The communications system is made up of a transmitter, a receiver
and several antennas to relay messages between the satellite and
earth.
Ground control also uses it to send operating instructions to the
satellite’s computer (telecommand)
This system also sends health information generated by the satellite
back to earth (telemetry)

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Uplink / Downlink
An uplink is the transmission of a signal from an earth station to a satellite
in orbit.
A downlink is characterized by the satellite receiving the uplinked signal,
amplifying it, shifting it to a lower frequency and then re-transmitting from
the satellite antenna to an earth station(s) on the ground.
C-band uplink frequencies are from 5.925GHz to 6.425 GHz and the
downlink frequencies are from 3.7GHz to 4.2GHz.
Satellite Transponder Capacity
A transponder is the part of the satellite that receives signals and
transmits signals back to Earth.
A typical Ku band satellite and C band satellite have 32 (27 MHZ wide)
transponders and 24 (36 MHZ wide) transponders respectively.
A single transponder on one of these satellites is capable of handling an
immense capacity of information which typically corresponds to the double
of is bandwidth in million bits of information per second, i.e., 72 Mbit/s
and 54 Mbit/s for C band and Ku band transponders respectively.
Today’s communication satellites are an ideal medium for transmitting and
receiving almost any kind of content, from simple data to the most
complex and bandwidth-intensive video, audio and data content.

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Satellite Frequency Bands and Antenna Size
Commonly used satellite frequency bands are L, C, and Ku.
C and Ku are the most common frequencies for fixed satellite services
such as video, data and voice.
L is the most common frequency for mobile satellite services such as
voice and data.
Ka-band will be used in the near future for video and data services.
The frequency and power output of a satellite signal determine the size
of the earth station antenna. When the frequency increases, the
wavelength decreases. As wavelength increases, larger antenna are
necessary to gather the signal.
Frequency Review : C-Band
Introduced in the 1970’s.
Occupies the 4-6 GHz frequency band.
Shared band with terrestrial microwave.
C band channels are typically 36 MHz.
Typically provides national domestic, regional or even global coverage.
Characterized by higher availability links that are less susceptible to
rain fade.
Lower cost per MHz when compared to other frequency bands.
Larger antennas required when compared to other frequency bands.

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Mohakhali Standard-A Satellite Earth Station Link
The Satellite Earth Station Link of Mohakhali Standard-A Satellite E/S
comprises of the following equipments :
1. Modem (Modulator/demodulator)
2. Combiner
3. Divider
4. Upconverter
5. Downconverter
6. HPA (High Power Amplifier)
7. LNA (Low Noise Amplifier)
8. DCME (Digital Circuit Multiplication Equipment)
9. LRE (Low Rate Encoding)
10. Antenna
TX
RX
M
O
D
E
M
COM UC HPA
DIV DC LNA
D
C
M
E
COM UC HPA
DIV DC LNA
M
O
D
E
M
TX
RX
ITX
IGW
ITX
IGW

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Modem (Modulator/demodulator)
A device that converts binary data streams, such as those from a PC, to
communicate over an analog transmission medium such as telephone lines or
on a carrier wave for wireless transmissions. The satellite modem can either
connect to the computer serial port, or to a network device via an Ethernet
connection.
Combiner
Combiner is used for 6 GHz band signal in satellite communication E/S. This
equipment requires no power supply and does not need any adjustment.
Electrical performances are as follows :
Frequency range 5850 to 6425 MHz
Insertion loss is more than 5 dB
Input/Output impedance 50 ohms
Return loss : unbalanced more than 17 dB
Isolation : more than 40 dB
Upconverter
A device that increases the frequency of the carrier, typically from
Intermediate Frequency (IF) to Radio Frequency (RF). The upconverter is
used in the transmission system or satellite communication earth station
which converts a 70 MHz or 140 MHz IF signal into a 6 GHz RF signal.
Downconverter
A device that lowers the frequency of the carrier, typically from Radio
Frequency (RF) to Intermediate Frequency (IF). It provides frequency
conversion of 4 GHz band received signal into a 70 MHz or 140 MHz IF signal
in satellite communication.

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HPA (High Power Amplifier)
A device that amplifies a specific band of frequencies by a large amount,
sufficiently large to enable the antenna to beam them up to the satellite. This
equipment has the following advantages :
High reliabilities
Solid-state IPA
Low noise figure
High gain stability
Automatic recycling
Low in rush current
All air-cooled ventilation
The frequency range of HPA is 5.850 MHz to 6,425 MHz
HPA works in two circuits polarization :
RHCP (Right Hand Circuit Polarization)
LHCP (Left Hand Circuit Polarization)
LNA (Low Noise Amplifier)
A device to amplify the received modulated carrier while minimizing noise.
The LNA subsystem which is designed for use in the satellite communication
earth station, offers ultra low noise performance over the receiving frequency
band of 3.625 GHz to 4.2 GHz. Three FET Low noise Amplifier is mounted in
a redundant configuration.

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DCME
Digital Circuit Multiplication Equipment (DCME) is a type of voice
compression equipment that is installed at either end of a long-distance link
(typically communications satellite or submarine communications cable). There
are five types of DCME used in Mohakhali Standard-A Satellite Earth Station.
They are as follows-
1. DCME DX-3000 made by Mitsubishi Corporation of Japan
2. DCME DX-7000 made by Mitsubishi Corporation of Japan
3. DCME L3 MAX Pro made by UK
4. DCME DTX-240 made by ECI Telecom
5. DCME DTX-360 made by ECI Telecom
LRE (Low bit Rate Encoding)
Low bit Rate Encoding. One LRE is used in Mohakhali Satellite E/S and it is
made by Tellabs Ltd of Ireland.
Antenna
A device for transmitting and receiving radio waves, usually designed to focus
the waves to or from one direction. The antenna is often referred to as a dish.
The antenna also contains the feedhorn. The feedhorn is piece of antenna
hardware, located at the focal point of the parabolic reflector, that radiates RF
energy toward the antenna reflector and collects (received) RF energy from
the antenna reflector.

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Power System of Mohakhali Satellite E/S
Generally power supply comes from PDB. If PDB fails, power
supply comes from UPS battery instantly and uninterruptly.
After a few seconds generator will start automatically and takes
load until PDB power supply comes.
My Job Responsibilities
Run international circuits smoothly
Observe & operate communication equipments with frequency
level analysis
Recover communication hindrance through manually and with
application software
Maintain international incoming and outgoing calls
Conclusion
Every organization needs well-adjusted, trained and experienced
people to perform its activities. In this regard, employee training is a
must because it is learning experience which seeks a relatively
permanent change in employees. The knowledge and practical
experience achieved in the field training provided by our concerned
officers has greatly benefited us to enhance our technical job skills
and overall improve our job performance.

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25 July, 2011
To
Ms. Mst. Mallika Akar Khanom
Superintendent (Exam & Program),
Telecom Training Center, BTCL, Tejgaon, Dhaka.
Subject : Submission of Job Attachment Report.
Dear Madam,
Here is the Job Attachment Report on “Mohakhali Standard-A Satellite E/S”
where I have achieved my experience at my job area Mohakhali Satellite Earth
Station, Karail, Banani, Dhaka. The duration of Job attachment Programme was
one year. I have worked in the Earth Station as a Telecom Mechanics (TCM). I
have gathered practical knowledge in “Satellite Communication System” I have
found it interesting and acquired valuable practical knowledge while working for
this report.
I am very much grateful to you for your valuable advice, suggestion and co-
operation in preparing this report. I sincerely believe that this report would be
interesting, informative and acceptable to you.
Sincerely yours,
(Mohammad Mijanur Rahman)
Roll No.-1, Batch- TCM (Ext.)-09-10
Telecom Training Center, BTCL, Tejgaon, Dhaka.