
Successful downlinking of satellite programs
requires careful attention to the satellite specifications provided
by the broadcast provider and experience using the local site's
receiver equipment. Best results will occur if sites use a knowledgeable
technician to program and steer the satellite dish. If that is not
possible for each program, the personnel designated to downlink
programs should learn as much as they can about their equipment
from the technician who programs it and follow the guidance below.
Background
Satellite program providers cannot control which
satellites are used for a particular program. They have set standards
for the purchase of all satellite time, e.g., full transponder capability
and both C- and Ku-Band access. However, there are no guarantees.
Project personnel purchase satellite time from the open market.
Availability of satellite space at the time the procurement is processed
determines which satellites are used.
Downlink Test
Even if the site has determined you are capable of receiving a satellite
transmission, you should always conduct a pre-broadcast test at
least 30 minutes
before the session start time to allow for trouble shooting. The
satellite broadcasters will broadcast a test signal prior to the
actual program.
The purpose of testing your downlink during this time is to make
sure any technical problems are resolved before the session begins.
This is also the time when the uplink and satellite transponder
will be adjusted to transmit the highest quality signal. Be patient
for the first three to five minutes of the test as some fine-tuning
may be occurring at the uplink.
Once you are receiving the best possible signal, adjust the television
monitors, receiver and video recorders for accurate color and a
good picture under the actual lighting conditions you will be using
during the program. If there is an image of a person on the screen,
it is best to adjust the color so the skin tones look natural.
A few weeks before the program you will
receive information from the satellite broadcast program provider
coordinator about the technical aspects of receiving the program.
The information will include the name of the satellite and
coordinates, as well as the phone number
to call if you experience technical difficulties.
Please
note the time zone of the program and adjust the time accordingly!
Satellite Guidance
Accessing a Satellite Program.
In order to tune into a satellite program, you must have 1) a steerable
antenna capable of receiving either C- or Ku-Band satellite transmissions
and 2) the satellite coordinates designated for the particular program
you are trying to access. The coordinates specify which satellites
on the C- and KU-Bands are being used. You will need to program
your receiver with the code that matches either of these satellites,
depending on your band capability.
Programming the Analog Receiver.
Most sites have satellite receivers that can be pre-programmed to
access the various satellites in the arc over North America. It
is critical that the programming of the receiver be done correctly
and accurately. We recommend that this be done by a qualified local
technician, competent with both C- and Ku-Bands, at the time of
installation and updated annually.
Program Codes. The codes which
the technician programs into your system are not standardized system-wide.
They may vary from state to state or even from technician to technician.
For example, the satellite Telstar 4 may be coded as "T4"
in one receiver and "T1" in another. The specific codes
used are not as critical as the fact that the technician tracks
each code created and lists it in writing on a chart for you next
to the satellite name. This should be done for each and every main
satellite in the North American arc. The chart attached displays
the most widely used satellites in North America, as well as a typical
code for each. Note that the letter/number combinations can only
be used once in programming a satellite. The far left hand column
has been left blank for you to record your receiver's programmed
codes. We recommend that you/your technician complete the entire
chart, showing the codes for each satellite. Then date and post
it near your equipment, so that anyone who needs this information
about your system can easily access it.
Receiver Operator. Once your receiver
is fully and accurately programmed, it is recommended that a particular
person be designated to operate the machine at all times. An additional
person should be identified and trained as a back-up. It is also
recommended that the operator prepare a detailed, step-by-step "how-to
operate the receiver" guide for any time that the main designee
is not available.
Pre-Program Test. As soon as you
obtain the coordinates for a program, immediately verify that your
receiver is programmed for the satellite(s) specified. Then, utilize
the test time designated (normally the day prior to the broadcast)
to check the signal. Do not wait until the actual broadcast to perform
this check.
Annual Code and Satellite Check.
The satellite business is a dynamic one. New satellites are launched
and old ones inactivated all the time. For that reason, it is critical
that you have your list of codes and equipment checked by a reputable
technician once a year at a minimum. This updating process will
help to ensure that your receiver is accessing the right satellites
for your programs.
Dual C- and Ku-Band Capabilities.
Some satellites are low-powered and provide weak signals. Therefore,
it would be beneficial for each downlink site to have capability
to receive both C- and Ku-Bands. If both bands are accessible and
properly programmed, switching from one to the other will provide
you the versatility to select the stronger of the two signals, thus
providing clearer reception. If you currently do not have both C-
and Ku-Band capability, ask your technician what the cost would
be to upgrade your system. This should not require a new dish, only
hardware. The advantage of having the option to switch to a stronger,
clearer satellite band when a signal is coming in weak will generally
outweigh the cost associated with the upgrade.
Aligning an Analog Receiver
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Aligning your
satellite dish correctly is a critical step. |
It will ensure the best possible signal reception.
Take your time in completing the sequence. In many cases, your technical
staff, a rental dish vendor or other locally arranged staff will
complete the satellite antenna alignment. Knowledge of the necessary
steps will help you supervise this operation.
Tune your receiver to the proper transponder
and audio
sub-carrier frequency to receive the signal being transmitted.
We do not plan to encrypt (scramble) the broadcast, but other broadcasts
that you might receive may be scrambled.
Adjust the elevation
of the satellite dish if needed.
Adjust the azimuth
of the satellite dish if needed.
Adjust for the correct polarization,
either horizontal or vertical if needed.
Repeat items 2-4 until the video signal is sharp
and clear of static and interference. If your receiver has a signal
strength meter, this meter should indicate it is receiving the maximum
strength signal from your downlink site. This is referred to as
"peaking" the signal
strength meter.
Azimuth/Elevation
The location of the satellite in the sky from
your viewing site. You or your technical people will need to know
how high above the horizon the satellite is, which is called the
elevation. You or your technical
designee will also need to know the azimuth,
that is how far east or west in the southernly sky the satellite
is located.
Polarization
Signal polarization is either horizontal or vertical.
The signal coming from the satellite to your dish will either be
vibrating along a horizontal or vertical plane. The receiving equipment
must be adjusted to receive the correct polarization.
Audio sub-carrier
The audio portion of the videoconference is sent
along with the video signal, but on a different frequency. Selection
of the proper audio sub-carrier will allow you to hear the audio
portion of the program.
| Technical Difficulties |
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If you are not receiving a good signal
there may be downlink equipment problems, local terrestrial interference
(if using C band)
and uplink transmission problems. Some of the local technical difficulties
you may encounter are:
1. Terrestrial Interference
is usually caused by local microwave transmission for telephone
and paging systems operating on the same frequency as that of your
C band downlink.
It can vary in strength as well as how often and when it occurs.
Terrestrial interference can range from little black and white dots
that show up on the screen to complete interference and blockage
of reception. You may need a technical person to "scout' out
the source of interference.
2. Rain Attenuation
can drastically weaken the signal strength if you are receiving
the signal on a
Ku band. The result will be similar to the terrestrial interference
described above.
3. Snow on the satellite
dish, if allowed to accumulate more than four or five inches,
can interfere with the signal reception. Remove the snow with a
soft cloth or broom. A small amount of ice on the dish should not
cause any problems.
4. Sun Spots
are another common interference.
Notes: 
Most often problems are at the downlink
end. If you think there is a problem at the uplink
or with the satellite transponder,
first check other transponders on the same satellite.
If you are not receiving a clear signal on the scheduled transponder,
but are receiving a good signal from another transponder or if you
think the problems you are having are not local, call the technical
support member. The number will be provided with the satellite coordinates.
Back-up Plan
If you are unable to receive the satellite
transmission, first check with the on site technician for assistance.
If that does not work, contact technical assistance at the uplink
site. The number will be provided with the coordinates. If you are
still unable to receive the broadcast, you have a choice of two
options.
Option #1
is to listen to the broadcast on a speaker phone if it is available
from the program provider. A hard copy of all the slides may be
provided online for participants to see what the presenter is showing.
Option #2 would
be to watch the video tape at a later date if a tape is available.
Guidelines for Phone-in Questions
The phone number will be provided with each sessions
materials. It will also be displayed across the screen during times
that phone calls will be accepted. Bring one caller to the telephone.
Only one caller per site will
be accepted with each call. This means that if you have more than
one participant wishing to present questions during the call in
period, you must place each call separately. This allows other sites
access to the telephone line.
When calling in, please give the following
information:
1. Name
2. Site Location
3. Who the question is for (speaker, panel or entire group)
The Question:
Questions are screened before they go on the air in order to reduce
repetition. Some presenters will address the questions given to
them on cards, versus live. Therefore, questions could be called
in throughout the program.
Wait quietly and continue to monitor the telephone while the operator
checks the sound.
If the television audio can be heard over the telephone line, the
operator will ask that the television set be turned down before
the caller goes on the air.
When the program uses live questions, the presenter will state when
he/she is ready to receive questions. Continue to stand by the telephone
as the presenter may ask for clarification or feedback during the
answer. An "echo" effect
will result from the one-quarter second delay between the time the
word is spoken at the site and relays back on television. The echo
is normal and should be ignored.
When the presenter moves on to the next call, you will automatically
be disconnected. Hang up the telephone and re-dial to start the
process over with another caller. If the line is busy, keep trying
until the interactive portion of the program is concluded.
Questions or statements made by the viewers may or may not be representative
of the audience at large. The question-and-answer period should
benefit all viewers with the discussions that take place between
their fellow viewers across the country and expert presenters.
Satellite
Teleconferencing Terminology
C-band n. A
frequency used in satellite transmission.
Downlink n.
A satellite dish that receives a signal from a satellite transmitter.
It encompasses all the equipment at a receive site.
Ku-band n A
frequency used in satellite transmission.
Satellite Dish
n. The device that sends or receives satellite signals.
Satellite Receiver
n. A piece of equipment used to select a satellite, and the proper
transponder.
Transponder
n. The part of the satellite that receives the uplink signal and
then transmits it back to earth. EEach satellite has between 10
and 32 transponders.
Uplink n. The
satellite dish that transmits a signal up to a satellite. It is
also known as an Earth Station.
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