Aviation refers to activities involving man-made flying devices (aircraft), including the people, organizations, and regulatory bodies involved ...
By the 1920s the first small commercial airlines had begun to carry mail, and the increased speed and range of aircraft made possible the first nonstop flights over the world’s oceans, poles, and continents. ...
Thursday, April 30, 2009
Definitions of Aviation
Tuesday, April 28, 2009
8086 Microprocessor
Intel 8086 microprocessor is a first member of x86 family of processors. Advertised as a "source-code compatible" with Intel 8080 and Intel 8085 processors, the 8086 was not object code compatible with them. The 8086 has complete 16-bit architecture - 16-bit internal registers, 16-bit data bus, and 20-bit address bus (1 MB of physical memory). Because the processor has 16-bit index registers and memory pointers, it can effectively address only 64 KB of memory. To address memory beyond 64 KB the CPU uses segment registers - these registers specify memory locations for code, stack, data and extra data 64 KB segments. The segments can be positioned anywhere in memory, and, if necessary, user programs can change their position. This addressing method has one big advantage - it is very easy to write memory-independent code when the size of code, stack and data is smaller than 64 KB each. The complexity of the code and programming increases, sometimes significantly, when the size of stack, data and/code is larger than 64 KB. To support different variations of this awkward memory addressing scheme many 8086 compilers included 6 different memory models: tiny, small, compact, medium, large and huge. 64 KB direct addressing limitation was eliminated with the introduction of the 32-bit protected mode in Intel 80386 processor.
Intel 8086 instruction set includes a few very powerful string instructions. When these instructions are prefixed by REP (repeat) instruction, the CPU will perform block operations - move block of data, compare data blocks, set data block to certain value, etc, that is one 8086 string instruction with a REP prefix could do as much as a 4-5 instruction loop on some other processors. To be fair, the Zilog Z80 included move and search block instructions, and Motorola 68000 could execute block operations using just two instructions.
The 8086 microprocessor provides support for Intel 8087 numeric co-processor. The CPU recognizes all Floating-Point (FP) instructions. When the FP instructions reference the memory, the CPU calculates memory address and performs dummy memory read. The calculated address, and possibly read data, is captured by the FPU. After that the CPU proceeds to the next instruction, while the FPU executes the floating-point instruction. Thus, both integer and floating-point instructions can be executed concurrently.
Original Intel 8086 CPU was manufactured using HMOS technology. Later Intel introduced 80C86 and 80C86A - CHMOS versions of the CPU. These microprocessors had much lower power consumption and featured standby mode.
Intel 8086 instruction set includes a few very powerful string instructions. When these instructions are prefixed by REP (repeat) instruction, the CPU will perform block operations - move block of data, compare data blocks, set data block to certain value, etc, that is one 8086 string instruction with a REP prefix could do as much as a 4-5 instruction loop on some other processors. To be fair, the Zilog Z80 included move and search block instructions, and Motorola 68000 could execute block operations using just two instructions.
The 8086 microprocessor provides support for Intel 8087 numeric co-processor. The CPU recognizes all Floating-Point (FP) instructions. When the FP instructions reference the memory, the CPU calculates memory address and performs dummy memory read. The calculated address, and possibly read data, is captured by the FPU. After that the CPU proceeds to the next instruction, while the FPU executes the floating-point instruction. Thus, both integer and floating-point instructions can be executed concurrently.
Original Intel 8086 CPU was manufactured using HMOS technology. Later Intel introduced 80C86 and 80C86A - CHMOS versions of the CPU. These microprocessors had much lower power consumption and featured standby mode.
8088 Microprocessor
Intel 8088 microprocessor was released in 1979, or one year after the Intel 8086 CPU. Both processors have the same architecture, and the only difference of the 8088 CPU from the 8086 is the external data bus width - it was reduced from 16 bits to 8 bits. The 8088 CPU uses two consecutive bus cycles to read or write 16 bit data instead of one bus cycle for the 8086, which makes the 8088 processor to run slower. On the plus side hardware changes to the 8088 CPU made it compatible with 8080/8085 support chips. This was an important factor in choosing the 8088 processor for IBM PC line of computers because at that time 8-bit support chips were cheaper than 16-bit support chips, and there was better selection of 8-bit chips.
The 8088 microprocessor has 16-bit registers, 16-bit internal data bus and 20-bit address bus, which allows the processor address up to 1 MB of memory. The 8088 uses the same segmented memory addressing as the 8086: the processor can address 64 KB of memory directly, and to address more than 64 KB of memory the CPU has to break the update into a few parts - update up to 64 KB of memory, change segment register, update another block of memory, update segment register again, and so on.
Like to 8086, the 8088 microprocessor supports Intel 8087 numeric co-processor. The CPU recognizes all Floating-Point (FP) instructions, and, when necessary, it calculates memory address for FP instruction operand and does a dummy memory read. The FPU captures the calculated address and, possibly, the data, and proceeds to execute FP instruction. The CPU at the same time starts executing the next instruction. Thus, both integer and floating-point instructions can be executed concurrently.
Original Intel 8088 microprocessor was manufactured using HMOS technology. There were also CHMOS versions of the chip - 80C88 and 80C88A. These microprocessors had much lower power consumption and featured standby mode.
The 8088 microprocessor has 16-bit registers, 16-bit internal data bus and 20-bit address bus, which allows the processor address up to 1 MB of memory. The 8088 uses the same segmented memory addressing as the 8086: the processor can address 64 KB of memory directly, and to address more than 64 KB of memory the CPU has to break the update into a few parts - update up to 64 KB of memory, change segment register, update another block of memory, update segment register again, and so on.
Like to 8086, the 8088 microprocessor supports Intel 8087 numeric co-processor. The CPU recognizes all Floating-Point (FP) instructions, and, when necessary, it calculates memory address for FP instruction operand and does a dummy memory read. The FPU captures the calculated address and, possibly, the data, and proceeds to execute FP instruction. The CPU at the same time starts executing the next instruction. Thus, both integer and floating-point instructions can be executed concurrently.
Original Intel 8088 microprocessor was manufactured using HMOS technology. There were also CHMOS versions of the chip - 80C88 and 80C88A. These microprocessors had much lower power consumption and featured standby mode.
The 8088 was the processor that fueled the personal computer revolution beginning with the IBM PC introduced in 1981. Squeezing 29,000 transistors onto a sliver of silicon using 3.0 micron technology, the Intel 8088 central processing unit (CPU) was produced in two versions: one with a clock speed of 5 MHz capable of 0.33 MIPS (millions of instructions per second) and the other at 8 MHz and 0.75 MIPS. With a 16-bit internal register width, this microprocessor was able to address 1 megabyte of memory.
Intel's first venture in 16-bit computing, the 8086, was not related to the previous silicon electronic devices (4004, 8008, 8080). It featured a new instruction set and different hardware architecture. As a clear case of the semiconductor engineers getting ahead of other hardware and software designers, and because of difficulties connecting to peripherals, the 8086 processor was largely left abandoned. The 8088 was the answer, internally an 8086 with a more versatile 8-bit external bus and marketed at a lower price. The 8088 was Intel's first really successful CPU because it was adopted by IBM for their PC and XT models and by most XT-class clones. Originally produced with simple, but energy-hungry N-channel metal oxide semiconductor (NMOS) technology, the 8086 and 8088 chips were produced by Intel in the more up-to-date complementary metal oxide semiconductor (CMOS) fabrication techniques as the low-voltage 80c86 and 80c88, respectively for the newly arrived battery-powered notebook and sub-notebook computers.
During its fledgling years, Intel had to have other, more established semiconductor manufacturers produce its chips like the 8088 since computer manufacturers such as IBM did not want to bet their entire personal computer line on an unproven entity. Japanese semiconductor pioneer NEC also made the 8088. They later tired of simply licensing rights and designs from Intel and reverse-engineered the processor to create the NEC V20. The V20 was more efficient than the 8088 (increased clock speed), while maintaining complete compatibility and using the same command set as the 8088 processor.
During its fledgling years, Intel had to have other, more established semiconductor manufacturers produce its chips like the 8088 since computer manufacturers such as IBM did not want to bet their entire personal computer line on an unproven entity. Japanese semiconductor pioneer NEC also made the 8088. They later tired of simply licensing rights and designs from Intel and reverse-engineered the processor to create the NEC V20. The V20 was more efficient than the 8088 (increased clock speed), while maintaining complete compatibility and using the same command set as the 8088 processor.
Microprocessor
A microprocessor incorporates most or all of the functions of a central processing unit (CPU) on a single integrated circuit (IC). [1] The first microprocessors emerged in the early 1970s and were used for electronic calculators, using Binary-coded decimal (BCD) arithmetic on 4-bit words. Other embedded uses of 4- and 8-bit microprocessors, such as terminals, printers, various kinds of automation etc, followed rather quickly. Affordable 8-bit microprocessors with 16-bit addressing also led to the first general purpose microcomputers in the mid-1970s.
Computer processors were for a long period constructed out of small and medium-scale ICs containing the equivalent of a few to a few hundred transistors. The integration of the whole CPU onto a single VLSI chip therefore greatly reduced the cost of processing capacity. From their humble beginnings, continued increases in microprocessor capacity have rendered other forms of computers almost completely obsolete (see history of computing hardware), with one or more microprocessor as processing element in everything from the smallest embedded systems and handheld devices to the largest mainframes and supercomputers.
Since the early 1970s, the increase in capacity of microprocessors has been known to generally follow Moore's Law, which suggests that the complexity of an integrated circuit, with respect to minimum component cost, doubles every two years.[2] In the late 1990s, and in the high performance microprocessor segment, heat generation (TDP), due to switching losses, static current leakage, and other factors, emerged as a leading developmental constraint[3].
Thursday, April 23, 2009
Electronics Sructures
The dual particle/wave nature of the electron has long been a paradox in physics. It is now seen that the electron consists entirely of a structure of spherical waves whose behavior creates their particle-like appearance. The correctness of this structure is supported by the physical laws which originate from this wave structure, including quantum theory, special relativity, electric force, gravity, and magnetism. This type of structure is termed a Space Resonance.
Modern Devices
A thorough examination of the present and future of semiconductor device technology
Engineers continue to develop new electronic semiconductor devices that are almost exponentially smaller, faster, and more efficient than their immediate predecessors. Theory of Modern Electronic Semiconductor Devices endeavors to provide an up-to-date, extended discussion of the most important emerging devices and trends in semiconductor technology, setting the pace for the next generation of the discipline's literature.
Kevin Brennan and April Brown focus on three increasingly important areas: telecommunications, quantum structures, and challenges and alternatives to CMOS technology. Specifically, the text examines the behavior of heterostructure devices for communications systems, quantum phenomena that appear in miniaturized structures and new nanoelectronic device types that exploit these effects, the challenges faced by continued miniaturization of CMOS devices, and futuristic alternatives. Device structures on the commercial and research levels analyzed in detail include:
* Heterostructure field effect transistors
* Bipolar and CMOS transistors
* Resonant tunneling diodes
* Real space transfer transistors
* Quantum dot cellular automata
* Single electron transistors
The book contains many homework exercises at the end of each chapter, and a solution manual can be obtained for instructors. Emphasizing the development of new technology, Theory of Modern Electronic Semiconductor Devices is an ideal companion to electrical and computer engineering graduate level courses and an essential reference for semiconductor device engineers.
Tuesday, April 21, 2009
Radar Invention
Radar is a system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain. The term RADAR was coined in 1941 as an acronym for radio detection and ranging.[1][2][3] The term has since entered the English language as a standard word, radar, losing the capitalization. Radar was originally called RDF (Radio Direction Finder, now used for a totally different device) in the United Kingdom.
A radar system has a transmitter that emits either microwaves or radio waves that are reflected by the target and detected by a receiver, typically in the same location as the transmitter. Although the signal returned is usually very weak, the signal can be amplified. This enables radar to detect objects at ranges where other emissions, such as sound or visible light, would be too weak to detect. Radar is used in many contexts, including meteorological detection of precipitation, measuring ocean surface waves, air traffic control, police detection of speeding traffic, and by the military.
Sunday, April 19, 2009
Radio
Etymology
Originally, radio or radiotelegraphy was called "wireless telegraphy", which was shortened to "wireless". The prefix radio- in the sense of wireless transmission, was first recorded in the word radio conductor, coined by the French physicist Édouard Branly in 1897 and based on the verb to radiate (in Latin "radius" means "spoke of a wheel, beam of light, ray"). "Radio" as a noun is said to have been coined by advertising expert Waldo Warren (White 1944). The word appears in a 1907 article by Lee De Forest, was adopted by the United States Navy in 1912 and became common by the time of the first commercial broadcasts in the United States in the 1920s. (The noun "broadcasting" itself came from an agricultural term, meaning "scattering seeds".) The term was then adopted by other languages in Europe and Asia, although British Commonwealth countries continued to use the term "wireless" until the mid-20th century.
In recent years the term "wireless" has gained renewed popularity through the rapid growth of short-range computer networking, e.g., Wireless Local Area Network (WLAN), WiFi and Bluetooth, as well as mobile telephony, e.g., GSM and UMTS. Today, the term "radio" often refers to the actual transceiver device or chip, whereas "wireless" refers to the system and/or method used for radio communication, hence one talks about radio transceivers and Radio Frequency Identification (RFID), but about wireless devices and wireless sensor networks.
[edit] Processes
Radio systems used for communications will have the following elements. With more than 100 years of development, each process is implemented by a wide range of methods, specialized for different communications purposes.
Each system contains a transmitter. This consists of a source of electrical energy, producing alternating current of a desired frequency of oscillation. The transmitter contains a system to modulate (change) some property of the energy produced to impress a signal on it. This modulation might be as simple as turning the energy on and off, or altering more subtle properties such as amplitude, frequency, phase, or combinations of these properties. The transmitter sends the modulated electrical energy to an antenna; this structure converts the rapidly-changing alternating current into an electromagnetic wave that can move through free space.
Electromagnetic waves travel through space either directly, or have their path altered by reflection, refraction or diffraction. The intensity of the waves diminishes due to geometric dispersion (the inverse-square law); some energy may also be absorbed by the intervening medium in some cases. Noise will generally alter the desired signal; this electromagnetic interference comes from natural sources, as well as from artificial sources such as other transmitters and accidental radiators. Noise is also produced at every step due to the inherent properties of the devices used. If the magnitude of the noise is large enough, the desired signal will no longer be discernible; this is the fundamental limit to the range of radio communications.
The electromagnetic wave is intercepted by a receiving antenna; this structure captures some of the energy of the wave and returns it to the form of oscillating electrical currents. At the receiver, these currents are demodulated, which is conversion to a usable signal form by a detector sub-system. The receiver is "tuned" to respond preferentially to the desired signals, and reject undesired signals.
Early radio systems relied entirely on the energy collected by an antenna to produce signals for the operator. Radio became more useful after the invention of electronic devices such as the vacuum tube and later the transistor, which made it possible to amplify weak signals. Today radio systems are used for applications from walkie-talkie children's toys to the control of space vehicles, as well as for broadcasting, and many other applications.
[edit] History
Main article: History of radio
[edit] Invention
Main article: Invention of radio
The meaning and usage of the word "radio" has developed in parallel with developments within the field and can be seen to have three distinct phases: electromagnetic waves and experimentation; wireless communication and technical development; and radio broadcasting and commercialization. Many individuals -- inventors, engineers, developers, businessmen -- contributed to produce the modern idea of radio and thus the origins and 'invention' are multiple and controversial.
Development from a laboratory demonstration to commercial utility spanned several decades and required the efforts of many practitioners. Thomas Edison applied in 1885 to the U.S. Patent Office for a patent on a wireless telegraphy system which anticipated later developments in the field. The patent was granted as Patent # 465971 on December 29, 1891, and Guglielmo Marconi felt it necessary to purchase rights to the Edison wireless telegraphy patent as a foundation stone of his own subsequent work in wireless telegraphy.
Tesla demonstrating wireless transmissions during his high frequency and potential lecture of 1891. After continued research, Tesla presented the fundamentals of radio in 1893.
In 1893, in St. Louis, Missouri, Nikola Tesla made devices for his experiments with electricity. Addressing the Franklin Institute in Philadelphia and the National Electric Light Association, he described and demonstrated in detail the principles of his wireless work.[1] The descriptions contained all the elements that were later incorporated into radio systems before the development of the vacuum tube. He initially experimented with magnetic receivers, unlike the coherers (detecting devices consisting of tubes filled with iron filings which had been invented by Temistocle Calzecchi-Onesti at Fermo in Italy in 1884) used by Guglielmo Marconi and other early experimenters.[2]
The first radio couldn't transmit sound or speech and was called the "wireless telegraph." The first public demonstration of wireless telegraphy took place in the lecture theater of the Oxford University Museum of Natural History on August 14, 1894, carried out by Professor Oliver Lodge and Alexander Muirhead. During the demonstration a radio signal was sent from the neighboring Clarendon laboratory building, and received by apparatus in the lecture theater.
In 1895 Alexander Stepanovich Popov built his first radio receiver, which contained a coherer. Further refined as a lightning detector, it was presented to the Russian Physical and Chemical Society on May 7, 1895. A depiction of Popov's lightning detector was printed in the Journal of the Russian Physical and Chemical Society the same year. Popov's receiver was created on the improved basis of Lodge's receiver, and originally intended for reproduction of its experiments.
[edit] Development
Telephone Herald in Budapest, Hungary (1901).
In 1896, Marconi was awarded the British patent 12039, Improvements in transmitting electrical impulses and signals and in apparatus there-for, for radio. In 1897 he established the world's first radio station on the Isle of Wight, England. Marconi opened the world's first "wireless" factory in Hall Street, Chelmsford, England in 1898, employing around 50 people.
The next great invention was the vacuum tube detector, invented by Westinghouse engineers. On Christmas Eve, 1906, Reginald Fessenden used a synchronous rotary-spark transmitter for the first radio program broadcast, from Ocean Bluff-Brant Rock, Massachusetts. Ships at sea heard a broadcast that included Fessenden playing O Holy Night on the violin and reading a passage from the Bible. This was, for all intents and purposes, the first transmission of what is now known as amplitude modulation or AM radio. The first radio news program was broadcast August 31, 1920 by station 8MK in Detroit, Michigan, which survives today as all-news format station WWJ under ownership of the CBS network. The first college radio station began broadcasting on October 14, 1920, from Union College, Schenectady, New York under the personal call letters of Wendell King, an African-American student at the school.[3] That month 2ADD, later renamed WRUC in 1940, aired what is believed to be the first public entertainment broadcast in the United States, a series of Thursday night concerts initially heard within a 100-mile (160 km) radius and later for a 1,000-mile (1,600 km) radius. In November 1920, it aired the first broadcast of a sporting event.[3][4] At 9 pm on August 27, 1920, Sociedad Radio Argentina aired a live performance of Richard Wagner's Parsifal opera from the Coliseo Theater in downtown Buenos Aires, only about twenty homes in the city had a receiver to tune in. Meanwhile, regular entertainment broadcasts commenced in 1922 from the Marconi Research Centre at Writtle, England.
American girl listens to radio during the Great Depression.
One of the first developments in the early 20th century (1900-1959) was that aircraft used commercial AM radio stations for navigation. This continued until the early 1960s when VOR systems finally became widespread (though AM stations are still marked on U.S. aviation charts). In the early 1930s, single sideband and frequency modulation were invented by amateur radio operators. By the end of the decade, they were established commercial modes. Radio was used to transmit pictures visible as television as early as the 1920s. Commercial television transmissions started in North America and Europe in the 1940s. In 1954, Regency introduced a pocket transistor radio, the TR-1, powered by a "standard 22.5 V Battery".
In 1960, Sony introduced its first transistorized radio, small enough to fit in a vest pocket, and able to be powered by a small battery. It was durable, because there were no tubes to burn out. Over the next 20 years, transistors replaced tubes almost completely except for very high-power uses. By 1963 color television was being regularly transmitted commercially, and the first (radio) communication satellite, Telstar, was launched. In the late 1960s, the U.S. long-distance telephone network began to convert to a digital network, employing digital radios for many of its links. In the 1970s, LORAN became the premier radio navigation system. Soon, the U.S. Navy experimented with satellite navigation, culminating in the invention and launch of the GPS constellation in 1987. In the early 1990s, amateur radio experimenters began to use personal computers with audio cards to process radio signals. In 1994, the U.S. Army and DARPA launched an aggressive, successful project to construct a software-defined radio that can be programmed to be virtually any radio by changing its software program. Digital transmissions began to be applied to broadcasting in the late 1990s.
[edit] Uses of radio
Early uses were maritime, for sending telegraphic messages using Morse code between ships and land. The earliest users included the Japanese Navy scouting the Russian fleet during the Battle of Tsushima in 1905. One of the most memorable uses of marine telegraphy was during the sinking of the RMS Titanic in 1912, including communications between operators on the sinking ship and nearby vessels, and communications to shore stations listing the survivors.
Radio was used to pass on orders and communications between armies and navies on both sides in World War I; Germany used radio communications for diplomatic messages once it discovered that its submarine cables had been tapped by the British. The United States passed on President Woodrow Wilson's Fourteen Points to Germany via radio during the war. Broadcasting began from San Jose in 1909[5], and became feasible in the 1920s, with the widespread introduction of radio receivers, particularly in Europe and the United States. Besides broadcasting, point-to-point broadcasting, including telephone messages and relays of radio programs, became widespread in the 1920s and 1930s. Another use of radio in the pre-war years was the development of detection and locating of aircraft and ships by the use of radar (RAdio Detection And Ranging).
Today, radio takes many forms, including wireless networks and mobile communications of all types, as well as radio broadcasting. Before the advent of television, commercial radio broadcasts included not only news and music, but dramas, comedies, variety shows, and many other forms of entertainment. Radio was unique among methods of dramatic presentation in that it used only sound. For more, see radio programming.
[edit] Audio
A Fisher 500 AM/FM hi-fi receiver from 1959.
AM broadcast radio sends music and voice in the Medium Frequency (MF, 0.3 MHz to 3 MHz) radio spectrum. AM radio uses amplitude modulation, in which the amplitude of the transmitted signal is made proportional to the sound amplitude captured (transduced) by the microphone, while the transmitted frequency remains unchanged. Transmissions are affected by static and interference because lightning and other sources of radio emissions on the same frequency add their amplitudes to the original transmitted amplitude. In the early part of the 20th century, American AM radio stations broadcast with powers as high as 500 kW, and some could be heard worldwide; these stations' transmitters were commandeered for military use by the US Government during World War II. Currently, the maximum broadcast power for a civilian AM radio station in the United States and Canada is 50 kW, and the majority of stations that emit signals this powerful were grandfathered in; these include WGN (AM), WJR, KGA at 50 kW. In 1986 KTNN received the last granted 50,000 watt license. These 50 kW stations are generally called "clear channel" stations (Not to be confused with the Clear Channel radio conglomerate), because within North America each of these stations has exclusive use of its broadcast frequency throughout part or all of the broadcast day.
Bush House, home of the BBC World Service.
FM broadcast radio sends music and voice with higher fidelity than AM radio. In frequency modulation, amplitude variation at the microphone causes the transmitter frequency to fluctuate. Because the audio signal modulates the frequency and not the amplitude, an FM signal is not subject to static and interference in the same way as AM signals. Due to its need for a wider bandwidth, FM is transmitted in the Very High Frequency (VHF, 30 MHz to 300 MHz) radio spectrum. VHF radio waves act more like light, traveling in straight lines, hence the reception range is generally limited to about 50-100 miles. During unusual upper atmospheric conditions, FM signals are occasionally reflected back towards the Earth by the ionosphere, resulting in Long distance FM reception. FM receivers are subject to the capture effect, which causes the radio to only receive the strongest signal when multiple signals appear on the same frequency. FM receivers are relatively immune to lightning and spark interference.
High power is useful in penetrating buildings, diffracting around hills, and refracting for some distance beyond the horizon. Consequently, 100,000 watt FM stations can regularly be heard up to 100 miles (160 km) away, and farther (e.g., 150 miles, 240 km) if there are no competing signals. A few old, "grandfathered" stations do not conform to these power rules. WBCT-FM (93.7) in Grand Rapids, Michigan, USA, runs 320,000 watts ERP, and can increase to 500,000 watts ERP by the terms of its original license. Such a huge power level does not usually help to increase range as much as one might expect, because VHF frequencies travel in nearly straight lines over the horizon and off into space. Nevertheless, when there were fewer FM stations competing, this station could be heard near Bloomington, Illinois, USA, almost 300 miles (500 km) away.[citation needed]
Pure One Classic- DAB Digital Radio from 2008
FM subcarrier services are secondary signals transmitted in a "piggyback" fashion along with the main program. Special receivers are required to utilize these services. Analog channels may contain alternative programming, such as reading services for the blind, background music or stereo sound signals. In some extremely crowded metropolitan areas, the sub-channel program might be an alternate foreign language radio program for various ethnic groups. Sub-carriers can also transmit digital data, such as station identification, the current song's name, web addresses, or stock quotes. In some countries, FM radios automatically re-tune themselves to the same channel in a different district by using sub-bands.
Aviation voice radios use VHF AM. AM is used so that multiple stations on the same channel can be received. (Use of FM would result in stronger stations blocking out reception of weaker stations due to FM's capture effect). Aircraft fly high enough that their transmitters can be received hundreds of miles (or kilometres) away, even though they are using VHF.
Marine voice radios can use single sideband voice (SSB) in the shortwave High Frequency (HF—3 MHz to 30 MHz) radio spectrum for very long ranges or narrowband FM in the VHF spectrum for much shorter ranges. Narrowband FM sacrifices fidelity to make more channels available within the radio spectrum, by using a smaller range of radio frequencies, usually with five kHz of deviation, versus the 75 kHz used by commercial FM broadcasts, and 25 kHz used for TV sound.
Government, police, fire and commercial voice services also use narrowband FM on special frequencies. Early police radios used AM receivers to receive one-way dispatches.
Civil and military HF (high frequency) voice services use shortwave radio to contact ships at sea, aircraft and isolated settlements. Most use single sideband voice (SSB), which uses less bandwidth than AM. On an AM radio SSB sounds like ducks quacking. Viewed as a graph of frequency versus power, an AM signal shows power where the frequencies of the voice add and subtract with the main radio frequency. SSB cuts the bandwidth in half by suppressing the carrier and (usually) lower sideband. This also makes the transmitter about three times more powerful, because it doesn't need to transmit the unused carrier and sideband.
TETRA, Terrestrial Trunked Radio is a digital cell phone system for military, police and ambulances. Commercial services such as XM, WorldSpace and Sirius offer encrypted digital Satellite radio.
[edit] Telephony
Mobile phones transmit to a local cell site (transmitter/receiver) that ultimately connects to the public switched telephone network (PSTN) through an optic fiber or microwave radio and other network elements. When the mobile phone nears the edge of the cell site's radio coverage area, the central computer switches the phone to a new cell. Cell phones originally used FM, but now most use various digital modulation schemes. Recent developments in Sweden (such as DROPme) allow for the instant downloading of digital material from a radio broadcast (such as a song) to a mobile phone.
Satellite phones use satellites rather than cell towers to communicate.
[edit] Video
Television sends the picture as AM and the sound as FM, with the sound carrier a fixed frequency (4.5 MHz in the NTSC system) away from the video carrier. Analog television also uses a vestigial sideband on the video carrier to reduce the bandwidth required.
Digital television uses 8VSB modulation in North America (under the ATSC digital television standard), and COFDM modulation elsewhere in the world (using the DVB-T standard). A Reed–Solomon error correction code adds redundant correction codes and allows reliable reception during moderate data loss. Although many current and future codecs can be sent in the MPEG-2 transport stream container format, as of 2006 most systems use a standard-definition format almost identical to DVD: MPEG-2 video in Anamorphic widescreen and MPEG layer 2 (MP2) audio. High-definition television is possible simply by using a higher-resolution picture, but H.264/AVC is being considered as a replacement video codec in some regions for its improved compression. With the compression and improved modulation involved, a single "channel" can contain a high-definition program and several standard-definition programs.
[edit] Navigation
All satellite navigation systems use satellites with precision clocks. The satellite transmits its position, and the time of the transmission. The receiver listens to four satellites, and can figure its position as being on a line that is tangent to a spherical shell around each satellite, determined by the time-of-flight of the radio signals from the satellite. A computer in the receiver does the math.
Radio direction-finding is the oldest form of radio navigation. Before 1960 navigators used movable loop antennas to locate commercial AM stations near cities. In some cases they used marine radiolocation beacons, which share a range of frequencies just above AM radio with amateur radio operators. LORAN systems also used time-of-flight radio signals, but from radio stations on the ground. VOR (Very High Frequency Omnidirectional Range), systems (used by aircraft), have an antenna array that transmits two signals simultaneously. A directional signal rotates like a lighthouse at a fixed rate. When the directional signal is facing north, an omnidirectional signal pulses. By measuring the difference in phase of these two signals, an aircraft can determine its bearing or radial from the station, thus establishing a line of position. An aircraft can get readings from two VORs and locate its position at the intersection of the two radials, known as a "fix." When the VOR station is collocated with DME (Distance Measuring Equipment), the aircraft can determine its bearing and range from the station, thus providing a fix from only one ground station. Such stations are called VOR/DMEs. The military operates a similar system of navaids, called TACANs, which are often built into VOR stations. Such stations are called VORTACs. Because TACANs include distance measuring equipment, VOR/DME and VORTAC stations are identical in navigation potential to civil aircraft.
[edit] Radar
Radar (Radio Detection And Ranging) detects objects at a distance by bouncing radio waves off them. The delay caused by the echo measures the distance. The direction of the beam determines the direction of the reflection. The polarization and frequency of the return can sense the type of surface. Navigational radars scan a wide area two to four times per minute. They use very short waves that reflect from earth and stone. They are common on commercial ships and long-distance commercial aircraft.
General purpose radars generally use navigational radar frequencies, but modulate and polarize the pulse so the receiver can determine the type of surface of the reflector. The best general-purpose radars distinguish the rain of heavy storms, as well as land and vehicles. Some can superimpose sonar data and map data from GPS position.
Search radars scan a wide area with pulses of short radio waves. They usually scan the area two to four times a minute. Sometimes search radars use the Doppler Effect to separate moving vehicles from clutter. Targeting radars use the same principle as search radar but scan a much smaller area far more often, usually several times a second or more. Weather radars resemble search radars, but use radio waves with circular polarization and a wavelength to reflect from water droplets. Some weather radar use the Doppler Effect to measure wind speeds.
[edit] Data (digital radio)
Most new radio systems are digital, see also: Digital TV, Satellite Radio, Digital Audio Broadcasting. The oldest form of digital broadcast was spark gap telegraphy, used by pioneers such as Marconi. By pressing the key, the operator could send messages in Morse code by energizing a rotating commutating spark gap. The rotating commutator produced a tone in the receiver, where a simple spark gap would produce a hiss, indistinguishable from static. Spark gap transmitters are now illegal, because their transmissions span several hundred megahertz. This is very wasteful of both radio frequencies and power.
The next advance was continuous wave telegraphy, or CW (Continuous Wave), in which a pure radio frequency, produced by a vacuum tube electronic oscillator was switched on and off by a key. A receiver with a local oscillator would "heterodyne" with the pure radio frequency, creating a whistle-like audio tone. CW uses less than 100 Hz of bandwidth. CW is still used, these days primarily by amateur radio operators (hams). Strictly, on-off keying of a carrier should be known as "Interrupted Continuous Wave" or ICW or on-off keying (OOK).
Radio teletypes usually operate on short-wave (HF) and are much loved by the military because they create written information without a skilled operator. They send a bit as one of two tones. Groups of five or seven bits become a character printed by a teletype. From about 1925 to 1975, radio teletype was how most commercial messages were sent to less developed countries. These are still used by the military and weather services.
Aircraft use a 1200 Baud radioteletype service over VHF to send their ID, altitude and position, and get gate and connecting-flight data. Microwave dishes on satellites, telephone exchanges and TV stations usually use quadrature amplitude modulation (QAM). QAM sends data by changing both the phase and the amplitude of the radio signal. Engineers like QAM because it packs the most bits into a radio signal when given an exclusive (non-shared) fixed narrowband frequency range. Usually the bits are sent in "frames" that repeat. A special bit pattern is used to locate the beginning of a frame.
Modern GPS receivers.
Communication systems that limit themselves to a fixed narrowband frequency range are vulnerable to jamming. A variety of jamming-resistant spread spectrum techniques were initially developed for military use, most famously for Global Positioning System satellite transmissions. Commercial use of spread spectrum began in the 1980s. Bluetooth, most cell phones, and the 802.11b version of Wi-Fi each use various forms of spread spectrum.
Systems that need reliability, or that share their frequency with other services, may use "coded orthogonal frequency-division multiplexing" or COFDM. COFDM breaks a digital signal into as many as several hundred slower subchannels. The digital signal is often sent as QAM on the subchannels. Modern COFDM systems use a small computer to make and decode the signal with digital signal processing, which is more flexible and far less expensive than older systems that implemented separate electronic channels. COFDM resists fading and ghosting because the narrow-channel QAM signals can be sent slowly. An adaptive system, or one that sends error-correction codes can also resist interference, because most interference can affect only a few of the QAM channels. COFDM is used for Wi-Fi, some cell phones, Digital Radio Mondiale, Eureka 147, and many other local area network, digital TV and radio standards.
[edit] Heating
Radio-frequency energy generated for heating of objects is generally not intended to radiate outside of the generating equipment, to prevent interference with other radio signals. Microwave ovens use intense radio waves to heat food. Diathermy equipment is used in surgery for sealing of blood vessels. Induction furnaces are used for melting metal for casting.
[edit] Amateur radio service
Amateur radio station with multiple receivers and transceivers
Amateur radio, also known as "ham radio", is a hobby in which enthusiasts are licensed to communicate on a number of bands in the radio frequency spectrum non-commercially and for their own enjoyment. They may also provide emergency and public service assistance. This has been very beneficial in emergencies, saving lives in many instances.[6] Radio amateurs use a variety of modes, including nostalgic ones like morse code and experimental ones like Low-Frequency Experimental Radio. Several forms of radio were pioneered by radio amateurs and later became commercially important including FM, single-sideband (SSB), AM, digital packet radio and satellite repeaters. Some amateur frequencies may be disrupted by power-line internet service.
[edit] Unlicensed radio services
Unlicensed, government-authorized personal radio services such as Citizens' band radio in Australia, the USA, and Europe, and Family Radio Service and Multi-Use Radio Service in North America exist to provide simple, (usually) short range communication for individuals and small groups, without the overhead of licensing. Similar services exist in other parts of the world. These radio services involve the use of handheld units.
Free radio stations, sometimes called pirate radio or "clandestine" stations, are unauthorized, unlicensed, illegal broadcasting stations. These are often low power transmitters operated on sporadic schedules by hobbyists, community activists, or political and cultural dissidents. Some pirate stations operating offshore in parts of Europe and the United Kingdom more closely resembled legal stations, maintaining regular schedules, using high power, and selling commercial advertising time.[7] [8]
[edit] Radio control (RC)
Radio remote controls use radio waves to transmit control data to a remote object as in some early forms of guided missile, some early TV remotes and a range of model boats, cars and airplanes. Large industrial remote-controlled equipment such as cranes and switching locomotives now usually use digital radio techniques to ensure safety and reliability.
In Madison Square Garden, at the Electrical Exhibition of 1898, Nikola Tesla successfully demonstrated a radio-controlled boat.[9] He was awarded U.S. patent No. 613,809 for a "Method of and Apparatus for Controlling Mechanism of Moving Vessels or Vehicles."[10]
Television
Television (TV) is a widely used telecommunication medium for transmitting and receiving moving images, either monochromatic ("black and white") or color, usually accompanied by sound. "Television" may also refer specifically to a television set, television programming or television transmission. The word is derived from mixed Latin and Greek roots, meaning "far sight": Greek tele (τῆλε), far, and Latin visio, sight (from video, vis- to see, or to view in the first person).
Commercially available since the late 1930s, the television set has become a common communications receiver in homes, businesses and institutions, particularly as a source of entertainment and news. Since the 1970s the availability of video cassettes, laserdiscs, DVDs and now Blu-ray discs, have resulted in the television set frequently being used for viewing recorded as well as broadcast material.
A standard television set comprises multiple internal electronic circuits, including those for tuning and decoding broadcast signals. A display device which lacks a tuner is properly called a monitor, rather than a television. A television system may use different technical standards such as digital television (DTV) and high-definition television (HDTV). Television systems are also used for surveillance, industrial process control, and guiding of weapons, in places where direct observation is difficult or dangerous.
Amateur television (HAM TV or ATV) is also used for experimentation, pleasure and public service events by amateur radio operators. HAM TV stations were on the air in many cities before commercial TV stations came on the air - see http://www.earlytelevision.org/1940_home_camera.html for more info.
In its early stages of development, television included only those devices employing a combination of optical, mechanical and electronic technologies to capture, transmit and display a visual image. By the late 1920s, however, those employing only optical and electronic technologies were being explored. All modern television systems rely on the latter, however the knowledge gained from the work on mechanical-dependent systems was crucial in the development of fully electronic television.
The first time images were transmitted electrically were via early mechanical fax machines, including the pantelegraph. The concept of electrically-powered transmission of television images in motion, was first sketched in 1878 as the telephonoscope, shortly after the invention of the telephone. At the time, it was imagined by early science fiction authors, that someday that light could be transmitted over wires, as sounds were.[citation needed]
The idea of using scanning to transmit images was put to actual practical use in 1881 in the pantelegraph, through the use of a pendulum-based scanning mechanism. From this period forward, scanning in one form or another, has been used in nearly every image transmission technology to date, including television. This is the concept of "rasterization", the process of converting a visual image into a stream of electrical pulses.[citation needed]
In 1884 Paul Gottlieb Nipkow, a 20-year old university student in Germany, patented the first electromechanical television system which employed a scanning disk, a spinning disk with a series of holes spiraling toward the center, for rasterization. The holes were spaced at equal angular intervals such that in a single rotation the disk would allow light to pass through each hole and onto a light-sensitive selenium sensor which produced the electrical pulses. As an image was focused on the rotating disk, each hole captured a horizontal "slice" of the whole image, in a scanning fashion.[citation needed]
Nipkow's design would not be practical until advances in amplifier tube technology became available in 1907. Even then the device was only useful for transmitting still "halftone" images - represented by equally spaced dots of varying size - over telegraph or telephone lines. Later designs would use a rotating mirror-drum scanner to capture the image and a cathode ray tube (CRT) as a display device, but moving images were still not possible, due to the poor sensitivity of the selenium sensors.[citation needed]
Scottish inventor John Logie Baird demonstrated the transmission of moving silhouette images in London in 1925, and of moving, monochromatic images in 1926. Baird's scanning disk produced an image of 30 lines resolution, barely enough to discern a human face, from a double spiral of lenses.[citation needed]
In 1926, Hungarian engineer Kálmán Tihanyi invented the entirely electronic camera tube and entirely electronic display and the transmitting and receiving system.[2][3][4][5]
By 1927, Russian inventor Léon Theremin developed a mirror drum-based television system which used interlacing to achieve an image resolution of 100 lines.[citation needed]
Also in 1927, Herbert E. Ives of Bell Labs transmitted moving images from a 50-aperture disk producing 16 frames per minute over a cable from Washington, DC to New York City, and via radio from Whippany, New Jersey. Ives used viewing screens as large as 24 by 30 inches (60 by 75 centimeters). His subjects included Secretary of Commerce Herbert Hoover.[citation needed]
In 1928, Philo Farnsworth made the world's first working television system with electronic scanning of both the pickup and display devices, which he first demonstrated to news media on 1 September 1928, televising a motion picture film.[citation needed]
In 1936, Kálmán Tihanyi described the principle of Plasma Television, the first flat panel. [6][7]
Programming
Getting TV programming shown to the public can happen in many different ways. After production the next step is to market and deliver the product to whatever markets are open to using it. This typically happens on two levels:
- Original Run or First Run – a producer creates a program of one or multiple episodes and shows it on a station or network which has either paid for the production itself or to which a license has been granted by the producers to do the same.
- Syndication – this is the terminology rather broadly used to describe secondary programming usages (beyond original run). It includes secondary runs in the country of first issue, but also international usage which may or may not be managed by the originating producer. In many cases other companies, TV stations or individuals are engaged to do the syndication work, in other words to sell the product into the markets they are allowed to sell into by contract from the copyright holders, in most cases the producers.
First run programming is increasing on subscription services outside the U.S., but few domestically produced programs are syndicated on domestic FTA elsewhere. This practice is increasing however, generally on digital-only FTA channels, or with subscriber-only first run material appearing on FTA.
Unlike the U.S., repeat FTA screenings of a FTA network program almost only occur on that network. Also, Affiliates rarely buy or produce non-network programming that is not centred around local events.
Friday, April 10, 2009
Infrared gate
This is an infrared gate with two sensors planned to use in the wall in the way behind a door. It can be applied in a toilet to keep track of that someone is inside exceeding a certain amount of time. After that time elapsed, the circuit triggers the digital output wich can turn on a ventillator. The time period the output is turned on can be separately controlled by a second timer.
If you plan to build this circuit, beware that you may have lots of difficulties though the schematic may seem simple. The construction of the circit requires some amount of equipment like an oscilloscope and a DVM, too. Without them, the device will do weird things you wouldn't expect, and even if it is correctly put together, you must adjust it with care both mechanically in its final place and electronically with the help of an oscilloscope. Only if you want to span about less than 20-30 inches with the infra diodes can forget about this calibration. Alternatively you can take ideas from this construction.
Schematics
The device consists of several parts, the most critical one is the panel with the infra LEDs. I tried to use several receiver transistors, but best result was given by infra receiver diodes used in TV remote control receivers. The receiver diodes must be properly shielded from the transmitter LED(s) otherwise the infra light will surely drive the receiver with a large enough signal. These photodiodes should only see infrared light coming from the mirror. The two very sensitive receiver parts should also be isolated from the transmitter electrically or the TX signal will get across the wires to the RX lines, which results the same effect as weak optical shielding. Use metal shielding around the receiver amplifiers where possible. The infrared transmitter LEDs should be close in wavelength to the max. sensitivity band of the receivers. You can experiment with using more LEDs and more current testing several resistor values, but don't exceed the 500 mA current limit flowing on the diodes or they will burn out. Do not shield the transmitters, allow the maximum amount of infralight to reach the mirror to extend the possible range.
It is also important to protect the receiver diodes from direct light as natural light will weaken the sensitivity of the diodes, and lamps will transform the 50/60 Hz modulation present in the line power. Small noise is not problem, but the received signal from the TX generator should be stronger to be able to detect it. After the ST adjustments, connect LEDs to the 74123's TTL outputs through proper value resistors. The 74123 here is used as a demodulator. If there is a periodic signal change on the input, the output will be high, while if there is no activity on the input for a given period of time, the output falls low. When you cover the line of sight of one receiver diode, the corresponding LED turns off. There should not be any flickering in the turning on/off, the output should immediately respond to the change without blinking.
If still everything is correctly working at this point, the remaining digital circuit is the easy part of the work. The outputs of the previous circuit (LEFT, RIGHT) directly connect to the remaining part. The RS memory built from two NAND gates remembers the way of the last movement direction, so if someone is in or not. If you experience problems, connect another LED to pin 10 of the RS and check if this part does what it should. If there was any activity in the past minutes, the first timer is running, but it can only trigger the second timer part, if someone is still inside. The diode from the second timer output prevents resetting itself before the timing period is over in case of another movement. For a 1 minute timing (first timer) R=470k C=100u can be used, the second part would use R=1.5M C=470u for about a 15 minute timing (t=1.1RC). The output of the second timer (pin 9) can drive a relay activating the ventillator.
INTRODUCTION TO AMPLIFIER DESIGN
"An amplifier, with or without negative feedback, having the greatest fidelity in faithfully reproducing the input with the least distortion. It is however the least efficient, in as much the power delivered to the load is only a small percentage of the d.c. power used up in the amplification process.
REGULATION OF VOLTAGES
To regulate small amounts of current the cheapest approach is to use a zener diode. Higher currents can be obtained from higher power zeners but I prefer to use dedicated I.C.'s in these cases. In one instance you can use a zener diode in conjunction with a pass transistor to extend the range of the zener regulator.
As with our previous design example in Part - 1 we had a small unregulated bench supply of 500 ma for our projects. Now we have decided that it should become a well regulated, well filtered supply giving us 13V dc.
By using a series pass transistor we are extending the useful range of the zener diode as well as reducing Vo ripple. This is called "electronic filtering".
There is one large handicap with this circuit though. Under over-current conditions Q1 will most likely be destroyed long before F1 blows. Of course I have very cynical (practical?) friends who will tell you that if you buy up Q1 types at 5c each then in fact they are cheaper than most fuses anyway. Q1 usually requires a suitable heatsink.
FACT: Back in the olden days when transistors first emerged (and were incredibly expensive believe me) valve enthusiasts, (code for non-transistor literate) described transistors as "the dearest, but fastest acting fuse so far devised by man."
Most calculations you will note are still in accordance with the example in Part 1.
To calculate the value of Rs in the above figure you need to know the base current Ibfor Q1. This is the emitter current Ie divided by the transistor beta. It is preferable to meaure the transistor beta if you can (some meters have this facility) because the spread of beta on most transistors, even from the same batch, is about as wide as Sydney Harbour.
For the purposes of this exercise we will use the general purpose but cheap 2N3055 which will be mounted on a heat sink. Our beta measured 34. (if in doubt use mfrs. minimum beta from data sheet). Our base current is the emitter current divided by beta.
In this case we have 500ma/34 or 14.7ma. Also for decent regulation ZD1 needs a fair amount of current. I would suggest something about 25ma. Armed with this information, if Iz = 25ma minus the earlier Ib of 14.7ma = 10.3ma and if our dc voltage at C1 is 25.3V and our zener is 14V then Rs = [25.3V - 14V]/0.0103 = 1097 . I would use 1K
The power rating of both the zener and Rs are calculated as follows:
ZENER Pd = [ ( Vin - Vz) / Rs] X Vz = [ ( 25.3 - 14) / 1000 ] X 14 = 0.16W
It is quite common to use a safety factor of 5 so I would opt for a 1W type zener.
Rs Pd = ( Vin max - Vz )2 / Rs = ( 25.3 - 14 )2 / 1000 = 0.128W (use a 1/2 watt resistor).
CURRENT LIMITING - I have decided it is pointless including design for additional circuits for current limiting as this is provided even more economically with dedicated IC's. In fact all of the foregoing is mainly to give you the general basics.
NEXT - Part 3 - Even better Regulated Voltages and higher power output.
AM/FM Radio Project Kit
AM/FM radio kit and training course contains 14 transistors and 5 diodes, a 52 page manual is divided into 9 lessons. Superheterodyne receiver of standard AM and FM broadcast frequencies. Makes an excellent classroom project.
Photo courtesy Parts Express
Constructing your own FM/Ultrasonic/Infra Red Wireless Projects
RFID Application and Design
This project provides the basic of RFID and the application in the frequency range of 13.56MHz.
IR Remote Control Transmitter
This project is based on integrated circuit from Holtek Semiconductor HT6221/HT6222. These ICs are commonly used in television and VCR infra red remote controls, garage door controllers, car door controllers, security systems and other remote control applications.
Infrared Remote Control Decoding Project
This project based on Microchip 16C57 microcontroller decodes infrared remote control signals from television, VCR, air conditioner or other home appliances handset that uses NEC 6121 infrared format.
Infra Red Door Monitor
This door monitor project uses an infrared beam to monitor door & passageways or any other area. When the beam is broken a relay is tripped which can be used to sound a bell or alarm. Suitable for detecting customers entering a shop, cars coming up a driveway, etc.
9V FM Transmitters
Construct a FM transmitter in the range of 89MHz-109MHz. A simple LC tuned oscillator is used to generate the frequency needed in this educational project.
3V FM Transmitter
Schematic and the parts list needed to construct a 3V FM Transmitter.
FM Phone Transmitter
This device attaches in series to one of your phone lines. When there is a signal on the line (that is, when you pick up the handset) the circuit will transmit the conversation a short distance.
Ultrasonic Motion Detector
This device can be used to detect any moving object where it is installed. You can place it in the driveway, on the porch, garage, basement or any place where you need to be informed of any object that comes near the location.
Infrared Motion Detectors
This project is an excellent way for beginners of electronics and students to learn about the applications and concept of infrared devices.
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