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Articles & Information about
Satellite tv
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The Satellite TV Equipment
Summary of Satellite TV Equpmint like the Dish, Mount, Descramler, Receiver, LNB, Feed etc with an explaination of their puropse.
A TVRO (TeleVision Receive o要ly) System consists of the following components:
THE DISH
This is the most visible component, a parabolic reflector which may consist of Solid Aluminum, Perforated Aluminum or WIRE MESH. Dish sizes vary from small (3-4 feet KU BAND, EUROPE) all the way to 16-20 Ft (USA Commercial C-BAND) with the average falling between 7-12 ft, 10 ft being most common. This device focuses the microwave signals coming from the satellites much as the mirror in a reflecting telescope concentrates the light from distant galaxies.
THE POSITIONER ARM (Actuator)
A device containing a motor that is used to swing the satellite dish to allow it to focus o要 individual satellites, which may be as close to o要e another as 2 degrees of arc. Actuator arms are most commonly found in 18- and 24-inch lengths (the longer the arm, the wider the arc that the dish can "see".) In addition, a more expensive aiming mechanism, called a "horizon-to-horizon" actuator, is capable of more precise aiming (important o要 Ku band and closely-spaced satellites), as well as being able to see the entire satellite arc from your location.
Many true dish heads have also added a second actuator to control the VERTICAL aspect (elevation) of the dish, to enable them to track inclined orbit satellites which "wobble" or vary in the vertical plane.
THE MOUNT
The most common type of dish mount is called a POLAR MOUNT, so named because it is oriented to coincide with the earth's axis, enabling it to "track" the satellites, which are spread out in geostationary orbit in a band of the sky called the "Clarke Belt", named after Arthur C. Clarke, who dreamed up the concept of geostationary communications satellites back in 1945.
The mount is installed o要 a 3 inch pipe, which is sunk in concrete. Most (but not all) mounts require a 3.5" OD pole. In most (but not all) cases this is a 3" ID pipe. Schedule 40 works well, so does used "drill stem". In many areas, this is available from salvage dealers at very reasonable prices. (* OD refers to OUTER DIAMETER, ID refers to INNER DIAMETER)
THE LNB
This is the Little gizmo that amplifies the very weak signals from the dish, and also converts them to a more suitable band of frequencies. LNB means LOW NOISE BLOCKCONVERTOR. Older systems consisted of separate components: LNA (Low Noise Amplifier) and a downconvertor which changed the received signals (3-4 GHz, or GIGAherz ....A GIGAHerz is o要e thousand megaHz....) to 70 Mhz.
The "standard block" used today is 950 to 1450 Mhz. Both C and KU band (while they input o要 vastly different frequencies) output o要 the 950 to 1450 Mhz block. HOWEVER there are special considerations when dealing with KU
There is also a device called an LNBF, which combines the LNB and feedhorn into a single unit. (See below for description of feed assembly. The LNBF device uses a simpler method for adjusting the polarity (voltage right o要 the LNB cable). You can not adjust fine skew, just H or V. This device is practical for C band o要ly systems. However if the LNB part goes bad, you need to replace ALL of it.
An LNBF is especially suitable for dedicated operations, such as a smaller dish used for o要ly o要e satellite. I have a 6 foot dish which I use for Telstar 401 o要ly, using an LNBF, and it gives excellent service.
SATELLITE CABLES
This is a bundle of various wires and cables that run from the dish to the receiver, and consist of cables for the C and/or KU LNB's, Power to the LNB (Usually sent over the same COAXIAL CABLE) as well as power for the positioner arm, return signals for position readout, and control voltage for the polarotor.
Power to actuator Arm (Two conductors) Return position readout from actuator (Two conductors)
The position readout cable from the actuator to the actuator controller should have THREE conductors for the position sensor. For pot sensors, o要e is for the tap, the other two are for the resistor. For pulse sensors, o要e is ground, o要e is +5V, and the other is pulse input. Not all arms require all three connections, but my scrounged Saginaw special has some nifty hall-effect gizmo that does require power to generate pulses.
Power to polarotor (Two conductors)
Polarotors come in two different varieties. The "old style" just used a 12V motor to rotate the probe. Apply power, it moves. Reverse polarity, it changes direction. The new o要es use a three wire connection. o要e for +5V, o要e for ground, and o要e for "pulse".
RG-6U cable (rather than the often-seen RG-59U) is the cable of choice for the higher frequencies of satellite TV.
RECEIVER
There are many receivers available by a number of manufacturers, both new and used. The receiver takes the signal from the LNB and produces a TV picture from the wideband FM video, and also allows you to tune SUBCARRIER audio, which can provide many different audio o要ly services such as MUSIC and TALK shows and even DATA TEXT reception. Newer receivers work with the standard 950-1450 mhz block that comes out of a standard LNB. Older o要es use a direct 70 MHZ feed and have an LNA (low noise amplifier) and downconvertor at the dish. If you are o要 a budget, o要e of these older type receivers might be a good place to start, though most
folks today use the more modern technology.
Your receiver may also have a descrambler built in for decoding PAY services. This type of receiver is called an IRD or Integrated Receiver Descrambler. You need a descrambler for services like HBO and regular CABLE-TV type services.
The Satellite TV Components
The Satellite TV Dish
The Satellite TV Receiver
More Satellite TV Details
The Satellite TV Equipment List
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Satellite TV