If you’re reading this page,
know that you are in good company. All satellite installers
were new to satellite technology at some point in
time. This program is aimed at giving you a foundation
of satellite installation technology so that you may be confident in your installation at any location. For those that are somewhat knowledgeable in satellite communication technology, this online training program is likely to help to fill in some gaps.
This is a broad question, but in general terms, Satellite
communication, (sometimes referred to as satellite Internet) is the ability to transmit and receive data
from a relatively small satellite dish on Earth
and communicate with an orbiting Geostationary satellite
22,300 miles above Earth's Equator. In turn, the
orbiting satellite transmits (and receives) its information
to a single location called the Network Operations Center
or NOC (pronounced "knock"). The NOC itself
is connected to the Internet (or private network), so
all communication made to the Internet must flow
through the NOC.
This is a simple diagram on the left shows how data moves through the a satellite network.
Data communication via satellite is not much different
than someone using a land based data provider, at least
from the end-users standpoint. The key to remember is that
once the satellite system is configured by the installer,
the service acts nearly identically as any other data service
and may be configured as such.
There is a location in space where you can place a satellite in orbit so that
from the ground, the satellite appears stationary. What is happening is that
the satellite is actually orbiting the Earth at the same speed the Earth is
rotating. The satellite makes a complete orbit around the Earth in 24 hours,
or exactly one day. Geostationary satellites are only located at 22,300 miles
directly above the Earth's equator and nowhere else.
All Geostationary satellites have a name like "G-18" or "AMC-4". These satellites will also have a longitudinal position - 117w or 101w (the "w" stands for "west" or western hemisphere). All satellite longitudes will be either East or West, though all installations in the western hemisphere will use Western Longitude satellites.. You can refer to a satellite either by its longitude or by its name.
Longitudinal lines travel from pole to pole vertically along the Earth. There are
360 degrees of longitude readings for Earth (360 degrees
is a full circle). If one knows the longitude of
a satellite, one knows where the satellite is located
in the sky because all Geostationary satellites are always
located above the equator (or zero latitude).
AMC-4 has a position
of 101 degrees Longitude. If you were to follow
Longitude 101 north from the Equator, you would run through
the middle of Texas, up through the middle of North Dakota.
It takes time for a satellite signal to be sent from your
dish to the orbiting satellite back down to Earth… The
speed of light is 186,000 miles per second and the orbiting
satellite is 22,300 miles above earth. Calculated out, satellite
latency is roughly ½ of a second, which is not a lot
of time, but a few applications such as VPN (Virtual Private
Network) don’t like this time delay. It is important
to know if Satellite Latency will affect the way you will
use the Internet.
A common misconception is that latency has an effect on
transfer rate. This is not true. A one Megabyte file will
transfer just as quick over a 1000Kbps satellite connection
as it does over a 1000Kbps terrestrial connection. It just
takes the satellite connection less than a second for the
file to begin transferring.
You will hear this term often in the satellite Internet world.
It refers to a trick that is used by the satellite industry
to effectively double the transmission potential of satellites
by transmitting on Vertical and Horizontal planes or "Polarities".
Using differing polarities allows service providers to re-use the same frequency by simply
transmitting a vertical wave or a horizontal wave.
To capture the signal is the job of the "Wave-Guide",
which is a portion of the satellite dish electronics. The
wave guide has vertical and horizontal openings that create
a "polarity" filter for the incoming (or transmitting)
signal. Below, the Wave Guide can be seen among the radio
assembly of the satellite dish.
Note that the physical rectangular dimensions of the waveguides
openings determine the polarity of the incoming or outgoing
signal. Note that a vertical rectangular channel of the Receive
Feed is receiving HORIZONTAL waves (which is counter intuitive).
This is the same for the transmit feed who's horizontal rectangular
opening will transmit VERTICAL waves.
As always, refer to your installation documentation for the correct polarization of the equipment. For this demonstration and this course, we will be working with AMC4 - 101W which receives Horizontal and transmits Vertical.
Knowing that a satellite in orbit transmits on a vertical
or horizontal polarity, then it should come as no surprise
that you will need to rotate (or SKEW) the radio assembly
so that you be aligning the dish electronics to be perfectly
in line with the orbiting satellite signals. We will get
in more detail on this process in a different chapter dealing
with the actual dish installation.
For now, just take a look at this picture and understand
that rotating/skewing the radio assembly is the process of
aligning the dish with the orbiting satellite horizontal
and vertical polarities. This process is known as "Cross
Rotating or "Skewing" the radio
assembly to align to the orbiting satellite
In order for a 2-way dish to communicate properly with the satellite in orbit,
the signal that transmits from the dish must be precisely timed to be received
by the Satellite. If the transmission is received a fraction of a second late
or early, communication will not exist. A transmission from Texas arrives at
the satellite faster than a dish located in Canada because Texas is physically
closer to the satellite. This process of timing a satellite is sometimes called "ranging" because
you are defining the range between the satellite dish and the satellite. Ranging
needs to be extremely precise by using a handheld GPS device to give you your
current installation location.
The footprint of a satellite shows the location that a satellite
dish may be located to communicate with the satellite. Below
is the footprint for AMC-4 for North America
- Effective Isotropic Radiated Power In the above
footprint, the numbers in red represent the EIRP regions
on the planet. The number itself is a representation of Decibels
"dBW" or power level of the EIRP (in reference to one watt.
The higher the dBW, the greater the
signal strength. If you
low EIRP dBW level,
may have to use a larger satellite dish in order to receive
Below is an example of a footprint that shows the minimum size of satellite
dish required for connectivity in certain regions in North America.
Satellite communications are radio transmission in the KU
Band of the electromagnetic spectrum. The KU Band is the
same band that police officers use for their radar detectors.
KU Band satellite dishes transmit between a frequency of
14000 to 14500 MHz.
They receive a frequency range between 11700 to 12750 MHz.
Other common Satellite bands are C-Band and KA-Band.
Satellites use TRANSPONDERS to communicate with the Earth.
picks up on a small slice of the KU Frequency Band. The Satellite
transponders and "Transmit" transponders. When you
make a request to the
Satellite for a web page, you transmit to a receive transponder
on the Satellite.
The Satellite then sends it down to Earth with a "Transmit" transponder.
the satellite can be thought of as a giant "repeater" in
Below is a picture of the 24 transponders (or frequencies)
of AMC 4 for the uplink
(up to the satellite) and downlink (down from the satellite).
Note that the frequencies of AMC 4 are somewhat rectangular
looking, and in the center of the rectangle is the "center
frequency" of that transponder. This term Center Frequency
is used during your installation.
On a spectrum analyzer, the frequencies look like this:
A spectrum analyzer is helpful in fine tuning
the aiming of your satellite dish. In this program, we will
show you how to use the Birdog satellite pointing utility
which is easier to operate than a spectrum analyzer. We will
cover that in the hardware installation section of this program.