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	High frequency - Wikipedia, the free encyclopedia
		The high frequency band is very popular with amateur radio operators, who can take advantage of direct, long-distance (often inter-continental) communications and the "thrill factor" resulting from making contacts in variable conditions.
		International shortwave broadcasting utilizes this set of frequencies, as well as a seemingly declining number of "utility" users (marine, aviation, military, and diplomatic interests), who have, in recent years, been swayed over to less volatile means of communication (for example, via satellites), but may maintain HF stations after switch-over for back-up purposes.
		This is due to the frequencies on which BPL operates (typically corresponding with the HF band) and the tendency for the BPL "signal" to leak from power lines.
	en.wikipedia.org /wiki/High_frequency (295 words)

	HF Radiation - Choosing the right frequency (Site not responding. Last check: 2007-10-21)
		The MUF is proportional to the critical frequency and the secant (equal to 1/cosine) of the incident angle.
		Therefore the MUF is higher with a higher critical frequency and with a larger angle from vertical.
		For horizontal transmissions, the equivalent parameter is the maximum usable frequency (MUF).
	www.weather.nps.navy.mil /~psguest/EMEO_online/module3/module_3_2b.html (3108 words)

	HFRadio.org - Propagation - Maximum Usable Frequency, MUF Basics - high frequency radio (Site not responding. Last check: 2007-10-21)
		The amount of radio wave bending depends on the extent of penetration (which is a function of frequency), the angle of incidence, polarization of the wave, and ionospheric conditions, such as the ionization density.
		The Lowest Usable Frequency (LUF) is that frequency in the HF band at which the received field intensity is sufficient to provide the required signal-to-noise ratio for a specified time period, e.g., 0100 to 0200 UTC, on 90% of the undisturbed days of the month.
		Frequency of Optimum Transmission (FOT): In the transmission of radio waves via ionospheric reflection, the FOT is the highest effective frequency (or best working frequency) for a given path that is predicted to be usable for a specified time for a percentage of the days of the month.
	www.hfradio.org /muf_basics.html (891 words)

	Maximum Usable Angle (Site not responding. Last check: 2007-10-21)
		Maximum usable frequency is important for determining the best HF frequency to use in communicating between two locations, for example between Los Angles and Denver.
		Maximum usable frequency is still important to amateur radio operators interested in scheduling contacts with distant friends, communicating with a specific country, and in operating regional ARES/RACES HF emergency communication circuits.
		Maximum usable angle is derived by solving the maximum usable frequency equation for A. Thus the maximum usable angle is equal to:
	www.cvarc.org /tech/maxusableangle.html (2026 words)

	Maximum usable frequency (Site not responding. Last check: 2007-10-21)
		Maximum Cards Maximum Card is a Postage Stamp, Picture Postcard and Cancellation (Postmark), with Maximum Concordance between elements.
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	www.serebella.com /encyclopedia/article-Maximum_usable_frequency.html (459 words)

	Frequency selection considerations
		This frequency is known as the MAXIMUM USABLE FREQUENCY (muf).
		Likewise, atmospheric noise is greater at lower frequencies; thus, a low-frequency radio wave may have an unacceptable signal-to-noise ratio.
		Neither the muf nor the luf is a practical operating frequency.
	www.tpub.com /neets/book10/40i.htm (754 words)

	HF Propagation
		The highest frequency which may be used for reliable HF communications is known as the Maximum Usable Frequency (MUF).
		This layer reaches maximum ionization when the sun is at its highest point in the sky and this layer is also responsible the complete absorption of sky waves from the 80m and 160m amateur bands as well as the AM broadcast band during the daytime hours.
		The maximum ionization of the F2-layer is usually reached one hour after sunrise and it typically remains at this level until shortly after sunset.
	www.geocities.com /w5dxs/propagation.htm (3981 words)

	Ionospheric perturbations
		The MUF represents the statistical frequency during which a 3000 km-single hop refraction via the F2-layer is generally open 50% of the time.
		The MUF is used to define the uppermost frequency that is reflected by the F-layer at a distance of 3000 km from the transmitter.
		As there is no predicting chart for a frequency according to the altitude of shortwaves, amateurs can only estimate their chance to work (or to listen to) a far station in using the MUF or FOT and checking ionosondes charts like the one displayed at right that gives the status of the ionospheric layers.
	www.astrosurf.org /lombry/qsl-perturbation6.htm (2331 words)

	Basics of Radio Wave Propagation (Site not responding. Last check: 2007-10-21)
		It is the locus of those locations of the maximum occurrence of auroras and widens to both higher and lower latitudes during the expansion phase of a magnetic substorm.
		The maximum ordinary mode radiowave frequency capable of vertical reflection from the sporadic E layer of the ionosphere.
		The altitude of maximum proton density is near 16 000-20 000 km.
	ecjones.org /propag.html (16958 words)

	Hamquick Technician Class Tutorials
		The maximum usable frequency is a term used to describe the highest frequency that can be bounced off of the ionosphere at a particular time.
		Because most High Frequency signals generally cannot bounce off of the atmosphere, a higher maximum usable frequency means these HF frequencies on the HF bands will also be reflected.
		It is most often weak, faint, and distorted, coming in on a frequency very close to the maximum usable frequency.
	www.hamquick.com /tutorial_index.php?id=18 (619 words)

	ScienceMaster - Physical Science - Glossary of Science Terms
		The factor that relates the vertical critical frequency to the MUF for an HF circuit.
		The maximum frequency of internal oscillation of a plasma.
		The T index is an indicator of the critical frequency (foF2) of the ionosphere which determines the maximum usable frequencies for HF communication circuits.
	www.sciencemaster.com /physical/item/solar_glossary.php (3333 words)

	Radio-Electronics.Com :: Critical Frequency, LUF, and MUF (Site not responding. Last check: 2007-10-21)
		As the frequency is increased a point is reached where the signal will pass right through the layer, and on to the next one, or into outer space.
		As the frequency of a transmission is reduced further reflections from the ionosphere may be needed, and the losses from the D layer increase.
		However it should be remembered that the MUF will change significantly according to the time of day, and there fore it will be necessary alter the frequency periodically to take account of this.
	www.radio-electronics.com /info/propagation/HF/critical.php (930 words)

	MAXIMUM USABLE FREQUENCY
		MUF classique (classical maximum usable frequency, classical maximum useable frequency), JF (classical maximum usable frequency, classical maximum useable frequency), fréquence de jonction (classical maximum usable frequency, classical maximum useable frequency).
		MUF clássica (classical maximum usable frequency, classical MUF, junction frequency), JF (classical maximum usable frequency, classical MUF, junction frequency), frequência de junção (classical maximum usable frequency, classical MUF, junction frequency).
		MUF clásica (classical maximum usable frequency, classical maximum useable frequency, classical MUF, junction frequency, the frequency at which the high-and low-angle rays merge into a single ray), JF (classical maximum usable frequency, classical MUF, junction frequency), frecuencia de conjunción (classical maximum usable frequency, classical MUF, junction frequency).
	www.websters-online-dictionary.org /ma/maximum+usable+frequency.html (427 words)

	Crystal and frequency control glossary - M (Site not responding. Last check: 2007-10-21)
		In radio transmission using reflection from the regular ionized layers of the ionosphere, the upper frequency limit that can be used for transmission between two points at a specified time.
		A frequency specified as "10.0 MHz" would be understood as being a frequency of 10,000,000 Hertz (cycles per second).
		A crystal may operate at its fundamental frequency of 10 MHz, or at odd harmonics of approximately 30MHz (Third Overtone), 50MHz (Fifth Overtone), and 70 MHz (Seventh Overtone).
	www.icmfg.com /crystalglossarym.html (773 words)

	Frequency Domain Filtering
		According to discrete sampling theory, the maximum usable frequency is 0.5 cycles per pixel because at least two pixels are required to define the one cycle of the wave.
		This frequency is called the "Nyquist Frequency" (0.5 cycles/pixel) and is the highest frequency (of intensity variation) that can be accurately reproduced in our data.
		If the Nyquest frequency is given in cycles/cm then it will vary for different pixel sizes.
	www.uab.edu /radiography/Nmt422/Frequency_Domain_Filtering.htm (414 words)

	CLASSICAL MAXIMUM USABLE FREQUENCY
		The highest frequency that can be propagated in a particular mode between specified terminals by ionospheric refraction alone.
		MUF clássica (classical MUF, junction frequency), JF (classical MUF, junction frequency), frequência de junção (classical MUF, junction frequency).
		MUF clásica (classical maximum useable frequency, classical MUF, junction frequency, the frequency at which the high-and low-angle rays merge into a single ray), JF (classical MUF, junction frequency), frecuencia de conjunción (classical MUF, junction frequency).
	www.websters-online-dictionary.org /cl/classical+maximum+usable+frequency.html (218 words)

	High Frequency Radio Research (Site not responding. Last check: 2007-10-21)
		High frequency radio (commonly known as short wave radio) is a means of communication in which a radio wave signal is transmitted from one point to the ionosphere, where it is reflected back down to another point on earth.
		The term "high frequency" refers to the number of radio waves transmitted per second, and simply serves to distinguish this type of system from those which transmit at higher or lower frequencies.
		The optimum working frequency and lowest usable frequency, based on these, are displayed on the computer monitor and could also be printed.
	friendsofcrc.ca /PropagationResearch/hfpropag.html (1360 words)

	MITRE - Y2K - Geomagnetic and Ionospheric Storms and Their Possible Impacts
		Frequencies below a "Maximum Usable Frequency (MUF)" are bent back toward the Earth, while those above the MUF do not encounter sufficient bending and pass through the ionosphere into space.
		The lower the frequency, the greater the degree of signal absorption.
		During early afternoon, incoming photoionizing solar radiation is at a maximum, so the D- and F-layers are strong and the LUF and MUF are elevated.
	www.mitre.org /tech/y2k/docs/IONOSPHERIC_STORMS.html (741 words)

	Radio propagation through the ionosphere layers (Site not responding. Last check: 2007-10-21)
		It’s important to say that the power of transmission may be reduced if the radio operator knows the correct frequency and hour to operation using different layers.
		This knowledge may to stabilish the relationships between radio propagation and frequencies used in communications on the earth.
		But the radio transmissions with high frequencies may to escape easily from ionosphere to free space at periods with low ionization average.
	www.geocities.com /electricaltechnology/papers/radiopro.html (1224 words)

	[No title] (Site not responding. Last check: 2007-10-21)
		Satgen 513 Sunspots are Coming P2 by GM4IHJ (BID SGEN513) 1999-01-23 Despite a reduction in Maximum Usable Frequency for HF propagation, of late there has been a marked increase in polar auroral activity, over and slightly north of Scotland.
		A pattern which starts high in frequency and dopplers steadily down for about 20 seconds, before jumping back abruptly, to the original higher frequency, and begining to repeat the same pattern.
		It is perhaps noteworthy that this pattern, new to this author, appears at a time when the Harang Discontinuity in the auroral circulation current is passing north of the listening station.
	www.amsat.org /amsat/ftp/articles/satgen/sgen513.txt (472 words)

	M(3000)F2, the maximum usable frequency factor. (Site not responding. Last check: 2007-10-21)
		M(3000)F2 is defined as the ratio of the maximum usable frequency at a distance of 3000 km to the F2 layer critical frequency, foF2.
		This parameter represents the optimum frequency at which to broadcast a signal that is to be received at a distance of 3000 km.
		Since the value calculated is sensitive to the shape of the ionogram trace as the curve approaches the F2 critical frequency, an automated calculation is likely to be much more sensitive to small changes in the gradient of the curve.
	www.wdc.rl.ac.uk /ionosondes/resultsc.html (482 words)

	Kangaroo Tabor Software - GeoAlert-Extreme Wizard, HamTools for Amateur Radio Operators
		Normally, an estimate of the frequencies expected to have efficient ionospheric support 90 percent of the time, FOT, and those having efficient ionospheric support 50 percent of the time, MUF, are adequate estimates of upper frequency limits for planning.
		The maximum usable frequency (MUF) calculations are a description of the state of the ionosphere between two locations on the earth and not a statement on the actual performance of any operational communications circuit.
		The reason is, the MUF calculations do not include any "system parameters", such as antenna, or transmit power or man-made noise at the receiver location.
	www.taborsoft.com /gawiz (640 words)

	Owning the weather in 2025 - Military Applications of Weather Modification (appendix) (Site not responding. Last check: 2007-10-21)
		The interaction of the ionosphere on impinging electromagnetic radiation depends on the properties of the ionospheric layer, the geometry of transmission, and the frequency of the radiation.
		This range, between the maximum usable frequency (MUF) and the lowest usable frequency (LUF), is where radio waves are reflected and refracted by the ionosphere much as a partial mirror may reflect or refract visible light.
		At these higher frequencies, radio waves propagate through the ionosphere with only a small fraction of the wave scattering back in a pattern analogous to a sky wave.
	www.abovetopsecret.com /pages/af2025ap.html (1005 words)

	Changes in Ionospheric Structure
		He presented scaling arguments that suggested that the cooling and associated composition changes could lower the E- and F2-layer peaks in the ionosphere by about 2 km and 20 km respectively, but that the predicted changes in the E- and F2-layer peak electron densities would be small.
		He also showed that changes in the ``maximum usable frequency'' for radio propagation would also be small for the trace gas doubling scenario.
		The change in the height of the F2-layer and the change in critical frequency of the F2-layer between the two cases were also calculated.
	www.agu.org /revgeophys/roble01/node3.html (911 words)

	Maximum Usable Frequency Encyclopedia Article, Definition, History, Biography (Site not responding. Last check: 2007-10-21)
		Maximum Usable Frequency Encyclopedia Article, Definition, History, Biography
		Looking For maximum usable frequency - Find maximum usable frequency and more at Lycos Search.
		Find maximum usable frequency - Your relevant result is a click away!
	www.quiltplace.com /search/encyclopedia/Maximum_usable_frequency (319 words)

	Near-Real-Time MUF Map
		This is a highly informative map that can be used by amateur and professional radio communicators to determine maximum usable frequencies for any world-wide path at the indicated UTC (Zulu) time.
		The MUF for any 3,000 kilometer path can be determined by finding the midpoint (or half-way point) of the path and examining the MUF at that midpoint on the map by finding the labelled MUF contour value.
		The MUF for the given 4,000 km path is then determined at the midpoint of the desired path.
	www.spacew.com /www/realtime.php (743 words)

	Frequency switching with 3 receivers possible (Site not responding. Last check: 2007-10-21)
		In Newsletter No. 19 (January 1995) we reported on the availability of the frequency switching observing mode at the 30m telescope.
		However, the observer should be aware of a possible problem with the 3 receiver configuration: baselines may be worse than when using only the 3 mm or/and 1.3 mm 230G1 receivers.
		Maximum usable frequency throw (in velocity units): 45 km/sec
	iram.fr /IRAMFR/ARN/jul95/node5.html (232 words)

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