Satellite images were initially the exclusive realm of military and government agencies. They then became commercially available at very steep prices. Technology has now improved to the point where satellite images are available so inexpensively that they are now provided for free online. Free Satellite Images on the Web The best and by far the most popular source of web based free satellite images is Google Maps. This product can be directly used from the web browser. In addition to the pure satellite view, Google Maps lets users choose a Read More

Digital modulation is no new concept. Programmers and people working in today’s technological field know it for sure, as they have been using certain modulation techniques to transmit data digitally. However, several techniques are available for techies to choose from, and out of three popular digital modulation options, the PSK or Phase Shift Keying tops the list of the most valuable. PSK, as it is commonly known, works to modulate or adjust certain parts of the reference signal, which essentially is the carrier wave. This signal is changed in response Read More

A three way switch is a circuit commonly found in residential buildings and some businesses. They are used when multiple switches operate one or more lights at opposite ends of a large room, hallway, or staircase. Three way switches are similar to single pole switches, but have two connections on one side of the switch and one on the other, whereas a standard switch has two single connections. Three way switches have a “common” terminal, which usually has a different color from the other two, and is the lower screw Read More

Degaussing is a process of reducing the magnetism of a material by applying an opposite magnetic field. The name is derived from a unit of magnetic flux, the gauss. There are many different uses for degaussing. Cathode Ray Tubes Most televisions and computer monitors that use cathode ray tubes have a degaussing function. The electron beams cause a magnetic field to build up on the shadow mask, and this changes the path of the beams causing the picture to warp. An insulated bundle containing many turns of copper wire is Read More

A CMOS (Complementary Metal-oxide Semiconductor) inverter is a device that produces logic functions and is the primary component of all integrated circuits. A CMOS inverter is a field-effect transistor that is composed of a metal gate that lies on top of an insulating layer of oxygen, which lies on top of a semiconductor. CMOS inverters are found in most electronic devices and are responsible for producing data within small circuits. How CMOS Inverters Work CMOS inverters work like most other types of field-effect transistors, but depend on a layer of Read More

The military alphabet, or more properly the phonetic alphabet, exists in innumerable variants. If any military alphabet can be viewed as the most correct, it is the current NATO standard military alphabet. However, even with the NATO standard military alphabet, various member nations use numerous spelling variations. This version of the military alphabet is also known as the ICAO (International Civil Aviation Organization) code. The NATO Standard Military Alphabet This chart shows the current NATO standard military alphabet: Letter NATO A Alpha B Bravo C Charlie D Delta E Echo Read More

Intersymbol interference is a signal distortion in telecommunication. One or more symbols can interfere with other symbols causing noise or a less reliable signal. The main causes of intersymbol interference are multipath propagation or non-linear frequency in channels. This has the effect of a blur or mixture of symbols, which can reduce signal clarity. If intersymbol interference occurs within a system, the receiver output becomes erroneous at the decision device. This is an unfavorable result that should be reduced to the most minimal amount possible. Error rates from intersymbol interference Read More

The MMCX connector, or MicroMate, is a type of RF connector used with coaxial cables. Like its predecessor, the MCX connector, the MMCX connector is a very small connector, designed for the high frequency range. MMCX connectors can carry information in ranges up to 6 GHz, and were designed to meet the requirements set forth by the European CECC 22000 specification. Known as a type of micro-miniature connector, the MMCX connector is more flexible and more stable than the original MCX connector. It is currently the smallest connector available on Read More

The Federal Communications Commission (FCC) licenses the frequency spectrum in the United States. Useful charts showing frequency allocations are available from the National Telecommunications and Information Administration (NTIA) at http://www.ntia.doc.gov/osmhome/allochrt.html. This table shows commonly used names for various frequency ranges: Frequency Description 30 – 300 GHz Extremely High Frequency 3 – 30 GHz Super High Frequency 300 MHz – 3 GHz Ultra High Frequency (UHF) 30 – 300 MHz Very High Frequency (VHF) 3 – 30 MHz High Frequency (HF) 300 KHz – 3 MHz Medium Frequency 30 KHz – Read More

A gas-discharge tube uses electrodes inside a low-pressure gas to create light. When a high potential difference exists between the electrodes, the gas between them ionizes and forms a plasma. The free electrons in this plasma allows current to flow between the electrodes. The plasma either generates light directly, or by causing another material to create light. There are many different types such as the fluorescent, neon, xenon, sodium, metal halide, and switching tubes. Penning Mixture A pure gas has a much higher ionization voltage than a mixture of gases. Read More