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Instead of block-downconverting the whole received spectrum, an SCR LNB downconverts a small section of the received signal (equivalent to the bandwidth of a single transponder on the satellite) selected according to a DiSEqC-compliant command from the receiver, to output at a fixed frequency in the IF. Up to 32 tuners can be allocated a ...
Low-noise block downconverters (LNBs) [1] are electronic devices coupled to satellite dishes for TV reception or general telecommunication that convert electromagnetic waves into digital signals that can be used to transform information into human or machine interpretable data, e.g., optical images, video, code, communications, etc.
A twin-output Duo LNB fitted to a 60 cm dish with only one output connected. (Note that this LNB is mounted using the 19.2°E feedhorn, not in accordance with SES' installation guidelines) A Duo LNB is a double low-noise block downconverter (LNB) developed by SES for the simultaneous reception of satellite television signals from both the Astra ...
In the LNB they become down converted to 950–2150 MHz, which is the frequency range allocated for the satellite service on the coaxial cable between LNBF and receiver. Lower frequencies are allocated to cable and terrestrial TV , FM radio, etc.
Special LNBs have been developed for use in single-cable distribution systems. All four sub-bands of the Ku band (low frequency/horizontal polarity, high frequency/horizontal polarity, low frequency/vertical polarity, high frequency/vertical polarity) are received by a conventional front end, amplified and downconverted to the L-band, to be fed to a number of SatCR (Satellite Channel Router ...
The individual LNB's in the package may be standard (DC voltage selects polarisation) or stacked (both polarisations output at once, on different frequency). If the package contains a switch, it would either use 22 kHz to switch between two satellites (DirecTV, StarChoice) or use a proprietary switch (EchoStar/DishNetwork).
In an optical fibre system at the LNB the four sub-bands are "stacked" in frequency, one above the other, at 0.95 GHz-3.0 GHz (the whole frequency range received in vertical polarisation) and 3.4 GHz-5.45 GHz (horizontal polarisation) and transmitted together as a modulated optical signal down the fibre cable using a 1310 nm semiconductor laser.
In the box at the focus of the dish, called a low-noise block downconverter (LNB), each block of frequencies is converted to the IF range of 950–2150 MHz by two fixed frequency local oscillators at 9.75 and 10.6 GHz. One of the two blocks is selected by a control signal from the set top box inside, which switches on one of the local oscillators.