ODU (Out-Door Unit) refers to the set of satellite equipment which is placed outside of the building. The ODU typically includes a satellite dish, a feedhorn, and a LNB (Low Noise Block). In bi-directional satellite systems, the ODU will also include a BUC (Block Up Convertor). The ODU is connected to the IDU (In-Door-Unit) by the IFL (Inter-Facility-Link). The dish receives the signal and focuses it on the feedhorn. The feedhorn delivers the signal to the LNB. The LNB converts the satellite frequencies to an Intermediate Frequency (IF) which is Read More

A photoresistor is a light-dependent resistor which slowly loses its resistance when exposed to high levels of ultraviolet light. As a result, photoresistors convert light energy into electrical energy. Photoresistors are used in a wide variety of devices to detect the presence of light, control a device, or activate a system. They are usually dependent on external light sources, although they can be connected to a system that produces its own light. Photoresistors are generally made of cadmium sulfide but can be mixed with impurities to allow lower frequencies of light Read More

Geostationary satellites are located exactly above the earth’s equator and revolve around the earth in a circular orbit. Their revolving speed and direction (west to east) are exactly same as that of the earth, which makes it look stationary from the earth’s surface. The exact altitude of these satellites above the equator is approximately 36,000 Kilometers (22369 Miles). A geostationary satellite has to be at a set distance above the earth or it will suffer altitude decay. If it is too far from the Earth, it will escape the Earth’s gravitation Read More

A thermoelectric generator is a solid-state device that works similar to solar panels but converts heat, rather than sunlight, directly into electricity. A thermoelectric generator is usually made of bismuth telluride semiconductor junctions that are only several millimeters thick. This differs drastically from the bimetallic junctions that were previously used, which were much thicker. Thermoelectric generators generally do not have any moving parts, except for a fan, and can be used in a wide variety of applications to generate electricity. How Thermoelectric Generators Work In a thermoelectric generator, heat is Read More

A diode is a solid-state device that allows current to flow in only one direction, a process known as rectification. Diodes are a fundamental component of electrical circuits. They are also used to form other components, such as the bipolar transistor which uses two diodes in series. History of the Diode Thermionic rectifiers were discovered in 1873 by Frederick Guthrie, and later rediscovered by Thomas Edison in 1880, while crystal rectifiers were discovered in 1874 by Karl Braun. It wasn’t until 1919 that rectifiers were renamed diodes by William Eccles, Read More

Capacitive reactance is a term used to describe an effect in capacitors that causes the capacitor’s resistance to change depending on changes in the electric field passing through it. Capacitive reactance is similar to resistance in that it can allow or block varying amounts of voltage in a circuit, but is different because it is dependent on changes in frequency rather than changes in current. Capacitive reactance can be applied to various electronic devices, which include circuits that change frequency on a regular basis.   How Capacitive Reactance Works Like Read More

Crosstalk is a form of interference caused by signals in nearby conductors. The most common example is hearing an unwanted conversation on the telephone. Crosstalk can also occur in radios, televisions, networking equipment, and even electric guitars. Causes of Crosstalk Crosstalk is caused by coupling, the transfer of electrical energy between conductors. The three main types of coupling are capacitive, inductive, and conductive. Capacitive coupling occurs when two separate conductors are close enough together to act as a capacitor. Inductive coupling occurs when the current in one conductor induced a Read More

QPSK (Quadrature Phase Shift Keying) is a phase modulation algorithm. Phase modulation is a frequency modulation version where the carrier wave’s phase is modulated to encode bits of digital information in each phase change. The “PSK” in QPSK refers to the use of Phased Shift Keying. Phased Shift Keying is a form of phase modulation that is accomplished by using a discrete number of states. QPSK refers to PSK with 4 states. With half that number of states, there is a BPSK (Binary Phased Shift Keying). With twice the number Read More

A rectifier changes alternating current into direct current. This process is called rectification. The three main types of rectifier are the half-wave, full-wave, and bridge. A rectifier is the opposite of an inverter, which changes direct current into alternating current. Half-Wave Rectifier The simplest type is the half-wave rectifier, which can be made with just one diode. When the voltage of the alternating current is positive, the diode becomes forward-biased and current flows through it. When the voltage is negative, the diode is reverse-biased and the current stops. The result Read More

Low Earth Orbit (LEO) refers to a satellite which orbits the earth at altitudes between (very roughly) 200 miles and 930 miles. Low Earth Orbit satellites must travel very quickly to resist the pull of gravity — approximately 17,000 miles per hour. Because of this, Lowe Earth Orbit satellies can orbit the planet in as little as 90 minutes. Low Earth Orbit satellite systems require several dozen satellites to provide coverage of the entire planet. Low Earth Orbit satellites typically operate in polar orbits. Low Earth Orbit satellites are used Read More