Author Archives: Fairy

Digital Audio

Posted on November 21, 2011 by Fairy

Digital audio is sound reproduction using pulse-code modulation and digital signals. Digital audio systems include analog-to-digital conversion (ADC), digital-to-analog conversion (DAC), digital storage, processing and transmission components. A primary benefit of digital audio is in its convenience of storage, transmission … Continue reading →

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Microwave Communication Networks

Posted on November 18, 2011 by Fairy

A microwave link is a communications system that uses a beam of radio waves (> 1GHz) in the microwave frequency range to transmit information between two fixed locations on the earth. Microwaves are short-wavelength, high-frequency signals that occupy the electromagnetic … Continue reading →

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Feedhorn and LNB

Posted on November 17, 2011 by Fairy

The feedhorn is a device that collects the signals at the focus of the satellite dish and channels them to the LNB (Low Noise Block Down Converter). The LNB amplifies the received signals (3.6 – 4.2 GHz for C-band or … Continue reading →

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RF, IF and LO

Posted on November 17, 2011 by Fairy

RF is Radio Frequency that LNB can receive from a satellite. This would differ between a C-Band LNB, a Ku band standard LNB IF is Intermediate Frequency LO is local oscillating frequency The relationship between all these parameters are  RF … Continue reading →

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Satellite Loopback and a Terrestrial TX/RX loopback

Posted on November 17, 2011 by Fairy

IF loop: This command temporarily reconfigures the receive parameters to match the transmit parameters and internally connects IF out to IF in.  Useful to verify that the modem is OK. You don’t need to touch the external connectors. RF loop: … Continue reading →

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The demod does not lock in Satellite modem

Posted on November 17, 2011 by Fairy

Sometimes all of the settings look good on a modem, but it still does not lock. The frequency, data rate, and FEC are all correct, the signal shows up on the spectrum analyzer, and the cabling is good, but the … Continue reading →

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Upgrading firmware for Satellite Modem with Remote control

Posted on November 17, 2011 by Fairy

A good data connection really needs to be made on the DB-25 interface in order for the remote serial interface to work. In the uncommon case one needs to upgrade firmware, it is a simple process provided: You are using … Continue reading →

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Polarisation for Satellite Systems

Posted on November 16, 2011 by Fairy

The polarization of an electromagnetic wave is defined as the orientation of the electric field vector. It is perpendicular to both the direction of travel and the magnetic field vector. Satellite stations have to set as a same direction of … Continue reading →

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Frequency, Bandwidth and Data Rate

Posted on November 16, 2011 by Fairy

Frequency Frequency is a measure of the number of occurrences of a repeating event per unit time. Bandwidth In electronic communication, bandwidth is the width of the range (or band) of frequencies that an electronic signal uses on a given … Continue reading →

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Data Interfaces for Satellite Communication

Posted on November 16, 2011 by Fairy

RS-232 RS-232 is a very popular interface for low speed data signals. It is an unbalanced interface capable of operation from 0 to 20 KBPS at 50 feet. RS-232 is a voltage sensing interface, with the Mark (1) voltage being … Continue reading →

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