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Newsgroups: rec.video.satellite
Date:         Thu, 7 Jan 1993 10:16:14 +1200
From:         "S. Cathcart" <S.Cathcart@MASSEY.AC.NZ>
Subject:      Re: Satellite info please

Good Morning,

The following may be of some interest to you.

SATELLITE TELEVISION - done the DOWN UNDER WAY.

INTRODUCTION:
Satellite television is the amazing methodology of bringing international
television entertainment to home viewers direct from orbiting satellites
located high above the equator in the Pacific ocean region (POR). Each
satellite can "see" 40% of the earth's surface, in theory only three
satellites are required located over the Indian (IOR), Pacific (POR) &
Altantic Oceans (AOR) cover our entire planet as outlined by Arther C Clarke
in 1945. Satellites have a design lifetime of 10 years or more and it is
ultimately limited by the amount of on board fuel available to keep the
satellite "on station" although some ofthe older satellites are now drifting
above and below their assigned position making earth bound tracking essential
for max performance, this has been brought about by the failure to replace
aging satellites fast enough through the grounding of the US shuttles
following the Challenger disaster. We use TV satellites that are parked in
internationally allocated positions on the geostationary belt sometimes known
as the Clarke belt or GSO (Geostationary Orbit) - from this position the
satellites appear stationary when viewed from earth, this phenomenon is
achieved by placing the satellite in an orbit 35,786km (22,300 miles) above
the earth and traveling at 3075m/sec.
We have access to four INTELSAT Satellites parked on the Clarke belt at 183,
180, 177 & 174 degrees East with some transmitting TV programmes together with
three Australian domestic satellites AUSSAT 1,2 & 3, these three satellites
are due to be replaced 1992/3.
OPTUS have brought on line its B1 (replacing A1) satellite with disastrous
results for all NZ OPTUS Ku viewers - B1 being more powerful than its
predecessor many thought that signals from B1 would be stronger in NZ but its
"foot print" is more sharply defined meaning little or no signal spills over
(spillover) into NZ. OPTUS saw the loss of it A2 replacement satellite (B2)
when it failed to reach its prescribed orbit.
The three-axis gyroscopic spin stabilised INTELSAT V series of satellites
serve the Pacific basin transmitting signals from 8.5w TWTA's (Traveling Wave
Tubes Amplifiers) giving a global beam (or "footprint") edge of approx 25dbw.
A "footprint" simply defines the illumination pattern from the satellite as it
fails on the earth, this can take many forms including zone, global, East &
West hemispherical and spot beams. No matter what type of beam pattern is
transmitted by the satellite the signal is always strongest in the centre
or as it is sometimes called the "boresight", the signal reduces as it moves
away from the "boresight". The signal strength called EIRP (effective
isotropic radiated power) is plotted on a footprint" map in contour lines
expressed in dbw (decibels referenced to 1 watt)
The series V satellites contain 27 "transponders" each has an "up-link"
frequency in the 6gHz band which receives signals from earth based up-link
stations (ie Warkworth) the output of this receiver is processed and then
linked to the "down-link" transmitter on 4gHz.
The OPTUS satellites each with fifteen 45mHz wide transponders are not
generally received in NZ using "domestic" equipment because of their very
focused transmitting beams directed at Australia and use the "Ku" band to
transmit their signals, furthermore most signals are B-Mac and are generally
encoded.  However the new OPUS B1 has eight transponders capable of serving
New Zealand, three are high power and will require receiving dishes of 1-2m in
diameter and the remainder are lower powered requiring dishes of up 3m for
good TV reception. No plans have been announced to use these transponders for
a Direct Broadcast Satellite (DBS) service to New Zealand.
Russian TV programming can also be received in NZ from the Russian GORIZONT
(Russian for horizon) & Statsionar (Russian for stationary) Satellite.
A interesting challenge for the TVRO enthusiast is seeking out the non-video
"hidden Signals" which include audio subcarriers, teletype, news/press
services, stock market reports, teletext, single channel per carrier (SCPC -
Single Channel Per Carrier) multiplex data, SiS (Sound in Sync) and telephone
channels etc, etc.

PROGRAMMING:
Satellite television offers a wide variety of video and audio programming
including 24 hour sports, news, documentaries and political comment.
Japanese, Russian and French (RFO) language programes are regularly observed.
Audio programming includes light musical, religious, pop and serious music,
BBC FM service and the Voice of America (VOA).
Regularly seen TV channels are: American TV channels ABC, NBC, CBS, CNN, CNN
International, C-Span, ESPN (encoded), Channel Nine (Aust), NHK (Japan), BBC
Asia, BBC's World TV ASIAN service & ITN, TVNZ's service to the Pacific Is and
various itinerate feeds. The BBC World TV service to the Pacific is expected
before the end of 1993 also we hear the Australian ABC is planning a early
1993 launch of its Pacific TV service.

LNB:
The LNB (Low Noise Block) is the single most important item in a typical TVRO
installation as it is the most significant contributor of system noise, modern
LNB's have a NF (Noise Figure - noise temperature) of 26 degrees K (Kelvin) or
.380db for "C Band" applications and .9db or 70 degrees K NF for "Ku Band"
applications. Degrees Kelvin is the temperature above absolute zero - the
temperature that all molecular activity stops, absolute zero equates to -273
degrees C or -459 degrees F. The LNB is the first active or electronic device
in the TVRO RF signal processing chain. It performs two functions, one is to
provide very low noise amplification and the other to convert the 4gHz or 12gHz
signal to an "first" IF of 950 to 1750mHz.
A typical LNB has a gain of 55 to 65db of RF signal gain and an IF frequency of
950 to 1750mHz with a very stable fixed dielectrically resonant local
oscillator being on the "high" side 5.1gHz for "C Band" and on the "low side"
for "Ku Band" LNB's, frequency stability is +/- 1.5mHz for both bands.
Performance is enhanced by using the latest technology including P-HEMT
(Pseudo-Morphic High Electron Mobility Transistor) and SMT ( Surface Mounted
Technology) 18vDC powering for these units is feed from the TVRO RX to the LNB
via the IF cable.

FEED HORN:
The feed horn is a precision wideband antenna mounted at the dish focal point
that collects the reflected signal from the dish surface. All "C Band" TV
transmissions from Intelsat Satellites are circularly polarised either Right
Hand (RHCP) or Left Hand (LHCP).
To modify a standard Chaparral Super Feed II Linear feed horn for RHCP or LHCP
a slab of teflon is installed inside the feed horn throat at 45 degrees
in-relation to the LNB pickup probe.

ANTENNA:
The antenna, usually shaped in a parabolic curve, prime focus dish is a
precisely curved metallic surface so that the incoming signal is reflected
from the surface and focused at one point which is known as the focal point,
at this point we position the feed horn who's function is to feed this very
weak signal onto the Low Noise Amplifier (LNB) for further amplification.
There are many factors that influence the f/D ratio of a TVRO dish, in
practice it is usually .36 to .375. The minimum antenna gain required for
good "C Band" TVRO pictures is at least 42dbi (db antenna gain relative to an
isotropic source) which is obtained by using a 12ft mesh dish with good
parabolic accuracy - within 2mm over the entire surface area. Commercial
mesh dish has a efficiency of >65%. The ability of an antenna to form a
tight focal point is related in part to its gain, this will influence the
quality of picture you receive - higher the antenna gain the better the
picture/sound.
Satellite TV antennas are constructed from many materials, including
fiberglass, metal (steel & aluminum) or wood or a combination of materials.
All have one thing in common:
a curved metallic surface for reflecting and focusing the signal to the feed
horn.
Fiberglass antennas sandwich metal foil or screen inside the fiberglass or
paint the reflecting surface with special "reflecting" paint. Steel and
aluminum can be used as a reflective surface in either solid form or as open
mesh screening. The framework can be made of steel, aluminum, wood or
fiberglass just as long as a well defined curved metallic surface is
maintained.
Open-mesh antenna are generally 4 times cheaper than all other types of dish
antennas and are generally the choice of most users. However, the screen
surface is more easily damaged by hail, vandalism or even strong scrorly winds.
Open-mesh antennas can be manufactured much lighter without affecting overall
stability.
The strength and rigidity of  the outer circumference is very important
because this is where much of the signal is reflected from. Fiberglass is
affected over time by solar radiation, which is why fiberglass antennas are
always white or other light colours, any dark colour would only hasten the
deterioration.

TRACKING:
Azimuth and Elevation are the two basic coordinates required to aim the dish
to satellites parked on the "Clarke Belt", once you have the unique pair of
coordinates for a given satellite you can use a compass to accurately align
your dish, a compass will give you magnetic bearings, to correct to a "true"
heading you will need to subtract the magnetic deviation for your area, if
this is not known call your airport control tower for the correct offset.
Elevation setting is best done by placing a "inclinometer" on the back plate
of your dish ie the same plane as the outer rim of your dish, set the
elevation to the figure supplied by the dish supplier or a figure that is
equal to the polar axis angle plus the declination offset for your area. If
an inclinometer is not available you can use a protractor and plumb bulb.
Declination is the offset angle between the polar axis and the dish which
enables the dish to precisely track the Clarke Belt. The declination angle at
any site is defined by the latitude at that location. The declination setting
is usually given by the supplier - in NZ the declination is between 5 to 7
degrees depending on the latitude of the site.
The elevation angle is the sum of the polar axis angle and the declination
offset angle.

DISH MOUNT & ALIGNMENT:
Your dish pole mount is usually a length of 31/2" or 4" OD of thick wall
galvanised steam pipe set in concrete, the size of pad depends on the dish
diameter. Concrete is also poured inside the pole mount pipe for added
strength and less whipping, this is especially important if Ku band reception
is anticated. Additional strength can be obtained by affixing two support
members from just below the polar mount at an angle of 45 degrees behind the
dish mount pole. Before the concrete is poured it is vitally important that the
dish mount pole is plumb ie vertical in all planes.
It is not recommended that large dish's not be mounted on roof's unless a
registered engineer has certified such a installation.

TVRO RECEIVER:
The satellite receiver takes the amplified satellite IF signal with is between
-60dbm - -30dbm from the feed horn/LNB, then delivers a Base band (based band
signal is the un-clamped and un-filtered output of the TVRO RX demodulator
containing video information as well as all the transmitted subcarriers) or
composite Video signal and a audio signal suitable for viewing on your
television set or multi-standard receiver or monitor. The  Satellite TV
receiver is basically the "second" IF at 479.5mHz or 70mHz as in older
receivers and use a SAW filter/s to achieve a suitable selectivity usually
36,24,18 or 12mHz bandwidth depending on how the transponder is configured
for full or half transponder operation.
Most TVRO receivers are microprocessor controlled and use digital PLL
(phase lock loop) for both input and sound subcarrier tuning. The quality of
a Satellite TV receiver lies in its ability to produce a good pictures from
very weak signals, ie as little as -112 dbwm2 PFD (Power Flux Density) is
available which translates to 6 picowatts of signal power falling on every
square metre of surface area and not so much in all the extra gadgetry.
A domestic TV receiver as used in most households is not suitable to directly
receive satellite TV transmissions because satellite signals are very weak
(as much as 165bdm2 is lost between the satellite and your TVRO site -
Warkworth use a 30 meter (100ft+) dish to obtain TV pictures suitable for
rebroadcast where the TV enthusiast is generally using a 12ft dish. Present
day TV receivers are suitable for receiving programmes on VHF and UHF
frequencies, the satellite transmits in the SHF band of frequencies (4gHz
& 12gHz). The major difference is that our domestic TV receivers use AM picture
modulation and FM sound modulation where-is Satellite TV uses wide band FM sound
deviation of typically +/- 150kHz & a vision deviation of 40mHz. The frequency
the audio subcarrier is transmitted varies between 6mHz & 8mHz and use
different de-emphasis and pre-emphasis characteristics from the normal
domestic 50us standard.
A further difference is that the transmitted signal from the satellite is
"dithered/wobbled" up and down in frequency over a range of 1mHz at a rate of
25Hz - this concept is referred to as "energy dispersal".
Because we are intercepting international TV signals we need to consider TV
"Standards". There are many different video standards in the world today
including NTSC (National Television Standards Committee) which is used by
USA, Canada, Japan el at, PAL (Phase Alternate Line) is used by European
countries, Australia, England, NZ et at, SECAM (Sequence Couleur a Memoire) is
used by France, USSR el at. This lack of international TV standardization can
make life for the satellite TV viewer difficult - to overcome this dilemma by
purchasing a multi-standard TV monitor/receiver for little more cost than a
domestic TV receiver.

Equipment:
A basic "domestic" system to receive "C Band" TV programmes from INTELSAT
Satellites consists of:

1.      Satellite TV Receiver WR-370 or similar - from NZ$456.36
2.      LNB (Low Noise Block Down Converter) 40K or better - NZ$789.98
3.      12ft Satellite Dish c/w Polar Mount - NZ$2,164.09
4.      Feed Horn - $486.36 or NZ$188.45
5.      Monitor and/or TV receiver - ideally multi-standard - NZ$1,200
6.      Auto Tracking system and actuator - NZ$720.00
Note: items 5 & 6 can be considered as system "upgrades"

To install a domestic Satellite TV system some technical knowledge is
required - assistance is usually available in most areas. The dish must have
a direct unobstructed view to the North (to the South in the Northen hemishere)
and elevated to approx 45 degrees - the correct aiming co-ordinates can be
obtained from your TVRO supplier for your location. Due to the large surface
area of the dish special consideration must be given to mounting the dish,
whether elevated or at ground level - in some cases it will be desirable to
seek professional advise.

Happy viewing - we have only touched the surface of this fascinating
methodology.

Selwyn Cathcart
Technical Director
Telvision Production Centre
Massey University
Palmerston North
NEW ZEALAND.

Email: S.Cathcart@massey.ac.nz
Fax No: +64-6-355-2141
Newsgroups: rec.video.satellite