Asked in ScienceEnvironmental IssuesPollutionLakes and Rivers
Lakes and Rivers
How many oscilations in 10 seconds from a source of frequency 1MHz?
Asked in Science, Electronics Engineering, Technology
What are the side bands in any of the modulation process?
If you have an RF (Radio Frequency) signal of 1MHz and you modulate it with a signal of 1kHz you end up with three frequencies 1MHz - 1kHz 1MHz 1MHz + 1kHz The carrier is 1MHz. The lower side band is 1MHz - 1kHz or 999kHz while the upper side band is 1MHz + 1kHz or 1.001MHz kHz is thousand cycles per second MHz is million cycles per second
Asked in Clocks and Watches
What is the timer count needed to create a time delay of 100 ms if the timer clock frequency is 1MHz?
Asked in Electronics Engineering, Radio
What is a super heterodyne receiver?
A superheterodyne receiver is a Radio Frequency receiver method that multiplies the received signal frequency with a local oscillator frequency to get frequencies that are the sum and difference of the 2 frequencies. For example, if the received signal is 5MHz and the local oscillator frequency is 4MHz, they are multiplied together. 1MHz and 9MHz frequencies would be gotten. Usually the 1MHz is the Intermediate Frequency (IF). It will be admitted (through a band pass filter) later passed through the required electronic circuits for proper processing. There is also the method of the Variable Tuned Filter.
What is the bandwidth and Q factor for a good tuned amplifier?
It depends on the signal you are trying to receive. For instance, the AM frequency band lies around 500KHz to 1700kHz. Lets say you have a tuned amplifier such that the resonant frequency was set roughly in the middle of that band at 1000kHz (1MHz). AM radio stations typically space out their broadcasts 9-10kHz. So if Q=f_resonant/f_bandwidth the Q of a tuned amplifier with a bandwidth of 10kHz (which would be decent, maybe a little spill over), would be: Q=1Mhz/10kHz Q=100 The higher the Q, the greater the selectivity. Too high be a bad thing too.
If something vibrates one million times per second it has a frequency of?
Asked in Computer Terminology
Which is bigger megahertz or gigahertz?
a more accurate query would be: Which is faster? quick answer: Gigahertz, meaning One Billion cycles per second. informative answer: hertz, (abbrevieated Hz) refers to a frequency, or rate of speed, of a recurring event. such as the rate at which a video screen flashes images, or the rate at which the special lights on emergency vehicles flash to activate automatic traffic signal 4-way stops. in technology, we use prefixes like mega- or giga- to describe specific amounts or frequencies of somethings, specifically capacity and cyclic frequency. your hard drive may have 100 gigabytes (capacity) of available space. you may have a 2 gigahertz (frequency) microprocessor. so using the International System of Units (look it up, I had to!) we find that mega- multiplies the singular by one million, and giga- multiplies by one billion. so a frequency of 1 GHz means 1 billion cycles per second, 1MHz means a million per second, and 1 Hz means only 1 cycle per second. this means 1GHz is a thousand times as frequent as 1MHz! -Very fast. :)
Asked in Physics, Chemistry, Elements and Compounds
What is the equation for wavelength?
Wavelength= the distance between successive identical parts of the wave(in meters) Ex. from crest to identical position in next crest. Wavelength is speed of transmission through the medium (usually speed of light) divided by frequency. For example, at the speed of light (3x108 meters per second), a 100MHz radio wave will have a wavelength of 3 meters, while a 1MHz radio wave will have a wavelength of 300 meters.
Asked in Physics
What are the kind of transmission is burst wave?
It is usually a set of sine waves of a specified frequency, for example 10, that start up and stop after the 10 are done. This is one burst, you can have repeating bursts. For example, bursts at a 10% duty cycle could be a burst of 20 cycles of 1MHz, which would take 20µs, then zero volts for 180µs, then another burst, etc. The rep rate of the bursts would be 5kHz in this example
Asked in Electronics Engineering
Why you need modulation?
for efficient radiation and reception the transmitting receiving antenna would have to have heights comparable to a quarter-wavelength of the frequency used .This is 75mtr for 1mhz but at 15khz it has increased to 5000mtr .A VERTICAL ANTENNA OF THIS SIZE is unthinkable Second all sound is concentrated within the range from20 Hz to20 kHz, so that all signals from the different sources would be hopelessly and inseparably mixed up .Therefore modulation be needed.
Asked in Computers
What is the clock speed measurement of a million cycles per second?
Asked in The Difference Between
What is the main difference between fdm and ofdm?
FDM and OFDM both have the same overlap!. In FDM the overlap is in the time domain. In OFDM the overlap is in the frequency domain. First (you may already know this) the relationship between the rectangular pulse and the sin(x)/x (sinc) function: A rectangular pulse in the time domain transforms to and from the sinc function in the frequency domain. A sinc function in the time domain transforms to and from a rectangular "brickwall" function in the frequency domain. In other words these two functions transform to each other by either FFT or IFFT. In both FDM and OFDM we are taking multiple carrier frequencies, modulating them, then combining them for transmission. For simplicity lets assume each carrier is on/off modulated. In idealized FDM, we modulate each carrier then send each though a brickwall filter before combining to the antenna. Say the carriers are separated by 500KHz, (say at 1GHz + 500KHz, 1GHz + 1MHz ...) Each carrier's 500KHz brickwall filter in the frequency domain cause a time domain spreading of its on/off pulses into time domain sinc function with zero crossings every 1us. Now, if we make the baud rate 1Mbps, each bit's ideal sampling point (center if eye) occurs at the zero crossing point of all of the potentially interfering sinc functions from previously received bits. In other words there is lots of ISI, but none at the critical moment when the bits are sampled. This is called "signalling at the Nyquist rate" and is related to but not the same as Nyquist sampling which you hear a lot about. (see en.wikipedia.org/wiki/Nyquist_ISI_criterion, apparently I am not allowed to include link because I am new to physicsforums). Of course brick wall filters are hard to make, so we use things like raised cosine filters that create the same beneficial sinc zero crossings. OFDM is analogous to FDM but with time and frequency domain reversed. We on/off modulate our carriers, but they are combined as unfiltered rectangular pulses and sent straight to the antenna (simplification of course). These time domain rectangular pulses become spread in the *frequency* domain as sinc functions. If we on/off modulate each carrier at 1Mbps (1us symbol time), and simultaneously maintain 1MHz carrier spacing ("orthogonal"), then the zero crossings of the sinc functions occur every 1MHz. Their positions are such that at each carrier frequency, all other carrier's smearing sinc functions have zero crossings. Thus each carrier frequency is free from interference. Again there is plenty of interference between these signals, but none at the critical frequencies where the carriers are located. Note the factor of 2 difference between the OFDM bandwidth and the FDM bandwith in my example. This is due to the convention of including negative frequency in the bandwidth in the OFDM case. Naturally, there is much more to it than this, but this is the basics. Hopefully you can figure out from this where the 50% comes from (look at the superimposed sinc functions).
Asked in Electronics Engineering
How envelope is eliminated and sine wave is produced in demodulation?
One way to demodulate an amplitude modulated signal from its carrier is to build a peak-follower. This could be a simple RC filter with a diode at the input. The voltage across the capacitor would charge to the peak value of the carrier (envelope), and then discharge through the resistor. The time constant would be selected so that the capacitor would have no "trouble" following the envelope. Since the typical ratio of signal to carrier frequency is quite high, i.e. 20kHz signal vs 1MHz carrier, the time constant can be quite short.
What is -3dbBpoint in the scope?
This is the freq at which the vertical amplifier is 70% of the low frequency response to a sinusoidal input. It's also called the roll off (or cut off) frequency. The vertical amplifier is what sits behind each of the channels on a scope, and allows you to "zoom in" on a signal in the vertical direction (amplitude). A 100MHz scope is capable of displaying a 100MHz sinusoidal waveform but just that it's going to show it at 70% of the amplitude that it displays at ,say, 1MHz. This assumes the input signal does not roll off in amplitude. The scope is able to display higher frequencies, it's just that it cannot react to higher and higher freq. The roll off is defined by a -6dB/octave "curve", which when plotted on a log freq scale is a negative slope above the cut off freq.
Why is there need for modulation?
Modulation is the process of varying a particular characteristic(amplitude,phase,frequency) of a high frequency carrier signal according to the message signal.The need of modulation is as follows:- 1.Reduces the height of antenna :-The minimum height of antenna required for transmission or reception of RF signals is one forth the wavelenth i.e lower the frequency,higher the wavelenght ,greater the length of the antenna .eg.for wave of 15Khz,antenna height is 5km,which is impractical but for 1Mhz wave,height is 75 m. 2.Increases the range of communication:-At low frequencies,radiation is poor and signal gets attenuated.Modulation effectively increases the frequency of the message signal and thus signal can be transmitted over longer distance without attenuation. 3.Avoids mixing of signals and allows multiplexing of signals:-When many signals are transmitted simultaneously,they may get mixed and it becomes difficult to separate them at the receiver end.This can be avoided by modulating different signals with different carriers i.e. each signal is allocated a separate bandwidth.At the receiver end,required signal can be intercepted by the tuning the receiver to desired frenquency bandwidth.This allows multiplexing(i.e. transmission of more than one signal simultaneously over the same channel.)eg.channels on television 4.Improves the quality of reception:-Modulation techniques like frequency modulation reduce the effect of noise and improve the quality of reception.
Asked in Microprocessors
What is the difference between Atmel microprocessor Atmega88-20pu vs Atmega88pv-10pu?
Asked in Computer Terminology, Microprocessors
CPU clock speed is measured in?
Asked in Bluetooth
Why piconet have limitation of only 8 devices?
i think because of the three bit (LT_ADDR), the logical transport address which is used by the master to identify the destination -the active slaves- and as u know 3 bit combination generates 8 codes. the second reason -not sure- because of the limitation of the physical channel (1MHz) which is time multiplexed in the piconet.
Asked in Science
Can humans hear all sounds?
You would think humans could hear all sounds but some can be below or above the frequancy of the humans ears:) +++ Very much so. For a healthy, fully function human ear, the lowest frequency is 2oHz, the maximum 20kHz, but age and long-term exposure to loud sounds will reduce the upper limit for an individual. Frequencies <20Hz are described as "infrasound"; made by some animals for communication. Frequencies >20kHz: ultrasound. Echo-locating bats call at around from 80kHz to above 100kHz when hunting (and some do so at very intensities, too, though at very low power as they are only little animals). Medical ultrasound frequencies exceed >1MHz.
Asked in Electrical Engineering
What is High frequency transformer?
High frequency power transformer as a product (ie goods) starting, that its design principles and requirements, and describes its design process. Keywords: High frequency power transformer; design principles; located Abstract: The high-frequency power transformer as a product (ie goods) starting, that its design principles and requirements, and describes its design process. Keywords: High frequency power transformer; design principles; design requirements; design process features a foreword power transformer is the power transfer, voltage transformation and isolation isolation, as a major soft magnetic components, power supply and power electronics technology been widely used. Transmission power according to the size, power transformers can be divided into several files: 10kVA or more for the power, 10kVA ~ 0.5kVA is in power, 0.5kVA ~ 25VA for the low-power, 25VA Following is a micro-power. Different transmission power, the power transformer design are not the same, should be self-evident. It was based on its primary function is the power transfer, the English name "Power Transformers" into "power transformer", in many documents and data are still in use. What is called "power transformer" or called "power transformer" is good? Science and technology terminology to be authority to select the decision. With an English name "Power Transformer", also translated as "power transformer." Power transformers used for power transmission and distribution system from the power transmission, voltage transformation and isolation insulating effect than the primary voltage is 6kV high-voltage, power minimum 5kVA, the largest over the million kVA. Power transformers and power transformers, although the working principle is based on the principle of electromagnetic induction, but both stressed the power transmission transformer big, but also stressed the high isolation voltage insulation, both in the **** coil, or the insulation structure design, with the power to send small , insulation and low voltage power transformer isolated significant differences, but can not be designed to optimize the design of power transformer condition mechanically applied to the power transformer to go. Power transformers and power transformer design method is not the same, it should be self-evident. High frequency power transformer is the operating frequency over frequency (10kHz) power transformers, high frequency switching power supply is mainly used for high frequency switching power transformers, but also for high-frequency and high frequency inverter power supply for high-frequency inverter welding machine inverter transformer. According to the level of the operating frequency can be divided into several grades: 10kHz ~ 50kHz, 50kHz ~ 100kHz, 100kHz ~ 500kHz, 500kHz ~ 1MHz, 1MHz or more. Larger transmission power, the operating frequency is relatively low; transmission power is relatively small, the operating frequency is relatively high. Thus, both the frequency difference, there are differences in transmission power, frequency of different grades of power transformer design is different, it should be self-evident. As noted above, of the high-frequency power transformer design principles, requirements and procedures are error concept, but in early July 2003, read "Application of Power" 2003 No. 6 specifically recommend two high-frequency magnetic components Design article, had doubts and felt some issues worthy of further discussion, it was to write this article. As the "power technology," Editorial put it: "concrete analysis of concrete situations," the purpose of writing is to try to detail and selection of the most difficult component of the magnetic high-frequency power transformer design to clarify . The place where it is wrong, please correct me by several authors and readers. 2 high-frequency power transformer high frequency power transformer design principles as a product of natural products with the properties, so high-frequency power transformer design principles and other commodities, is done under the specific conditions of use in the pursuit of specific performance of the functions price than the best. Emphasis on performance and efficiency may sometimes, sometimes emphasis on price and cost. Now, light, thin, short and small, to become the development direction of high frequency power supply is that of cost. Which became a major difficulty of the high-frequency power transformers, but more efforts in this regard. Therefore, high-frequency power transformer "design features" a text, talk about performance, not talk about the cost, can not be said to be a major shortcoming, if you will seriously consider the principle of high-frequency power transformer design, the pursuit of better performance and low cost to send less than 10VA the chip switching power supply high frequency transformers, should be designed lighter, thin, short, small programs. Cost aside, the market value of the law is merciless! Many properties of a good product, often because the price can not be accepted by the market who were left out and eliminated. Often the cost of a new product was finally rejected. Some "saving money is not festival" products why not open the market to promote worth pondering. Product cost, including not only material costs, production costs, including research and development costs, design costs. Therefore, in order to save time, based on past experience, high-frequency power transformer iron loss ratio of copper losses, leakage inductance and magnetizing inductance ratio, primary and secondary winding loss ratio, the current density to provide some reference data, the extent of the window fill winding wires and structure to some of the programs, what is wrong? Why must progressively projected back and forth and simulation, it is not the concept of error? Of 80 years in the 20th century to develop high-frequency magnetic amplifier switching power supply to the lowest temperature conditions, optimized high-frequency power transformer design. Difficult to determine the thermal resistance, a far cry from the sample results and trial had again amended. Now some of the company's **** product specifications in order to reduce the user time high-frequency power transformer, and some simplified design formulas are listed, some with the table lists the **** operating frequency in a certain transmission power. This not only for the sake of users, but also to promote the company's products win-win behavior is entirely consistent with the behavior of market rules, not what is needed misconceptions Analysis. The problem is to provide reference data, the recommended solution is a summary of experience? There is no universal? Including the "Analysis" article to some of the claims, we need proven to hold water. In short, do keep in mind: high-frequency power transformer is a product (ie, commodities), the design principle is to be completed under the specific conditions of use of specific functions in the pursuit of best price performance. The sole criterion for testing the design is to design products that can withstand the test of the market. 3 high-frequency power transformer design requirements to design principles as a starting point, you can make four high-frequency power transformer design requirements: Conditions, completion, improve efficiency and reduce costs. 3.1 Conditions of Use Conditions of Use, including two aspects: reliability and electromagnetic compatibility. Previously only pay attention to reliability, since the increased awareness of environmental protection, must pay attention to electromagnetic compatibility. Reliability refers to the specific conditions of use, high-frequency power transformer can work to life so far. General Conditions of Use of High Frequency Power Transformer is the biggest environmental temperature. Some soft magnetic materials, relatively low Curie point, temperature sensitive. For example: Mn-Zn ferrite, the Curie point only 215 ? the magnetic flux density, permeability and loss changes with the temperature, so the addition to the normal temperature of 25 ? but also gives the 60 ? 80 ? 100 ? a variety of reference data. Therefore, Mn-Zn ferrite **** of the operating temperature limits below 100 ? which is the ambient temperature is 40 ? the temperature rise of only less than 60 ? the equivalent of A-temperature insulating materials. Mn-Zn ferrite cores with the matching pieces of magnet wire and insulation, are generally used E-class and B class insulation material, the use of triple H class insulation magnet wire and polyamide insulating film, is not overkill? Costs how much? H class insulation is not because of the high-frequency power transformer design optimization can make the volume reduced by 1 / 2 to 1 / 3 the reason? If yes, please give specific examples of data. Development of the H class insulation has frequency 50Hz, 10kVA dry-type transformers, and insulation class B frequency 50Hz, 10kVA dry-type transformers compared to volume decreased 15% to 20%, is already quite substantial. Have been relatively small volume of high-frequency 100kHz10VA high frequency power transformers, such as the secondary windings are triple insulated wire, can reduce the size of 1 / 2 to 1 / 3, it must be a very valuable experience. Detailed information about optimal design of programs for readers to learn.
What are the limitation of crystal oscillators and why?
about 100mhz upper limit this is a mechanical vibration in a piece of quartz sound travels about 1000ft a second 1 ft crystal is 1000 hz 1/8 inch 1Mhz 0.0002 in = 1Ghz crystals in about 30Mhz are generally 3rd harmonic so perhaps .040 " is a practical limit ... experimenters have made them thinner but its usually a thin flat spot in the middle of a thicker piece the crystal in your watch is of tuning fork variety held at the edge swings side to side so it doesnt need to be 3" thick they settled on about 1/4" long and divide by 32768 in a ripple counter so you can see seconds a meter long or so on the tuning fork crystal ought to give seconds directly would be fine for a wall clock maybe there is also a power limitation quartz breaks if bent beyond its elastic limit has nice stability till then
Asked in Mobile Phones, India, Wireless Communication
Can someone give the list of license free frequency band in India?
Yes! ---------------------------------------------------------------------------------------------------------- Use : Low power RFID equipments or any other low power wireless devices or equipments Frequency Band: 865-867 MHz Power: Maximum transmitter output power of 1 Watt ( 4 Watts Effective Radiated Power) Carrier Bandwidth: 200 KHz Reference: GSR 564 ( E) dated 30 July 2008 ---------------------------------------------------------------------------------------------------------- Use : Low power equipments Frequency Band: 2.4-2.4835 GHz Power: Maximum transmitter output power of 1 Watt ( 4 Watts Effective Radiated Power) Carrier Bandwidth: spectrum spread of 10 MHz or higher Reference: GSR 45E dated 28.1.2005 ---------------------------------------------------------------------------------------------------------- Use : Low power equipments for Cellular telecom systems including Radio Local Area Networks, Indoor applications Frequency Band: 5.150-5.350 GHz, 5.725 - 5875 Power: maximum mean Effective Isotropic Radiated Power of 200mW, maximum mean Effective Isotropic Radiated Power density of 10mW/MHz in any 1 MHz bandwidth, Carrier Bandwidth: 1MHz Reference: GSR No 46E dated 28.1.2005 ---------------------------------------------------------------------------------------------------------- Use : Low power equipments Frequency Band: 5.825 to 5.875 GHz Power: maximum transmitter output power of 1 Watt ( 4 Watts Effective Radiated Power) Carrier Bandwidth: spectrum spread of 10 MHz or higher Reference: GSR no 38E dated 19.1.2007 ---------------------------------------------------------------------------------------------------------- Use : Wireless equipments intended to be used while in motion or during halts Frequency Band: 26.957-27.283 MHz Power: maximum Effective Radiated Power ( ERP) of 5 Watts Reference: GSR no 35 E dated 10.01.2007 ---------------------------------------------------------------------------------------------------------- Use : Low power equipments for the remote control of cranes Frequency Band: 335.7125, 335.7375, 335.7625, 335.7875, 335.8125 and 335.8375 MHz Power: maximum transmit power of 1mW Carrier Bandwidth: 10 KHz Reference: GSR 34( E) dated 10.1.2007 and GSR 532 ( E) dated 12.8.2005 ----------------------------------------------------------------------------------------------------------