
	Where results make sense

Topic: Frequency accuracy

	Time and Frequency
		Frequency standards, particularly optical frequency standards, based on stored ions have the potential for higher accuracy than the best current standards, which are based on the neutral cesium atom with a transition in the microwave region, since observation times are much longer and fractional linewidths are much smaller.
		The first atomic frequency standard, based on ammonia, was built in 1950 at NIST in Washington, D.C. Since then, we have constructed a series of seven standards based on cesium beams with performances improving at a rate of better than an order of magnitude every 10 years.
		The accuracy of measurement is typically one decibel or better depending on the frequency range.
	www.nist.gov /public_affairs/guide/time_frequency.htm (762 words)

	Time and Frequency from A to Z
		Accuracy is the degree of conformity of a measured or calculated value to its definition.
		In the world of time and frequency, accuracy is used to refer to the time offset or frequency offset of a device.
		Frequency offset is the difference between a measured frequency and an ideal frequency with zero uncertainty.
	tf.nist.gov /timefreq/general/glossary.htm (838 words)

	Introduction to Quartz Frequency Standards - Accuracy, Stability, and Precision (Site not responding. Last check: 2007-10-25)
		These include aging, noise, and frequency changes with temperature, acceleration, ionizing radiation, power supply voltage, etc. The terms accuracy, stability, and precision are often used in describing an oscillator's quality with respect to its instabilities.
		Accuracy is the extent to which a given measurement, or the average of a set of measurements for one sample, agrees with the definition of the quantity being measured.
		A primary standard operates at a frequency calculable in terms of the SI definition of the second: "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium atom 133" [15].
	www.ieee-uffc.org /freqcontrol/quartz/vig/vigaccur.htm (345 words)

	Center for Computational Biology
		For the forward filter, each frequency component of the cross-correlation is normalized by the power of the stimulus at the corresponding frequency, whereas for the reverse filter, this normalization is done using the power of the spike trains.
		We were thus unable to assess either the frequency sensitivity range of the cells or the possibility of any nonlinearities in their responsiveness to combinations of several different stimulus frequency components.
		The frequency tuning of a neuron, as measured by its encoding accuracy; depends on the reliability (measured by the variance around a mean value) with which its spikes phase lock to each of the individual frequency components of the dynamic stimulus.
	cns.montana.edu /research/pub/infotheodynenc96 (15792 words)

	Radio-Electronics.Com :: Frequency Counter Accuracy and Resolution
		Frequency counters are widely used for the measurement of frequency of radio frequency, RF, signals, or for that matter the frequency of any repetitive electronic signal.
		The accuracy of a frequency counter is a little more difficult to determine as it is a function of a number of factors.
		The errors introduced on the frequency counter reading may result from the basic frequency accuracy of the timebase, the ageing rate, temperature variation and the variation with line voltage.
	www.radio-electronics.com /info/t_and_m/frequency_counter/counter_accuracy.php (881 words)

	Time and Frequency from A to Z
		Since accuracy is related to the offset from an ideal value, frequency accuracy is usually stated in terms of the frequency offset.
		Frequency drift may be in either direction (higher or lower frequency) and is not necessarily linear.
		Frequency mixers are commonly employed in frequency measurement systems (as shown in the graphic below), to convert a high frequency to a low frequency, and to obtain more measurement resolution.
	tf.nist.gov /general/enc-f.htm (985 words)

	Making RF Power and Frequency Measurements with Spectrum and Signal Analyzers - Tutorial - Developer Zone - National ...
		The accuracy of frequency measurements at most points in the display is limited by the accuracy of the analog ramp signal.
		The accuracy of frequency measurement is uniform across a given frequency span, therefore no particular optimization such as placing the signal of interest in the middle of the span to improve accuracy is required.
		Accuracy across the frequency span is solely dependant on the timebase accuracy and the measurement algorithm, thus better frequency accuracy and repeatability are much easier to obtain.
	zone.ni.com /devzone/conceptd.nsf/webmain/F09665F0A4E6C35E86256D2F00760038?opendocument&node=dz00000_us (2844 words)

	NIST Time and Frequency Div. - 2002: Strategic Focus 1
		The strategy of the Time and Frequency Division is to advance measurement science and to provide time and frequency standards and measurement services to commerce and industry.
		The accuracy of the NIST time scale is derived from the current primary frequency standard, NIST-F1, a cesium-fountain standard with a relative frequency uncertainty of 1 fHz/Hz.
		Since the accuracy of frequency standards has improved by more than an order-of-magnitude every decade since 1950, and practical applications have historically always followed these advances, an aggressive program of research and development in this area is easily justifiable.
	physics.nist.gov /TechAct/Div847/div847.html (1216 words)

	Introduction to Quartz Frequency Standards - Oscillator Comparison and Selection
		Accuracy versus cost would be a similar relationship, ranging from about $1 for a simple XO to about $40,000 for a cesium standard (1991 prices).
		n atomic frequency standards, the output signal frequency is determined by the energy difference between two atomic states, rather than by some property of a bulk material (as it is in quartz oscillators).
		It consists of a rubidium frequency standard, a low-power and high-stability crystal oscillator, and control circuitry that adjusts the crystal oscillator's frequency to that of the rubidium standard.
	www.ieee-uffc.org /freqcontrol/quartz/vig/vigcomp.htm (792 words)

	Frequency Standards - An Introduction
		Frequency Accuracy: This is the degree of conformity to a specified value of a frequency.
		The oscillator phase noise is a significant parameter, since it used to modulate the signal frequencies and ultimately affect the purity of the transmitted/received signal.
		Stability: Oscillators frequency stability is defined as the measure of the degree to which an oscillator maintains the same value of frequency over a given time.
	www.tutorialsweb.com /rf-measurements/frequency-standards/frequency-standards-index.htm (779 words)

	AA6E Station Log: Orion Frequency Calibration (Site not responding. Last check: 2007-10-25)
		The Ten-Tec Orion Transceiver is specified for frequency accuracy of + or - 3 ppm over the temperature range 0 - 50 C. That amounts to +/- 30 Hz at 10 MHz, or nearly +/- 90 Hz in the 10 meter band.
		The most likely case where good accuracy can help in the HF bands is when we operate in roundtable mode on SSB.
		If we don't have good accuracy, and if we don't all tune up carefully on one station, we may have to use the RIT every time a different person is speaking.
	blog.aa6e.net /2005/08/orion-frequency-calibration.html (1043 words)

	IEEE P1159
		The accuracy of an indicated or recorded value is expressed as the percentage of the error of the indicated value to the true actual value.
		Frequency deviations can affect the performance of electronic timers, where a timing interval is determined by detecting the zero-crossings of the ac supply voltage.
		The objective of the frequency measurement test protocol is to determine the ability of a test instrument to properly report the frequency of a standard input signal.
	grouper.ieee.org /groups/1159/1/IE1159_1.html (3893 words)

	5071A - Primary Frequency Standard (Site not responding. Last check: 2007-10-25)
		The 5071 offers exceptional frequency stability which is a key specification that directly affects a laboratory's ability to deliver timekeeping and calibration services to its clients.
		Stable frequency generation and frequency flexibility are required to transmit and receive signals properly between ground terminals and communication satellites.
		Timing accuracy for the GPS system is based, in large part, on the accuracy and stability of a number of 5071A primary frequency standards.
	www.symmttm.com /pr_lp/5071A (371 words)

	Fractional-N synthesis improves reference-frequency implementations - 6/13/2002 - EDN (Site not responding. Last check: 2007-10-25)
		For low-power radio applications, a frequency error of ±5 ppm allows the bandwidth of the channel-select filter to be narrow enough to achieve good receiver sensitivity and sufficient rejection of the busy adjacent channels in the ISM bands.
		The accuracy of direct-digital-frequency compensation is limited by how closely the crystal follows the estimated temperature-characteristic curve, the accuracy of the ADC and DAC, and the predictability of the capacitance of the varactor diode.
		The accuracy of indirect-digital-frequency compensation is limited by how closely the crystal follows the estimated temperature-characteristic curve and the accuracy of the temperature sensor.
	www.edn.com /article/CA220399.html (2687 words)

	R&D at the Telecommunications Laboratory (Site not responding. Last check: 2007-10-25)
		The High-Accuracy Carrier Frequency Level Test Set type ET-100 is rendered by its wide frequency band (0.2...1620 kHz) and its high frequency accuracy and 4kHz locked system suitable for execution of setting up, operating and maintenance measurements of 300 channel FDM systems.
		The frequency adjusted on the main tuner can be modified within a +4 kHz range by means of fine turner f2, with correct sign, according to the straight or reverse allocation of the channel to be measured.
		Adjustment and indication of the frequency is brought about in a manner similar to that of employed for the level oscillator.
	tel.ttt.bme.hu /Num3/et100.html (972 words)

	Accuracy of frequency domain analysis scenarios for the determination of complex dielectric permittivity
		Frequency domain analysis of time domain reflectometry waveforms has been shown to be useful for more accurate water content determination, water content determination in saline soils, and determination of such difficult to measure soil properties as specific surface area and soil solution conductivity.
		Earlier frequency domain analysis approaches to determine frequency-dependent dielectric properties of soils have used a variety of methods.
		However, frequency domain analysis of ethanol measurements showed that results were susceptible to model errors caused by nonideal probe behavior.
	www.agu.org /pubs/crossref/2004/2002WR001601.shtml (516 words)

	Frequency accuracy
		The frequency of a quartz crystal oscillator does vary with temperature, but not nearly so much as a tuning fork.
		There are things that a designer can do to stabilize the frequency, such as include compensating elements (usually capacitors) that have opposite temperature characteristics from the quartz crystal, and so cancel out most of the frequency variations.
		Some years ago I tried to get our local phone company to commit to what the accuracy of that A-440 was, but they could give me no assurances that any particular accuracy would be maintained.
	www.ptg.org /pipermail/pianotech/1999-June/048374.html (338 words)

	Frequency Calibration (Site not responding. Last check: 2007-10-25)
		The Austin EMC frequency standard is a battery backed-up, disciplined quartz oscillator that is phase locked to the Raymondville, Texas slave station of the South Central U.S. Loran-C navigation chain.
		Fractional frequency offset uses the HP5345 to measure the time difference accumulated between two phase locked Frequency Synthesizers set to 100 Mhz.
		When both frequencies are equal the time difference will be a constant 10 Nanoseconds which can be measured with a resolution of 2.02 picoseconds in 100 seconds.
	www.austinemc.com /fcal.htm (296 words)

	ARRL FMT - Observations, techniques and comments
		Knowing the RF frequency of the locally-generated signal, the audio frequency of that signal as produced by the receiver and the precise audio frequency of the W1AW signal allows the one remaining unknown to be easily calculated: The RF frequency of the W1AW signal.
		Because this is an indirect system of frequency measurement and because it is based on relative measurements, the frequency accuracy of the receiver itself is unimportant: The onus is on accuracy of the locally-generated signal.
		As a reminder, note that the audio frequency shown on the spectral display is not exactly that of the audio frequency: The displayed frequency was referenced to the locally-generated carrier and the actual RF carrier frequency was thus determined.
	www.ka7oei.com /fmt.html (2952 words)

	ARRLWeb: Accuracy in Frequency Measuring Tests!?
		For weeks before the recent Frequency Measuring Tests I had brayed to my friends on the air about how I would make a concerted effort to place high on the FMT results list.
		It was disturbing to discover that receiver dial backlash and frequency drifting were a real problem at those last hours, when attempting to tune and maintain zero phase difference, so I haywired a multiturn vernier capacitor across the receiver p.t.o.
		Actually, the frequency seldom drifts more than a few cycles during the entire transmission period, so any significant differences will be noted only when precision measuring equipment is in use.
	www.arrl.org /w1aw/fmt/fmt-accuracy.html (696 words)

	MAX2392 Meets TD-SCDMA UE Phase Noise Requirements - Maxim/Dallas
		The frequency stability is the difference of the modulated carrier frequency between the RF transmission from the UE and the RF transmission from the BS.
		The UE frequency stability, observed over a period of one timeslot, shall be within ±0.1 ppm compared to signals received from the BS.
		When UE base band estimates the received signal's carrier frequency, this average frequency error will be equal to the estimated frequency error, and the transmitting path LO will result in additional frequency error, the total frequency error is then the sum of Rx and Tx average frequency error.
	www.maxim-ic.com /appnotes.cfm?an_pk=3036 (990 words)

	60 Hz AC Mains Frequency Accuracy Measurement (Site not responding. Last check: 2007-10-25)
		The integrated frequency, or time-keeping aspect of frequency, is also quite accurate.
		It is not that difficult to devise a circuit that marks zero-crossings of the 60 Hz AC waveform.
		The columns are instantaneous frequency, instantaneous phase change, net phase gain/loss since power-up, mains hour, minute, second, and UTC hour, minute, second.
	www.leapsecond.com /pages/mains (376 words)

	Frequency-Response Method for Rotorcraft System Identification: (Site not responding. Last check: 2007-10-25)
		The frequency sweeps are used for model identification with CIFER, while the 3211 and doublet data are reserved for verification.
		The natural frequency of the lead-lag response corresponds to the peak in the response at 15.5 rad/sec displayed in Fig.
		In the higher frequency range of 9-30 rad/sec, the hybrid model matches the roll frequency-response data very well (especially compared to the 6-DOF model as shown in the figure) indicating that the simple rotor modeling for the high-frequency response is adequate.
	caffeine.arc.nasa.gov /cifer/journal/ahsj.html (7076 words)

	Brooks Shera's GPS-controlled Frequency Standard
		The goal was to produce an inexpensive, but highly accurate, frequency standard by synchronizing a local crystal (or Rb) oscillator to the GPS atomic clocks.
		Below is a picture of the controller together with a GPS antenna and, in the background, a 20 year old HP frequency standard that is locked to the GPS atomic clocks by the controller.
		The residual 1 ns jitter produces the spurious short-term frequency corrections of a few parts in 10 to the 11 that are evident in the expanded plot.
	www.rt66.com /~shera/index_fs.htm (1778 words)

	Crystals
		In either case becasue of stray capactance either the frequency will be off some or there will be a variable capacitor to adjust the frequency.
		A low cost unit oscillator may have a frequency variation of a few Hz when measured using a 1 second integration time counter whereas a high quality oscillator will have a one second frequency stable to a small fraction of a cycle.
		Radios like the PRC-68 family or the PRC-25 or PRC-77 or NRD-545 use some crystals and a frequency syntheizer to set the operatiing frequency and do not need to be recrystaled to change frequency.
	www.pacificsites.com /~brooke/Xtal.shtml (1245 words)

	Frequency offset estimation. (Site not responding. Last check: 2007-10-25)
		certain frequency accuracy is the inverse of that frequency accuracy.
		> certain frequency accuracy is the inverse of that frequency accuracy.
		frequency is the count divided by the interval.
	www.dsprelated.com /showmessage/8026/1.php (6928 words)

	New Product Release: NEW DIGITALLY CONTROLLED TCXO PROVIDES ±1ppm ACCURACY, ±6ppm PULLABILITY, AND ...
		The device is factory calibrated to maintain an oscillator frequency accuracy to within ±1ppm over the industrial temperature range (-40°C to +85°C).
		The oscillator frequency is digitally tunable and has a push-pull range of ±6ppm.
		In addition to the frequency control options, the DS4000 features an on-board digital-temperature sensor with an accuracy of ±3°C. The temperature sensor's primary purpose is to maintain frequency accuracy over the full -40°C to +85°C range.
	www.maxim-ic.com /view_press_release.cfm?release_id=654 (297 words)

	Tektronix: Products > Wireless Communication Analyzers - WCA230A * WCA280A: Characteristics/Specs
		Frequency Range - DC to 20 MHz (Baseband), 15 MHz to 3 GHz or 8 GHz
		Signal frequency: 824 to 960 MHz or 1750 to 2170 MHz Signal power: 0 dBm to -50 dBm After Auto Level is performed at 10 MHz span.
		Signal frequency: 824 to 960 MHz or 1750 to 2170 MHz Signal power: 0 dBm to -30 dBm After Auto Level is performed at 10 MHz span, 0 dBm input.
	www.tek.com /site/ps/0,,37-16437-SPECS_EN,00.html (1536 words)

Try your search on: Qwika (all wikis)