GVF VSAT Install and Maint Handbook Level 3 Rev1 31 OB
GVF VSAT Install and Maint Handbook Level 3 Rev1 31 OB
GVF VSAT Install and Maint Handbook Level 3 Rev1 31 OB
Onno Beemsterboer
Ralph Brooker
The Global VSAT Forum (GVF) is a not for profit organization comprised of a large number of satellite
communications companies from over 60 countries in every major region of the world. The GVFs mission is to act in
an independent manner for the general promotion of the global VSAT Industry, whether this be technology or service
based. The Global VSAT Forum represents the best interests of its membership at relevant industry symposia,
regulatory and legal consultations and forms a single point of contact for any suppliers to the industry or any users of
VSAT equipment or services. The Forum's actions are always consistent with the promotion and growth of the VSAT
Industry and its membership.
Dear Reader,
Everyone knows that modern communications satellites are at the heart of the high quality telecommunications
services satellite service provides to our myriad customers around the world. However we sometimes take for
granted just how remarkable these satellites and their associated ground systems have become. Weighing about the
same as a full size American car, when these satellites roll of the assembly line their fuel tanks will be filled and then
they will be subjected to the full force and fury of a controlled explosion known as a launch vehicle. With several
additional pushes from an internal rocket, after two weeks they will finally arrive at the proper orbital slot 22,300 miles
above the earth. For the next thirteen to fifteen years, in spite of the continuous push from the solar wind and the
constant pull of gravitational forces, the satellite must be kept in exactly the same position - again using internal
rockets under ground control - so that the customers antennas will not have to search to find it. After the antennas
and solar panels are unfolded and a short period of testing is completed, the satellites will be expected to run twenty
four hours a day, seven days a week for thirteen to fifteen years with no stops at the dealer for repairs or even routine
maintenance. They will also be expected to provide continuous communications services between all points on the
earth within the antenna footprints carrying huge volumes of video, voice and data for your or your companys
customers.
One of the goals of this training manual is to make the development, launch and operation of these modern
miracles and the installation of ground segment as earth stations look easy to you as a VSAT Technician and
ultimately, to your worldwide customers.
Because satellite technology is a rapidly evolving area of technology it cannot be over-emphasized that training
should be a continual activity. It is necessary that both the executive and technical staff keep up-to-date with
technological developments in this field. As a minimum, VSAT technicians should have good knowledge of RF
transmission, digital technology and some knowledge of mechanical systems. Managers need to understand the
importance of continuing education for personnel to enhance knowledge, improve skills and keep up with new
technology.
This Training Manual provides the reader with an overview of satellite technology and VSAT technology in particular.
In addition, it addresses issues typical to all VSAT installations. It should be noted that the issue of human health and
safety from electromagnetic radiation is not included in this manual, as compliance with national and regional
standards and limits in this area is insured through each national licensing process.
Please take your time to read through the manuals and make notes where required. If necessary, insert comments,
remarks or questions.
The Manual is far from perfect but efforts will be made to keep it updated. In addition this paper is written by a nonnative English speaker what occasionally may result in funny grammar.
At any time never hesitate to contact me for remarks, suggestions or critics.
Amsterdam, The Netherlands.
August 2003
Onno Beemsterboer
GVF Education & Training Working Group
Email: obeemsterboer@tiscali.nl
Email: obeemsterboer@gvf.org
Phone: +31 186 618799 / +31 651 241470
Table of Contents
VSAT Installation & Maintenance Training
History Edition
Version
Date
Author
Notes
Draft 0.0
Rev 1.0
Rev 1.1
Rev 1.2
Rev 1.3
30 April 2003
22 July 2003
10 September 2003
18 November 2003
14 December 2003
Onno Beemsterboer
Onno Beemsterboer
Onno Beemsterboer
Onno Beemsterboer
Onno Beemsterboer
Rev 1.31
3 February 2006
Onno Beemsterboer
Initial set-up
Implementation of suggestions
Implementation of suggestions
Adding copyright clause
Update introduction; update charts on page 122
and 125
Level split and update
Part 2 Level 3
VSAT Technology Basics
6
1.2, 1.5, 1.8, 2.4 or 3.7 meter antenna, occasionally with de-ice incorporated in one or more antenna panels,
and preferable a non-penetrating antenna mount with sufficient ballast;
Satellite transceiver unit including radio and LNB/LNC;
Satellite modem unit;
Optional: Multiplexer unit;
Optional: Router unit;
Optional: Monitor and Control (M&C) unit;
Optional: Telephone modem unit to support the M&C unit;
IF (Inter Facility) and M&C (Monitor and Control) cables and connectors;
Modular uninterrupted power system (UPS) unit; and
Equipment rack with internal cables and wiring.
2. Site Survey
2.1. The purpose of a site survey:
To gather site specific information necessary to design and implement the customer contract requirements
To ensure that the chosen installation site has a clear view to the desired satellite
To select the best placement for the antenna
To determine the type of mount needed
To document the location of the indoor equipment
To determine and document the path and length of the cable run
To discover and document any special problems that may affect the installation such as landlord approval or
contractor issues
To identify or confirm interface requirements
To obtain information needed to procure permits and licenses
Elevation: The vertical angle measured from the horizon up to a targeted satellite. When the beam axis is
parallel to the ground, the elevation is zero. A 90o-elevation rotation points the beam to the zenith.
Azimuth: Angle between antenna beam and meridian plane (measured in horizontal plane). The zero reference
for measuring true azimuth is north, east is 90o, south is 180o and west 270o.
er
et
om
90
om
in
cl
In
90
in
cl
In
Step1: Know the orbital position of the satellite and the geographic location of the antenna. As an example
Astra-1A is located in the 19.1 East slot. Be advised that this is not your compass readout unless your
antenna is on the equator.
Step2: Calculate the azimuth and elevation for the specific satellite for your specific location
Step3: Read the compass at ground level. Stay away from motors and large steel constructions.
Step4: To find the true azimuth you first must subtract or add the variation to your compass reading.
Step5: Identify a landmark in the assigned azimuth pointing direction and refer to the landmark when
pointing the antenna.
Offset angle
e
et
r
Elevation = 90 - X + Offset
Elevation = 90 - X
2.2.2. Obstructions
It may happen that there is an obstruction between the antenna and the satellite. For each meter from the center
post, the rise (line B on the drawing below) can be calculated from the tangent of the elevation angle. To find out if
the height of this obstruction will cause problems for your installation first measure/calculate the antenna elevation.
Second measure the distance C. C is the distance between antenna center post and imaginary line perpendicular
from the highest point of the obstruction to the ground.
Elevation
(degrees)
5
10
15
20
Rise B (cm)
for each meter C
8.74
17.63
26.79
36.39
Example: An obstruction of 4 meters (this could be a tree?) is right in front of the antenna. The elevation is 10
degrees. The distance C between antenna and obstruction is only 25 meters. Is there any problem? No, because the
rise B for each meter C is tg (10) = 17.63 cm. The total rise over 25 meters is 25 x 17.63 = 438.73 cm = 4.38 meters.
Conclusion: the tree may grow another 38 cm before you face serious problems.
10
A compass
An inclinometer
A measuring tape
A marker
Standard Site Survey Form (see Appendix for example)
(Digital) camera
11
12
The standard installation includes a standard site survey at the location, local license application(s) (if necessary),
IDU/IFL/ODU installation, Customer instruction and hand-over and the return of Service Acceptance Test.
A 1m - 2.4m antenna installation requires maximum one qualified technician and one assistant on site.
A 3.8m antenna installation requires one qualified technician and two assistants.
Installation of a satellite antenna with maximum 3.8m aperture diameter including mount and ballast.
Antenna size is specified by the service provider or customer and can be with or without de-icing. Typical
mount construction is non-penetrating; Typical de-icing is a de-ice system integrated in one or more antenna
panels; and
Installation of digital low noise block converter (LNB or LNC) and radio transceiver; Installation of power
cable, M&C cable and coaxial cable including connectors. Peak and pole of antenna and level check in
cooperation with satellite operations center. Programming and testing of digital base band equipment
including a 8h BER test; and the installation of the monitor and control (M&C) device.
Outdoor Unit
Indoor Unit
De-Ice
IFL
Feed
Equipment
Rack
RX
TX
Twisted Pair
M&C
M&C
SLP
Power Cable
Building
Ground
13
Power
RX
Twin Coax
Radio
Unit
M&C
UPS Power
Antenna
Mount
Building
Ground
Installation of IFL
Installation of IDU
Installation of ODU
Cross-pol and line up & level setting*)
*) In order to maintain strict control over the transponders, many satellite companies have published the Satellite
Access Procedures. These procedures outline the method for a customer to arrange for a service contract and
receive frequency assignments. They also provide instructions for a customer to receive authorization to transmit to
the satellite and the step-by-step process for verifying performance of their up-link equipment. Most importantly, the
Satellite Access Procedures grant the Satellite Operating Center the authority to deny access or terminate the
transmission of any customer that is violating the terms of the agreement or is operating in a way that causes
interference or threatens the health of the satellite.
14
Samples of all the documents listed below can be found in the Appendix. If you believe something is missing
immediately contact the responsible Program Manager or Network Engineer.
As a minimum you should have for every node in the network:
3.2.3. Check all necessary tools and test equipment is available on site.
To meet common standards proper tools, test and measurement equipment required to perform installation and
repair of VSAT systems is absolutely indispensable. For those Installers who want to update their inventory of test
equipment it is recommend a visit to the following websites:
Companies selling (used) test equipment at often reasonable prices
Company
Telogy Networks
Electrolab
The Test Equipment Depot
Planet Test
Instrumex
T.O.P. Electronik
Metric
15
Internet address
http://www.telogy.com/
http://www.electrolab.com/menu.htm
http://www.testequipmentdepot.com/
http://www.planettest.com/
http://www.instrumex.de/
http://www.topelektronik.de/
http://www.metricsales.com/
Language
English
English
English
English
German
German
English
Additional materials
The following materials can be very useful on site:
16
A Basic Toolkit
The antenna is a passive element and its size is directly proportional to the to be transmitted amount of bandwidth
(which is related to power). The main differences between the 1.2m, 1.8m, 2.4m and the 3.7m antenna can be found
in the antenna gain (which is determined to a great extent by its diameter) and antenna efficiency.
1
2
3
4
Feed construction
Radio unit or transceiver
IFL cables
Non penetrating mount
5
3
2
4
17
Note: An offset reflector contains a X elevation offset look angle. Therefore, when the reflector aperture is
perpendicular to the ground, the antenna is actually looking X in elevation. X is antenna specific and can be found
back in the manufactures manual.
The heart of every rack is the satellite modem what includes the interface to the customer's equipment, the data
encoder/decoder (codec) and a modulator/demodulator. In fact the satellite modem produces the signal for the uplink,
and demodulates the received downlink signal. The modem(s) is (are) connected to the Outdoor Unit via the IFL
cables. The indoor unit is a rack containing as minimum configuration, all the necessary channel equipment, the
monitor & control (M & C) unit and a PSTN modem are optional. Depending on the application, an UPS unit,
multiplexer, and router(s) can be installed in addition.
A Monitor and Control (M&C) unit collects status information from the VSAT site including the transceiver and reports to the
Network Operations Center via a PSTN modem, either automatically or in response to a query. It also gives the NOC the ability
to dial into the site for reading (and changing) the equipment settings without dispatching a technician.
To improve the MTBF (mean time between failure) keep the power always switched on. Never switch off the electrical
equipment for the weekend!
18
E
N
C
O
D
E
R
TX-IF-Out
-3.7
dB
Attenuator
From Indoor
Unit
D
E
C
O
D
E
R
IFMODEM
RX-IF-Out
Attenuator
-3.7
dB
From Outdoor
Unit
Terminator
Satellite Modem
Divider
3.0 dB
4.8 dB
6.0 dB
7.8 dB
9.0 dB
IN1 / UIT1
-3 dB
IN / UIT
-3 dB
Isolation
Between
1 and 2:
-30 dB
IN2 / UIT2
A standard two-way combiner / divider. The loss between in out is -3.7 dB (this is including the
connector losses). The isolation between in1/out1 and in2/out2 is about 30 dB but depends very
much on the correct impedance termination. If one of the in/outputs is left unterminated the isolation
can drop to 10 dB.
19
Be aware, a splitter is directive and cannot be connected in any way you like. Commercial splitters have an in- and
output impedance of 50 or 75 and the pass band is flat from 5 MHz to 1 GHz or higher. Many companies uses
Mini-Circuits 75 types and are flat to 500 MHz. Unused out- or inputs always have to be terminated with the correct
characteristic impedance.
Depending on the quality and the length of the IFL cable run, the cable has a certain attenuation. For example the Olympic Twin
coaxial cable has for 70 MHz an attenuation of 6dB/100m. Since the minimum output level of the satellite modem is -25 dBm this
attenuation is often not enough to avoid overdriving the radio when connecting the modem output via the IFL cable to the radio.
For this reason the use of fixed attenuators is absolutely necessary.
Attenuators in the RX path are often required for not overdriving the input stage of the demodulator.
20
All equipment located within a common rack is bonded together and grounded to a proper ground;
Verify the IFL is connected to the indoor unit, and the indoor unit is connected to a pre-tested AC receptacle. A
pre-tested AC receptacle is one that has a good ground and no polarity reversals. This may be checked with a
standard ac receptacle checker;
The IDU is secured to a stable flat surface or in an equipment rack with adequate air circulation;
The IDU is located within a sheltered environment, away from sources of water, extreme cold and heat, vibration,
dust or excessive electromagnetic interference (EMI);
The PSTN modem is connected to a working telephone line. The providers Network Operations Center (NOC) is
informed about the telephone number and should have the possibility to dial up the device;
4. Data interfaces
Data interfaces (Physical Layer or Layer1 from OSI Reference Model) are used to connect user devices into the
communications circuit. Most interfaces describe four attributes of the interface:
1. Electrical Electrical describes the voltage (or current) levels and the timing of the electrical changes to represent a
0 or 1
2. Functional - Functional describes the functions to be performed by the interface. As there are control, timing, data and
ground;
DTE stands for Data Terminal Equipment and is a typical end-user device, such as a terminal or computer.
DCE stands for Data Circuit-terminating Equipment. DCE provides the DTE a connection into the communications
circuit. A telephone modem is an example of a DCE.
X.21 is a ITU recommendation for operation of digital circuits. The X.21 interface operates over eight interchange
circuits(i.e. signal ground, DTE common return, transmit, receive, control, indication, signal element timing and byte
timing) their functions is defined in recommendation X.24 and their electrical characteristics in recommendation X.27.
X.21-bis is an ITU recommendation that defines the analogue interface to allow access to the digital circuit switched
network using an analogue circuit. X.21-bis provides procedures for sending and receiving addressing information that
enable a DTE to establish switched circuits with other DTEs, which have access to the digital network.
X.25 - The first international standard packet switching network developed in the early 1970s and published in 1976
by the CCITT (now ITU). X.25 was designed to become a worldwide public data network similar to the global
telephone system for voice, but it never came to pass due to incompatibilities and the lack of interest within the U.S. It
has been used primarily outside the U.S. for low speed applications (up to 56 Kbps) such as credit card verifications
and automatic teller machine (ATM) and other financial transactions.
21
X.25 describes the interface between DTE and DCE for terminals operating in the packet mode on public data
networks and provides a connection-oriented technology for transmission over highly error-prone facilities, which
were more common when it was first introduced. Error checking is performed at each node, which can slow overall
throughput and renders X.25 incapable of handling real time voice and video.
RS-232 (equal to V.28) RS-232 describes the interface between DTE and DCE employing serial binary data
interchange. RS-232 is a standard for serial transmission between computers and peripheral devices (modem,
mouse, etc.). Using a 25-pin DB-25 or 9-pin DB-9 connector, its normal cable limitation of 50 feet can be extended to
several hundred feet with high-quality cable. RS-232 defines the purpose and signal timing for each of the 25 lines;
however, many applications use less than a dozen. RS-232 conveys data across the interface by changing voltage
levels.
RS-422 - A standard for serial interfaces that extend distances and speeds beyond RS-232. RS-422 is a balanced
system requiring more wire pairs than its RS-423 counterpart and is intended for use in multipoint lines. Both use
either a 37-pin connector defined by RS-449 or a 25-pin connector defined by RS-530. RS-422 caters for a line
impedance of as low as 50 ohm and supports data rates of up to 10 Mbps.
RS-423 - As RS-422 however RS-423 describes the electrical characteristics of unbalanced voltage digital interface
circuits. RS423 supports a maximum data rate of 100kbps.
RS-449 RS-449 is a further enhancement of RS-422 and RS-423 and defines a 37-pin connector for RS-422 and
RS-423 circuits. RS-449 caters for data rates up to 2 Mbps.
RS-530 - RS-530 defines a 25-pin connector for RS-422 and RS-423 circuits. It allows for higher speed transmission
up to 2Mbps over the same DB-25 connector used in RS-232, but is not compatible with it. See RS-422.
G.70X / G.73X
TBW
22
Prior to installation (and preferable during the site survey) plan the route that the IFL cable will follow. Plan
the route to minimize the cable length between the IDU and ODU. Keep in mind that approximately 150 cm
(five feet) at both ends should be added for drip loops and service loops.
Ensure that a strain relief is added to both cable connections.
Use the correct crimp tool for crimping connectors to the cables.
Ensure that all the external connectors are sealed and waterproofed.
With the coaxial cables disconnected from the RF Unit, measure the AC voltage between the shield of the
coaxial cable and the proposed ground wire. If no AC voltage is present, change the meter to read
resistance and measure the resistance from the IFL shield (still not connected to RF Unit) to the ground
wire. The resistance should be 25 or less.
In addition, a twisted pair cable connects the transceiver monitor and control port to the M&C unit indoors. Other
cables include a telephone line for the telephone outlet in the SLP box, and a power cable between UPS and RFU.
Be advised that equipment ground wires should be separated from all other conductors, and should not be run
through metal conduit unless the conduit and ground wires are bonded at both ends.
The life of an IFL cable depends on many factors. Some of those factors are ultra-violet exposure, migration, high
humidity, age, corrosion, power/heat, and voltage. In summation, in general cable can perform to its maximum
designed efficiency an average of seven years to ten years, provided the connectors are appropriately terminated and
the cable is installed correctly.
23
Coaxial Cable Loss in dB per 100ft. Horizontal axis represents frequency, vertical axis represents attenuation.
24
5.3. RF connectors
With all coaxial RF connectors, be sure to consider the dimensions of the cable youll be using. Coaxial cables come
in a variety of diameters that are a function of their transmission properties, series ratting, and number of shields
and jackets.
5.3.2. F connectors
The type of coax connector you are most familiar with is probably the one you have in your home for use with video
equipment. F connectors are standard 75 and require a crimp tool for proper mounting to the cable. A cheaper Ftype connector available at some retail outlets attaches to the cable by screwing the outer ferrule onto the jacket
instead of crimping it in place. These are very unreliable and pull of easily. Their use in residences is not
recommended, and they should never be used in commercial applications.
5.3.3. N connectors
The N connector was invented by and named for Paul Neill of Bell Labs. It was the first connector capable of true
microwave performance. N connectors have threaded coupling interfaces and are 50 in impedance. There are also
75 versions available, but they will not mate with the more common 50 version. N connectors operate up to 11
GHz in the common 50 impedance design. Although less common, there are also precision versions of the N
connector available which operate up to 18 GHz. Applications for the N connector include Local Area Networks
(LANs); test equipment; broadcast, satellite and military communication equipment.
BNC Type
F Type
N Type
Only use connectors that fit your cable and always test your cables before final installation. Loose connectors
contribute to signal ingress and egress, cause problems with return path services and can affect link availability.
25
26
Power Consumption
100 - 160 W
125 - 174 W
200 - 275 W
300 - 421 W
Type of Equipment
10 W C band Radio
20 W C band Radio
Satellite Modem
Nuera Multiplexer
Power Consumption
150 W (Anacom)
225 W (Anacom)
35 W
526 W
The above information can generally be obtained from the satellite operator, or from a good satellite database such
as e.g. http://www.satnews.com on the Internet. Other sources of this data include printed media, such as the Global
Satellite Directory from Phillips Publishing.
You will also need the following information:
27
Desired link availability as agreed with your customer. Link availability is normally taken as 99.5% of an
"average year" for single VSAT systems, and 99.9% or greater for redundant systems.
Transmission Losses or Free Space Losses. This is the attenuation that a signal undergoes as it travels over
the path between the earth station and the satellite. Losses are due mainly to the spreading out of the signal on
its long journey, and are dependent on the distance (GEO, MEO or LEO) and the signal frequency.
At 12 GHz the path loss equals 205.11 dB when the receiving earth station is located on the equator directly
below a GEO-satellite. In other locations the path loss is slightly more. Also different path losses apply for other
frequencies as C band and Ka band.
Atmospheric absorption or Rain Fade. The main components, which are difficult to predict, are atmospheric
absorption and attenuation due to precipitation. Atmospheric absorption by water vapor and oxygen is basically a
clear sky effect (happens whether raining or not) and depends mainly on the absolute humidity or vapor density
measured in grams per cubic meter. However, this is a relatively minor contributor below about 7.5GHz.
The effects of precipitation become significant above about 8GHz. Rain, or to a lesser extent snow, fog, or cloud will
attenuate and scatter microwave signals. The magnitude depending more on the size of the water droplets (in cubic
wavelengths) rather than the precipitation rate itself. Heavier rain tends to comprise larger droplets so the two are normally
related. Thunderstorms are perhaps the main offender in this respect. In addition, rain has a noise temperature similar to
that of the earth (260K average) which increases the sky noise temperature over the clear sky value. Based on the longterm statistics of rainfall rates for a particular area a Downlink Degradation (DND) figure corresponding to specified signal
availability may be calculated. The DND figure is the total degradation of the signal due to precipitation expressed in dB
and, for a given signal availability, consists of the sum of the attenuation due to precipitation and the system noise increase
translated to an equivalent dB loss. There is also a small contribution due to the increase in atmospheric gaseous
absorption during rain.
Rain Fade is the major component of the link margin set aside for Ku band and Ka band.
Scintillations. Another clear sky effect is the loss due to tropospheric scintillations. Turbulence caused by wind
in the atmosphere cause short duration fluctuations in the refractive index. These translate to small amplitude
fluctuations in the received signal that can be significant particularly at low elevations.
Fortunately in this age of computers and spreadsheet programs, the link budget does not have to be all that difficult to compute.
Several companies now market quite sophisticated link budget calculation programs that contain large databases of information
regarding satellite performance parameters, ground station antenna performance data, and other information vital to calculation.
With one of these programs, all the user must do is fill in the blanks regarding earth station location, planned satellite(s) to use,
required link availability, and the program generates a very good estimation of link performance.
In Ku band networks, it is a good rule of thumb to allow 7 or 8 dB of margin above threshold at the receive site with
clear sky conditions. This will generally provide link availability in excess of 99.5%. C band networks require much
less margin, typically about 3 dB, for the same performance expectation, since there is less atmospheric attenuation
with the C band.
Most satellite operators limit satellite received EIRP to a specific maximum level of 6dBW/4kHz, or about minus 140 dBW per
square meter on the ground. If spectral density exceeds these limits, you should use better LNB/Cs or larger receive antennas
to lower the power requirements. You can also spread the signal over greater bandwidth; either by changing FEC rates,
changing modulation formats from QPSK to BPSK, or by using some form of additional signal spreading.
28
Network:
Alcatel
Information Rate:
Modulation Type:
Code Rate:
128
QPSK
Link Availability:
99.62
3/4
Modem Make:
Model:
Step Size:
Min. Allocated BW:
Paradise
P300
2.5
25
kHz
kHz
85.3
102.4
119.5
120.0
kHz
kHz
kHz
kHz
kbps
Sequential
Symbol BW:
Noise BW:
Absolute Min. Alloc. BW:
Actual Min. Alloc. BW:
=
=
=
1.20
1.40
1.41
x SBW
x SBW
x SBW
-6.2
0.5
-6.7
-20.8
28.4
42.5
Clear
Sky
Probability of Rain Loss:
Uplink
Downlink
Dublin
Dublin
Ireland
53.3
6.25
F
1.6
50.7
227.2
29.0
38770
13.1
190.9
28.5
38809
5.6
2.4
2.4
110
0.2
48.2
0.65
32
0.24 W
0.21 W
LINK CALCULATION
RFT INFORMATION
Lipljan
Lipljan, Kosovo
Yugoslavia
42.5
-21.10
K
dBW
dB
dBW
dBW/4kHz
dBW/4kHz
dBW
Rain on
U/L
0.35
Rain on
D/L
0.03 %
Uplink:
Site Code:
City:
Country:
Latitude:
Longitude:
CCIR Rain Zone:
Satellite G/T & Saturated EIRP:
Geographic Advantage:
Azimuth:
Elevation:
Slant Range:
A(0.01%):
Antenna Diameter:
HPA & LNA:
Waveguide Loss:
Antenna Gain:
Antenna Efficiency:
Antenna Noise Temp. @ 20 elev. angle:
0.5
49.1
0.65
N
W
SATELLITE INFORMATION
Satellite: Orion-F2
Xpdr Number:
11
Longitude:
15
Actual BW:
54
Beam Coverage:
Beam Type:
Center Frequency:
Polarity:
Total Operating Point:
G/T & EIRP Reference Contours:
Xpdr Constant at Gain Setting of 0 dB:
Gain (Pad) Setting:
Effective Xpdr Constant:
W
MHz
Uplink
E
14.157
V
5.0
Downlink
E
BB
12.657
H
3.2
-96.7
-10.0
-86.7
GHz
dB
dB/K & dBW
dBW/m2K
dB
dBW/m2K
Limited by
29
10
kHz from
54
Power:
BW:
0.1995%
0.2222%
which is
which is
30.2
120.0
dB COPBO ref. to
kHz referenced to
3.2
54.0
dB TOPBO
MHz useable BW
Equivalent:
Power & BW:
0.2222%
which is
29.7
120.0
dB COPBO ref. to
kHz referenced to
3.2
54.0
dB TOPBO
MHz useable BW
A
B
42.5
162.8
C
D=A-B-C
E
F=E-D
G
H
I
J=F+G+H-I
K
L=J-K
M
N
O
P
Q
R
S=Q-R
T
U
V
W=S-T-U-V
X
Y
I
Z=W+X+Y-I
K
A'=Z-K
B'
C'
D'
E'
F'
I'
J'
K'
K
L'
M'
N'=L'-M'
O'
P'
Q'=N'-O'-P'
-120.3
-88.3
32.0
-44.5
1.6
-228.6
65.4
50.1
15.3
28.2
25.2
23.5
14.7
50.7
30.2
20.5
162.8
0.5
-142.8
-43.5
26.1
-228.6
68.4
50.1
18.3
16.4
27.2
23.7
15.4
13.6
13.6
14.8
11.1
50.1
61.2
51.1
10.1
2.7
0.5
6.9
2.7
-123.0
34.7
62.7
12.6
25.5
22.5
20.7
12.0
32.9
17.8
-145.5
65.7
15.6
13.7
24.5
21.0
12.7
10.9
10.8
12.0
8.4
58.5
7.4
0.0
dBW
dBm2
dB
dBW/m2
dBW/m2
dB
dBm2
dB/K
dBHz
dBHz
dB
dB
dB
dB
dB
dBW
dB
dBW
dBm2
3.6 dB
dB
-146.4 dBW/m2
dBm2
23.1 dB/K
61.8 dBHz
dBHz
11.7 dB
dB
dB
dB
dB
10.1 dB
10.1 dB
dB
8.8 dB
dBHz
58.9 dBHz
dBHz
7.9 dB
0.5 dB
dB
dB
8. Test Equipment
8.1. Oscilloscope
The standard method for observing electric signals is to use an oscilloscope. The horizontal axis of a (CRT)
oscilloscope increases by the unit of time; oscilloscopes are sometimes referred to as time-domain instruments.
Observation in time domain is useful to obtain signal timings (e.g. clocking) and phases.
Frequency (accuracy)
Absolute Power Levels
C+N/N
Bandwidth
Interfering Signals and Spurious Noise
Antenna Pointing
Modulation Check
30
Resolution: The IF filters separate the frequency components of the signals; this capability is called
resolution
Resolution Bandwidth (RBW): Spectrum analyzer specifications indicate a 3dB bandwidth for the available
analyzer filters (this is known as resolution bandwidth). The resolution bandwidth indicates how close two
equal carriers can be and still are resolved.
Video filters: The spectrum signal at the output of the IF filter is detected for final conditioning in the post
detection gain and signal processing (known as video filters) which smoothes (or averages) the signal for
final presentation. The narrower the video filter bandwidth, the more sweep time is required. If the signal is
swept too quickly, there will be a loss of displayed amplitude due to the time that the video filter takes to
charge and discharge.
BER =
A performance guarantee of BER=1E-6 for 99.5% availability means that for all year except 44 hours (of heavy rain,
snow, sun outage, interference, etc.) the link will perform at BERs much better than the threshold. During the
remaining 0.5% of the time there are more errors received than usual, resulting in more re-transmissions or a noisy
signal.
To measure the error rate accurately, a sequence of bits simulating the real data is transmitted at a rate equal to the
transmission rate. This pattern is called the Pseudo Random Bit Sequence (PRBS). The PRBS is compared with the
one generated at the receiver and the ratio of detected mismatched bits to the total number of bits is calculated as the
bit error ratio.
31
The length of the PRBS test pattern is selected according to the transmission rate of the system being tested:
Info. Rate [bit/s]
64k
192k
384k
512k
1024k
1544k
2048k
6312k
8448k
32064k
34368k
44736k
PRPL [bits]
2047 (211-1)
2047 (211-1)
2047 (211-1)
2047 (211-1)
2047 (211-1)
215-1
215-1
215-1
215-1
215-1
215-1
215-1
As an example if the data rate is 64 kbps than the time needed to measure BER greater than:
BER better than
1 E-09
1 E-08
1 E-07
1 E-06
1 E-05
In statistics you usually have to take about 25 samples to be sure. The time given in the table above is the equivalent
of 1 sample.
Average Bit Error Rate (AVG BER): The ratio of the number of bit errors counted on the number of data bits
examined since the beginning of the test.
Average Block Error Rate (AVG BLER): The ratio of the number of bit errors counted to the number of data
bits examined since the beginning of the test.
Pattern Slips (PAT SLIP): The number of occurrences since the beginning of the test where data bits have
been added to or deleted from the received pattern
Clock Slip: Clock Slip is a timing problem that occurs when two networks meet. Sooner or later when
signals, which originated in a distant country, are brought into the network there are going to be speed
discrepancies because the networks will probably be operating at a rate controlled by their own countrys
master clock oscillator. When this occurs, the network experiences a problem because one of two situations
is possible:
1. Incoming traffic is too fast: The odd incoming traffic bit will be lost occasionally, resulting in errors
being created and passed out to end users.
2. Incoming traffic is too slow: In this situation an occasional incoming traffic bit will be repeated
resulting in errors being created and passed out to end users.
There are ways of dealing with these situations to minimize the error rate. One way is the use of BUFFERS
which are often installed at the earth station satellite modem.
32
End-to-End Testing: Quickly isolate any problem to a specific direction by analyzing the performance of an
entire digital link in both directions. Full-duplex end-to-end testing also serves as an excellent analysis of all
circuits and equipment within the network.
Out-of-Service Testing: Perform precise analysis of your circuits and equipment by removing live traffic from
the digital link. The (Fireberd) Data Analyzer offers a variety of bit error results and statistics for the most
accurate measurement of circuit performance by any test instrument.
Loop back Testing: Loop back testing is ideal as a quick check of circuit performance or when isolating faulty
equipment. The (Fireberd) Data Analyzer supports all standard T1, DDS, and data communications loop
backs.
33
34
5
6
Margin Test
BER Test
9
10
11
12
UPS Test
Antenna De-icing Test
Overall Services Test
Submitting of Site Acceptance Test
Optional Tests (if mux is installed)
13
14
15
16
Purpose
To verify quality of the cable and connectors
To verify value of cable attenuation
To guarantee correct input level to radio (TX)
To verify that antenna has been correctly installed
To guarantee that antenna and electronics meet specs
To guarantee correct value of EIRP (TX level)
To guarantee correct cross-polarization setting
To confirm proper modulator and demodulator operation
To determine Modem output level to compensate cable loss
and nominal transmit level
To verify value of fixed RX attenuator
To guarantee correct modem RF input level
To verify value of fixed RX attenuator
To Verify that the TX levels of the individual modulators and
transmitters, are configured in such a way that the radiated
power will be at the nominal power level regardless of what
transmitter or modulator is activated by the redundant
subsystem.
To verify minimum link margin
To verify minimum BER and Eb/No values
To guarantee remote access availability
To verify modem/radio access
Connectivity (IP addresses reachable)
Ping response time
FTP throughput
Customer specific application test
To check duration of UPS meets specs
To check antenna de-icing system
Connectivity and Availability
To be well documented
Connectivity
Objective quality criteria (drop outs, echo cancellation)
Availability and Connectivity
Objective quality criteria (drop outs, echo cancellation)
Subjective quality (volume level, background noise)
Availability and Connectivity
Availability and Connectivity
Objective quality criteria (Stability, drop outs, etc,)
Subjective quality of video
The new station should not generate any harmful interference with existing services
The polarization of the transmit carrier must be correct
Carrier frequencies must be correct
Transmit power must be according to the link budget results
The carrier must not exceed its allocated bandwidth
The ODU must be operating below the radio saturation point (back off)
35
Make sure you have a site specific Antenna and Radio Configuration (ARC) Sheet. This ARC sheet which is a
part of the Field Installation Documentation is the full responsibility of the satellite service provider
Contact the Satellite Control Center at least 24 hours prior to the actual antenna line-up to schedule your action.
Inform the Satellite Control Center about the site-specific details as name of the customer and the site code (or
carrier ID). Confirm transmit and receive frequencies.
Build the antenna according to the "Antenna Assembly Procedure,"
Point the antenna to the correct satellite.
Set azimuth and elevation.
Allow the radio to warm up for at least 15 minutes before any transmission.
Call the Satellite Control Center and act in accordance with their instructions.
Place the inclinometer on the metal frame at the rear of the antenna.
Adjust the elevation until the inclinometer indicates the correct value. Be advised that if you are off the correct
elevation you will never find the satellite. Bigger apertures require more accuracy.
Note: The Antenna and Radio configuration sheet gives you the true elevation (or the elevation for a prime focus
antenna). Many companies prefer the use of offset antennas. To achieve the correct inclinometer readout simply
subtract the antenna offset from the elevation given in the Field Installation Documentation.
Antenna Offset Examples
Andrew 0.96m
Andrew 1.2m
Andrew 1.8m
Prodelin 1.8m
Andrew 2.4m
Prodelin 2.4m
Prodelin 3.8m
1 piece 0.875f/d
1 Piece 0.875f/d
1 piece 0.6f/d
1 piece 0.6f/d
2 piece 0.6f/d
4 piece 0.8f/d
4 piece 0.6f/d
15.40
16.97
22.62
22.30
22.62
17.35
22.62
Azimuth
Azimuth can be measured using a compass. However, a compass doesn't work well near steel obstructions and
frameworks commonly found in buildings. Strong magnetic fields dramatically affect compass readings as well. This
is called deviation. Besides a compass always points at the Magnetic North which is officially Badhurst, Canada. The
given azimuth in the Antenna and Radio Configuration sheet always refers to the Geographic North. This means that
you always have to deal with a difference between the Magnetic North and the Geographic North. This is called the
variation and depends very much on where you are on Earth. To find the true azimuth you first must subtract or add
the variation to your compass reading.
36
Read the compass at ground level. Stay away from motors and large steel constructions.
Identify a landmark in the assigned azimuth pointing direction and refer to the landmark when pointing the
antenna.
Connect the spectrum analyzer to the RECEIVE IF OUTPUT of the radio. Leave the TRANSMIT IF INPUT
unconnected preferable terminated.
Hook up a laptop to the radio.
Connect power to the radio and program the radio receive center frequency for one of the pilot carriers on the
satellite. As an example Telstar 11 pilot carriers can be found on:
Pilot Frequency
[kHz] / polarization
12 528 000 / V
Eutelsat
Spectrum Analyzer
Center Freq. [MHz]
70.000
11 656 260 / V
Panamsat / Intelsat
11656000
70.260
11 728 000 / H
Noram
11728000
70.000
Type of Radio
37
Determine the pilot carrier you need. Set up the spectrum analyzer center frequency according to the table. Use
a span of 30 MHz and maximum sensitivity.
Check all the cables, connectors and check the LNC is working according to your expectations (e.g. a SSE LNC
shows you a noise level of -35 dBm on the spectrum analyzer).
Move the antenna slowly (not faster than two degrees per second) from the left to the right. Do this while looking
at the spectrum analyzer.
If you "hit" the satellite a bunch of signals will appear on the spectrum analyzer. You will also notice that the
noise floor is changed. If you don't see any changes at all check the elevation of your antenna and repeat the
previous steps.
Since you are only interested in the pilot carrier, decrease the span of the spectrum analyzer. If the pilot carrier
shows up on the spectrum analyzer center frequency you can be pretty sure that you are "on" the Telstar 11
satellite.
Top the level of the pilot roughly. The C/N should be better than 30 dB.
Do a side lobe performance test. Turn the antenna very slowly off the satellite (you can do this by either moving
the antenna to the left or to the right). The level of the carrier will drop dramatically. As you continue moving in
the same direction it will come up again. This is the first side lobe and its level is about 15 dB below that from the
main lobe. If you go any further you will find a second lobe and probably a third. Do the same but now for the
opposite direction. The antenna radiation pattern should be symmetrical. If this is not the case the antenna is
probably mounted in the wrong way or defective. If you leave this situation as it is the antenna will radiate energy
in undesired directions, will not meet its cross-pol requirements, and in case of receiving you will face a bad G/T.
Top the level of the pilot. Go for the best result. Do this by fine-tuning azimuth and elevation. Consider
decreasing the dB/div of your spectrum analyzer into 1 or 2 dB/div.
Secure azimuth and elevation.
Find a minimum for the pilot level. Do this by adjusting the polarizer (position of the feed) only, In most of the
cases you will find two notches. Choose the one, which gives you the best results (the difference between
minimum and maximum should be at least 35 dB). Mark this position on the donut and move the feed exactly
90. The level of your pilot carrier is topped now and you are receiving exactly the polarization in which the pilot
carrier comes down.
If the downlink polarization given in the ARC sheet is opposite of the pilot polarization then set the polarizer in its
correct position (90 swing).
TEKTRONIX 2711
70Mhz
span 100Khz/div
m -17dbm
5db/div
30 Khz RBW
Ref : -10dbm
Pilot Telstar 11
12.528 Ghz Vert. pol.
video filter on
15 db
30 db s/n carrier
300Khz
200Khz
Example only: Pilot Level on Telstar 11 with Radio gain 85dB on a 2.4 Prodelin Antenna
38
15.40
16.97
22.62
22.30
22.62
17.35
22.62
Azimuth
Azimuth can be measured using a compass. However, a compass doesn't work well near steel obstructions and
frameworks commonly found in buildings. Strong magnetic fields dramatically affect compass readings as well. This
is called deviation. Besides a compass always points at the Magnetic North, which is officially Badhurst, Canada. The
given azimuth in the Antenna and Radio Configuration sheet always refers to the Geographic North. This means that
you always have to deal with a difference between the Magnetic North and the Geographic North. This is called the
variation and depends very much on where you are on Earth. To find the true azimuth you first must subtract or add
the variation to your compass reading.
39
Read the compass at ground level. Stay away from motors and large steel constructions.
Identify a landmark in the assigned azimuth pointing direction and refer to the landmark when pointing the
antenna.
Since the LNB is powered with DC over coax it is not possible to connect the spectrum analyzer straight to the
LNB. Connect the spectrum analyzer to the monitor output of the receiver. If your receiver does not support a
monitor output use a sufficient inserter (ordinary splitters can't be used). Be very careful not to feed the spectrum
analyzer with DC power. In most of the cases you will blow up the spectrum analyzer input immediately.
Program the spectrum analyzer center frequency for one of the pilot carriers on the satellite. Use a wide span
and maximum sensitivity.
11 656 260 / V
11 728 000 / H
Noram
Type of LNB
LNB Band
LNB Local
Oscillator
[GHz]
LNB Output
Frequency
[MHz]
LNB
Bandwidth
[MHz]
Noram
Euro Low
Euro High
11.70 - 12.20
10.95 - 11.70
12.25 - 12.75
10.75
10.00
11.30
950 - 1450
950 - 1700
950 - 1450
500
750
500
T11 pilot
after down
conversion
[MHz]
978
1656.26
1228
40
Move the antenna slowly (not faster than two degrees per second) from the left to the right. Move the antenna
while looking at the spectrum analyzer.
If you "hit" the satellite a bunch of signals will appear on the spectrum analyzer. You will also notice that the
noise floor is changed. If you don't see any changes at all check the elevation of your antenna and repeat the
previous steps.
Since you are only interested in the pilot carrier decrease the span of the spectrum analyzer. When using a DRO
LNB (a LNB with a free running local oscillator) and you bring your spectrum analyzer back to a very narrow
span you will see that the pilot carrier is not stable. This is normal.
Top the level of the pilot roughly. The C/N of the pilot carrier should now be better than 20 dB.
If the installation has to transmit as well do a side lobe performance test. Turn the antenna very slowly off the
satellite (you can do this by either moving the antenna to the left or to the right). The level of the carrier will drop
dramatically. As you continue moving in the same direction it will come up again. This is the first side lobe and its
level is about 15 dB below that from the main lobe. If you go any further you will find a second lobe and probably
a third. Do the same but now for the opposite direction. This should be symmetrical. If this is not the case the
antenna is probably mounted in the wrong way or defective. If you leave this situation as it is the antenna will
radiate energy in undesired directions, will not meet its cross-pol requirements, and in case of receiving you will
face a bad G/T.
Top the level of the pilot. Go for the best result. Do this by fine-tuning azimuth and elevation. Consider
decreasing the dB/div of your spectrum analyzer into 1 or 2 dB/div.
Secure azimuth and elevation.
Find a minimum for the pilot level. Do this by adjusting the polarizer (position of the feed) only, In most of the
cases you will find two notches. Choose the one, which gives you the best results (the difference between
minimum and maximum should be at least 35 dB). Mark this position on the donut and move the feed exactly
90. The level of your pilot carrier is topped now and you are receiving exactly the polarization in which the pilot
carrier comes down.
If the downlink polarization given in the ARC sheet is opposite of the pilot polarization then set the polarizer in its
correct position (90 swing).
Contact the Satellite Control Center at least 24 hours prior to the actual antenna line-up to schedule the cross-pol
adjustment. Inform the Satellite Control Center about the site code (or carrier ID which is on your Antenna and
Radio Configuration Sheet) and the name of the customer.
Confirm the transmit and receive frequencies.
Check if all the antenna bolts and nuts are tightened firmly. Check all the ballast is in place.
Allow the radio to warm up for at least 15 minutes before any transmission.
Program the radio transmit center frequency for the test frequency. TX must be switched off!
Configure the satellite modem for:
TX frequency: 70 MHz
Pure carrier (switched off)
TX carrier level: -25 dBm
Check all the cables and connectors. Connect the modulator output to the radio input. Use attenuators, which are
easy to remove. At least 30 dB to start with.
At the scheduled time, contact the Satellite Control Center and ask them to assist you on setting the cross-pol
isolation. The Satellite Control Center will provide you with a test frequency.
If you are in the possibility so see the downlink resulting from the uplink this frequency should be clean. Program
the radio for a receive center frequency and the spectrum analyzer for 70 MHz.
41
Bring up a carrier if the Satellite Control Center tells you to do this. Give the TXON command to radio and
modem.
Adjust transmit level according to the directions of the Satellite Control Center.
If you can see your own down link, go back to your azimuth and elevation settings. Set your spectrum analyzer
for 1 dB/division. Leave the transmitter on and top the level of your own downlink. You probably will gain another
0.5 dB of signal strength. When you are finished call the Satellite Control Center for the final. If you cannot see
your own downlink you will do this together with the Satellite Control Center.
To achieve an optimum in cross-pole isolation the Satellite Control Center will ask you to adjust the position of
the feed. Do this very gentle since a small change in the position of the feed gives you an enormous change in
cross-pol isolation.
When a maximum of isolation is achieved (better than 30 dB) secure the feed. The Satellite Control Center will
now recheck the isolation. If the results meet the requirements you will be asked to bring the carrier down and to
prepare yourself for a level setting test on the assigned frequency.
42
Gauge Wire
10 gauge or greater diameter
10 gauge or greater diameter
10 gauge or greater diameter
10 gauge or greater diameter
10 gauge or greater diameter
6 gauge or greater diameter
It should be noted that the next greater diameter gauge wire from number 10 gauge is number 8 gauge, that is, a
larger diameter wire has a smaller gauge number.
43
Do Not
Do not ground to any branch circuit conduit or any conduit on the load (or output) side of the service equipment
enclosure (power distribution panel). The metallic power service raceway is defined as the input power service
conduit, which is on the input side of the service equipment enclosure.
Do not use the shield of the coaxial cable as the main grounding wire between the indoor and outdoor unit.
Do not ground the antenna to an air conditioning unit. Grounding to an air conditioner mounting frame is not
recommended because the frame may not be connected to building steel, and may provide a ground loop condition.
Ohmmeter measurement will not detect a ground loop condition, since the EFL is connected to ground via the third
wire of the indoor unit power cord, and the air conditioner metal frame is connected to ground via the air conditioner
third wire. A low resistance value will be measured even though the metal frame is floating. The ground wire should
be routed securely to prevent a possible tripping hazard. If possible, route the ground wire along the EFL cable to the
point of entry.
Do not connect the building ground to the lightning protection. This is to avoid ground loops.
The building lightning protection is not equal to the building ground!
Ground loops
The Situation
GND
main gnd
UPS
Buildig
ground
Rack
Barrier
strip
De-ice GND
Rack
SSE
Radio
SLP
Box
Antenna
GNG
De-ice
System
Buildig
ground
Lightning Protection
What is going to happen:
V (lightning discharge) = dV/t. As the length of the lightning earth is a long cable => high impedance for
dV/t. This means that our equipment can be damaged.
44
Many lightning flashes consist of multiple discharges, making this well-known natural phenomenon Nature's Most
Destructive Force.
Myths & facts
Many people believe they have lightning protection if the antenna on the building rooftop is "grounded". Even if an
expert had properly grounded the antenna, only the antenna would be protected. The major portion of the building is
still unprotected. More importantly, when struck by lightning, the grounded antenna may very well introduce side
flashing to other grounded metal objects within the building. The ignition of combustibles may result.
Another myth is that tall trees around a building will protect it from lightning. Actually, more often than not, when
lightning strikes such a tree it will only follow the tree a short distance before "jumping" to some grounded metal item
in or on the building. Larger branches over a house present a double peril, in that they could come crashing into the
building should a lightning bolt tear them off.
Lightning does strike the same place twice, sometimes more than once during the same storm. If it has struck once,
chances are it will strike again.
45
The building owner is responsible for the lightning protection on his building and in no case the VSAT technician is
allowed to commission any lightning protection system.
The next lightning protection requirements are typical for the USA but may very well do in other parts of the world
since almost every country has a similar notified body.
A complete lightning protection system shall be installed by a firm actively engaged in the installation of Master
Labelled Lightning Protection Systems and shall be so listed by Underwriters Laboratories Inc. The completed system
shall comply with the latest editions of the Installation Requirements for Lightning Protection Systems, UL96A and the
National Fire Protection Association's Lightning Protection Code, NFPA 780.
Lightning protection is the responsibility of the building owner and is basically a very thick metal pipe on top of the
antenna. The minimum height of this pipe is the height where the antenna is covered totally (see drawing). After a
lightning strike the equipment is gone anyway but it hopefully will prevent you from fire.
46
This means that most failures can be avoided and outages can be substantially reduced by the implementation of a
good maintenance policy. A proper inspection and maintenance program is a form of insurance.
Maintaining an earth station antenna is much less costly than to repairing one that has failed.
47
Inspect the total appearance of the equipment, including radio, LNC, feedhorn and de-ice.
Inspect the antenna mount hardware
Inspect the ground connections
Inspect the power equipment and facilities
Inspect the IF equipment and terminal equipment (including modems, mux and M&C Equipment)
Inspect the enclosures
Inspect the cables and connections
Inspect areas exposed to the weather to insure they are adequately waterproofed
Evaluate antennas overall performance
Reliable and effective maintenance depends upon good test equipment, which is regularly calibrated, in accordance
with manufacturers recommendations.
48
49
All
Mount Hardware
All
Impedance
Leads
Ground Connection
Resistance
Reflector and Mount Openings
Radio
50
Antenna
Indoor equipment
Maintain
If galvanized, remove rust: replace or
treat with zinc-rich paint.
Repaint where peeling, flaking or fading.
Install extra ballast if necessary and
notify customer or building owner of
possible roof damage or leakage.
Tighten, replace or reinstall hardware.
Tighten or replace hardware.
Remove sharp bends in leads.
Verify proper resistance; add grounding
if needed.
Repair/seal openings as required.
Repair as necessary.
Perform insertion loss tests.
Replace cables if out of spec.
Replace damaged connector hardware.
Replace waterproof tape.
Verify with multi-meter
Replace if missing, rusted or corroded
Talk to the NOC. Check for moisture, dry
out as necessary. Wipe surface with
damp cloth to remove dirt and dust.
Clean, repair
51
Inaccurate antenna pointing: The most common causes for antenna deflection and resulting beam pointing
errors are:
o High winds or gusting wind conditions
o Settling of the antenna mounting
o Loosening of the assembly due to weather and wind conditions
o Flexing of the supporting structure. The allowable deflection varies inversely with the size of the
antenna reflector. As an example for a 2.4m antenna this is 0.15 degrees
Loose bolts/nuts on the antenna resulting in:
o Antenna looses pointing
o Antenna diagram is not as specified since the reflector is not kept in shape properly with loose bolts
Loosing pointing when tightening Elevation/azimuth bolts resulting in:
o Low quality of service
o Interference with adjacent satellites
Low cross-polarization isolation resulting in:
o Signal of the site is also seen in the opposite pole
o Interference with other systems operating on the other pole
o Low power efficiency of the VSAT station (only with very bad settings)
Wrong transmit frequency settings
o Signal is overlapping with other services
o Interrupt of other services
Wrong receive frequency settings
o Station is not able to receive
o At least no impact on other systems operating on the satellite