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Topic: Frequency spectrum

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In the News (Sun 16 Jun 19)

  Howstuffworks "How the Radio Spectrum Works"
In the same way, AM radio is confined to a band from 535 kilohertz to 1,700 kilohertz (kilo meaning "thousands," so 535,000 to 1,700,000 cycles per second).
The first radio broadcasts occurred in 1906 or so, and frequency allocation for AM radio occurred during the 1920s (The predecessor to the FCC was established by Congress in 1927.).
Television stations were pretty much non-existent until 1946 or so, which is when the FCC allocated commercial broadcast bands for TV.
electronics.howstuffworks.com /radio-spectrum.htm   (680 words)

 [No title]
Further, the quasi half-period of the components of the oscillatory portion was found to obey a relation different from the /`slow tail/'.During the past few years we have supplemented the waveform observations by simultaneously recording the different frequency components in the spectrum of atmospherics from the response of a number of narrow-band tuned receivers3.
The amplitude frequency spectrum is presented directly on the screen of a cathode-ray tube and photographed with the corresponding waveform in order that there should be no doubt as to the type of atmospheric to which the spectrum relates.
Frequency of maximum components in the oscillatory portion of atmospherics compared with results deduced from waveform observations by Watson-Watt (indicated as W.-W.) at various distances from the source.
www.nature.com /nature/journal/v172/n4376/ris/172495a0refs.ris   (852 words)

  Shirky: The Possibility of Spectrum As A Public Good
Spectrum, in the aggregate, is just a collection of waves, and a wave is defined by its characteristic frequency, measured by counting the number of waves that pass a given point in a second -- the more waves, the higher the frequency.
Treating frequency as a wire also sets limits on the amount of data that can be transmitted, since the data is encoded as minor changes to the waves themselves In the frequency-as-wire model, the higher the frequency of waves, the higher the data rate, and the lower, the lower.
Spectrum is purely descriptive -- a frequency is just a particular number of waves a second -- so no one can own a particular frequency of spectrum in the same way no one can own a particular color of light.
shirky.com /writings/spectrum_public_good.html   (2836 words)

 Science Fair Projects - Frequency spectrum
In mathematics, physics and signal processing, the frequency spectrum shows the decomposition of a function, or wave, or signal, into its frequency components (the sinusoidal basis functions of the Fourier series).
Ideally, one would use the full Fourier transform to compute the frequency spectrum, but often only a finite set of discrete samples is available, in which case one generally applies spectral estimation techniques to some form of discrete Fourier transform.
Besides being important in mathematics and physics, the spectrum amplitude versus frequency is very important for digital signal processing and for audio processing software that needs to recognize the frequency of the signal before processing it.
www.all-science-fair-projects.com /science_fair_projects_encyclopedia/Frequency_spectrum   (686 words)

 Physikalisch-Technische Bundesanstalt (PTB)
Optical frequency measurement and the related developement of atomic clocks and optical frequency standards is an important and rapidly evolving area of research.
Both the relation of the microwave and the optical region and the operation of an optical frequency standard as a clock requires a sort of a "clockwork" for a coherent, noise-free link of large frequency ratios.
1, the special feature of the laser is the frequency spectrum consisting of a large number of exactly equidistant modes, which, pictorially spoken, correspond to the mm markers on a ruler.
www.ptb.de /en/org/4/44/444/feseka_e.htm   (440 words)

 PC-Based Spectrum Analyser   (Site not responding. Last check: )
The spectrum analyser is inbuilt with a swept oscillator or a Tracking generaro which is a signal source, has an output whose frequency same as the swept frequency of the Analyser.
For frequencies more than 100KHz the output of the DAC is fed into an external sweep oscillator and the output frequency of the external sweep oscillator is fed to the device under test.
A cursor is given to scroll througout the frequency spectrum and to view the corresponding frequency and gain in the particular point.
www.angelfire.com /in/dgraj/spectrum.html   (825 words)

 frequency spectrum- Developer Zone - National Instruments
The frequency spectrum is useful for identifying repeating signals, of which a sine wave is the simplest.
The spectrum consists of a number of periodic components (one vector per frequency), which are most often displayed as magnitude and phase information.
Frequency response refers to the transfer characteristic of a system, that is, the input/output relationship.
zone.ni.com /devzone/cda/tut/p/id/885   (1237 words)

 Kids.Net.Au - Encyclopedia > Frequency spectrum
The frequency spectrum is the result of a frequency transform of a function.
As opposed to the power spectrum, the frequency spectrum should not only include the energy distribution among the frequency domain but also spatial or phase angle information.
Most commonly, the Fourier transform is used as frequency transform.
www.kids.net.au /encyclopedia-wiki/fr/Frequency_spectrum   (87 words)

 Electric arc and radio frequency spectrum detection - Patent 5373241
The mixer 37 may be fed from a radio frequency signal unbalanced to balanced converter (32) having an input (25) coupled to a source of the signal having the spectrum and having balanced outputs connected to the mixer inputs (35, 36).
Similarly, the components 32, 33 and 34 constitute a radio frequency signal duplicator having an input coupled to a source of the spectrum to be detected, a first output at 33 for one spectrum as duplicated by that duplicator, and a second output at 34 for the other spectrum as duplicated by that duplicator.
The frequency combination detector may include first means 42 for generating a first signal proportional to a signal level at the mixer output 38, and second means 142 for generating a second signal in response to frequency or phase offsets in the radio frequency mixer 37.
www.freepatentsonline.com /5373241.html   (4409 words)

 Frequency spectrum - Definition, explanation
In mathematics, physics and signal processing, the frequency spectrum is a representation of a signal or other function in terms of frequency (in the "frequency domain").
The "spectrum" of a sample of electromagnetic radiation (light), intuitively considered to be its decomposition into colors, can be interpreted more rigorously as the frequency spectrum of the oscillation of the electromagnetic field.
Thus, a frequency spectrum of a beam of light can also be interpreted as the energy spectrum of a beam of photons.
www.calsky.com /lexikon/en/txt/f/fr/frequency_spectrum.php   (620 words)

 Telkom SA Limited   (Site not responding. Last check: )
On February 21, 1997, we were deemed to be the holder of a radio frequency spectrum license to provide telecommunication services and facilities, and on May 7, 1997, we were issued a written license by the Minister for Posts, Telecommunications and Broadcasting to use the relevant bands of radio frequency spectrum.
Our use of the radio frequency spectrum is subject to our compliance with the relevant provisions of international telecommunications conventions, the radio regulations and the International Telecommunications Union radio regulations agreed to or adopted by the Republic of South Africa.
Our radio frequency spectrum license may be revoked by ICASA if we repeatedly fail to comply with an order made by it and fail to correct the non-compliance within 90 days of being requested to comply, or if we are placed in final liquidation or under a provisional or final judicial management order.
www.telkom.co.za /minisites/ir/markcontex/reg_othlicenc.html   (488 words)

 Physics Today March 2004- Acoustics Experiment Shows Why It's So Hard to Make Out the Heroine's Words at the Opera
Adjacent to a microphone touching the subject singer's lower lip is an acoustical current source--the output horn of an electronic sound synthesizer that is calibrated to present the microphone with a flat broadband frequency spectrum when the singer is silent with her mouth closed.
Thus the frequency spectrum recorded by the microphone (see figure 1) combined the narrow spikes of the singer's fundamental pitch frequency and its overtones with the much broader, but still well-defined, peaks that exhibit the modification of the synthesizer output by the resonances in that particular vocal-tract configuration.
The first resonance of an unflared cylinder is at the frequency for which the cylinder's length is 1/4 of the wavelength of a standing acoustic wave.
www.physicstoday.org /vol-57/iss-3/p23.html   (1461 words)

 Radio Frequency Allocations for Meteorological Operations and Research (Adopted by AMS Council 10 January 1999
The scientific uses of the radio frequency spectrum are expanding as the weather community increasingly moves toward remote sensing for routine weather measurement and prediction.
Current and planned uses of the radio frequency spectrum for passive, radiometric meteorological measurements are illustrated in Table 1, which includes a majority of the passive uses of the radio frequency spectrum for current or planned satellites that provide measurements for meteorological and earth system science studies.
The uses of the radio frequency spectrum for passive measurement are changing as new techniques are developed, and in some cases these passive uses of the radio spectrum extend outside formally allocated bands.
www.ametsoc.org /policy/radiofrequencyallocations.html   (1081 words)

 FCW.com - Defense rethinks its wireless needs
As it updates its spectrum policies, DOD is seeking more industry partnerships to achieve its goal of balancing military and commercial interests, he said.
Flexibility in spectrum use is a win-win situation for government and industry, said Peter Pitsch, director of communications policy at Intel.
If spectrum regulations are relaxed, Pitsch said, industry will have an incentive to create more spectrum-efficient technologies, thereby reducing pressure on the government to share spectrum.
www.fcw.com /article96687-11-06-06-Print&printLayout   (794 words)

 ABCs of Spread Spectrum - A Technology Introduction and Tutorial
The result of modulating an RF carrier with such a code sequence is to produce a signal centered at the carrier frequency, direct sequence modulated spread spectrum with a (sin x/x)2 frequency spectrum.
Frequency hopping systems -- The wideband frequency spectrum desired is generated in a different manner in a frequency hopping system.
The specific order in which frequencies are occupied is a function of a code sequence, and the rate of hopping from one frequency to another is a function of the information rate.
www.sss-mag.com /ss.html   (2761 words)

 FFT Properties
It is a frequency spectrum of the signal with frequency of 1Hz and amplitude of 1V.
The whole spectrum is polluted by a full bandwidth of frequencies that are not present in the original signal at all.
If the frequency of the signal falls between two lines, and we do not apply zero padding (spectrum oversampling) it is almost impossible to say what is the actual frequency of that signal or the actual amplitude.
www.teemach.com /FFTProp/FFTProperties/FFTProperties.htm   (3940 words)

 Frequency Modulation
Changing the spectrum analyzer setting from one mode to another is accomplished by varying the scan time and the bandwidth of the spectrum analyzer or a combination of the two.
Most real-time spectrum analyzers, however, are preceded by mechanical filters, which limit the input bandwidth of the spectrum analyzer to the desired spectra to be analyzed.
Scan time of the spectrum analyzer must be long enough, with respect to the amplitude of the signal to be measured, to allow the IF circuitry of the spectrum analyzer to charge and recover.
www.tpub.com /neets/book21/90d.htm   (1152 words)

 CHIPS - The Department of the Navy Information Technology Magazine
As a device is developed, the spectrum community is able to provide the guidance necessary to successfully operate the system in the congested, highly regulated radio frequency spectrum environment.
Frequency assignment is the licensing of an individual radio frequency in a particular geographic area.
Years ago, radio frequency spectrum management was done with mechanical slide rules, formulas, best guesses, rules of thumb and hours or sometimes days of labor to predict characteristics of the electromagnetic environment.
www.chips.navy.mil /archives/05_Oct_Dec/web_pages/spectrum.htm   (1535 words)

 OET -- FCC Radio Spectrum Home Page
The radio spectrum is the radio frequency (RF) portion of the electromagnetic spectrum.
In the United States, regulatory responsibility for the radio spectrum is divided between the Federal Communications Commission (FCC) and the National Telecommunications and Information Administration (NTIA).
OET maintains the FCC's Table of Frequency Allocations, which is a compilation of allocations.
www.fcc.gov /oet/spectrum   (544 words)

 Spartanburg SC | GoUpstate.com | Spartanburg Herald-Journal   (Site not responding. Last check: )
Radio frequency, or RF, refers to that portion of the electromagnetic spectrum in which electromagnetic waves can be generated by alternating current which is fed to an antenna.
Such frequencies and the belonging wavelength account for the following parts of the frequency spectrum shown in the table below.
The SHF and EHF bands are often considered to be not part of the radio spectrum and form their own microwave spectrum.
www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=radio_frequency   (359 words)

 Radio frequency spectrum
Above 300 GHz, the absorption of electromagnetic radiation by Earth's atmosphere is so great that the atmosphere is effectively opaque to higher frequencies of electromagnetic radiation, until the atmosphere becomes transparent again in the so-called infrared and optical window frequency ranges.
The SHF and EHF bands are often considered to be not part of the radio spectrum and form their own microwave spectrum.
Frequencies from 216 to 450 MHz were sometimes called P-band: Previous, since early British Radar used this band but later switched to higher frequencies.
faculty.cs.tamu.edu /lively/GE_rf/radio_frequency_spectrum.htm   (390 words)

 Electric arc and radio frequency spectrum detection - Patent 5477150
A principal object of the invention is to detect sparks or arcs (12) in electric circuits (13) or otherwise to detect a spectrum of a broad band of distinct instaneous radio frequencies in radio frequency noise.
a frequency combination detector having an input coupled to said radio frequency mixer output, and having an output for a signal indicative of a detected combination of said distinct instantaneous radio frequencies in contradistinction to said extraneous narrow-band signals.
In the illustrated embodiment, the output of the frequency ccnverter or mixer 37 is the result of an instantaneous difference frequency between any two or more of the nearly continuous noise pulses which make up the wide band RF signature of the arc being detected.
www.freepatentsonline.com /5477150.html   (4983 words)

 Understand Bio-Frequency Spectrum   (Site not responding. Last check: )
Bio-Frequency Spectrum (BFS) is a nomenclature for both the frequency and spectrum of physical information emanating from living body itself.
Emission spectrum of human body was measured of human body as a Whole using infrared wave spectrum meter and millimeter wave meter.
Spectrum responses in the tissue pieces of liver, muscular tissue skin and blood samples obtained from surgical operation were assayed.
www.ib3health.com /products/TDP/TDP_BioSpectrum.shtml   (2504 words)

 Spectrum Analyzers - Nicom LLC
With the 8553B plug in, the frequency range of the analyzer is from 1KHz to 110MHz with 18 calibrated scan widths from 20Hz/div to 10MHz/div.
Frequency span division range is 10KHz to 500MHz/div in a 1 - 2 - 5 sequence in the ranges of 500Hz, 1KHz, 2KHz, and 5KHz divisions.
The 7L13 spectrum analyzer plug-in performs basically the same functions as the 7L12 including a digital center frequency readout and a light that indicates when the unit is not working in calibrate mode.
www.nicomusa.com /surplus/analyzer02.htm   (2434 words)

 Radio Spectrum Wars   (Site not responding. Last check: )
The average citizen is familiar with the radio spectrum through enjoyment of AM and FM radio, television, short wave radio, amateur radio, and the use of ancillary items, such as garage door openers, cordless phones, microwave ovens, and wireless computer networks.
The frequency range between 1.42 and 1.64 GHz is sometimes called the “water hole,” and it is a critical band for research and for the Search for Extraterrestrial Intelligence (SETI).
The frequencies previously allocated to satellite downlinks in the 71-275 GHz range were reset at frequencies not presently being used for scientific purposes.
www.3towers.com /RadioSpectrumWars.htm   (1669 words)

The result is a data signal that has been spread across a wider frequency spectrum, so to an unintended receiver, it appears as low-power wideband noise and is ignored.
FHSS is a transmission technology that uses a narrowband carrier signal that changes frequency (hops) in a random but predictable pattern as a function of time over a band of frequencies that is known by both the transmitter and receiver.
Portion of the radio-frequency spectrum allocated by regulatory agencies (e.g., the FCC in the United States) and international agreements to local use for industrial, scientific, medical, domestic and other similar applications, excluding telecommunications.
www.pnl.gov /wireless-buildings/glossary.htm   (459 words)

 On-Line Glossary of Solar-Terrestrial Terms
A portion of the electromagnetic spectrum from approximately 100 to 1000 angstroms.
Of the white-light CORONA (that is, the corona seen by the eye at a total solar (ECLIPSE), that portion which is caused by sunlight scattered or reflected by solid particles (dust) in inter- planetary space.
The maximum ORDINARY MODE radiowave frequency capable of reflec- tion from the SPORADIC E REGION of the IONOSPHERE.
www.sec.noaa.gov /info/glossary.html   (3279 words)

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