high frequency

• 高頻度、高周波

関

alphoid、frequent、high incidence、radio frequency、radiofrequency

WordNet

1. frequently encountered; "a frequent (or common) error is using the transitive verb `lay for the intransitive `lie";
2. be a regular or frequent visitor to a certain place; "She haunts the ballet" (同)haunt
3. coming at short intervals or habitually; "a frequent guest"; "frequent complaints"
4. 30 to 300 gigahertz (同)EHF
5. in or to a high position, amount, or degree; "prices have gone up far too high"
6. a state of altered consciousness induced by alcohol or narcotics; "they took drugs to get a high on"
7. a state of sustained elation; "Im on a permanent high these days"
8. an air mass of higher than normal pressure; "the east coast benefits from a Bermuda high"
9. a lofty level or position or degree; "summer temperatures reached an all-time high"
10. a high place; "they stood on high and observed the countryside"; "he doesnt like heights" (同)heights
11. at a great altitude; "he climbed high on the ladder" (同)high up
12. used of sounds and voices; high in pitch or frequency (同)high-pitched
13. happy and excited and energetic (同)in high spirits
14. slightly and pleasantly intoxicated from alcohol or a drug (especially marijuana) (同)mellow
15. in a rich manner; "he lives high" (同)richly, luxuriously
16. (literal meaning) being at or having a relatively great or specific elevation or upward extension (sometimes used in combinations like `knee-high'
17. far up toward the source; "he lives high up the river"
18. greater than normal in degree or intensity or amount; "a high temperature"; "a high price"; "the high point of his career"; "high risks"; "has high hopes"; "the river is high"; "he has a high opinion of himself"
19. the number of observations in a given statistical category (同)absolute frequency
20. the number of occurrences within a given time period; "the frequency of modulation was 40 cycles per second"; "the frequency of his seizures increased as he grew older" (同)frequence, oftenness
21. the ratio of the number of observations in a statistical category to the total number of observations (同)relative frequency

PrepTutorEJDIC

1. 『しばしば起こる』,頻繁な / 『常習的な』 / ‘に'『しばしば行く』,常に出入りする
2. 極超短波(周波数が3,000‐30,000メガヘルツの電波)
3. 『高い』,高い所にある / 《数の後に置いて》高さが…ある / (数量・程度などが標準より)『高い』,大きい,激しい / (身分・地位が)『高い』,高貴な / 『気高い』,高潔な / (声の調子が)『高い』,鋭い / 値段の高い,金の掛かる,ぜいたくな / 楽しい,陽気な,上得意の / (時・季節が)盛りの,たけなわの / (色が)濃い,赤い / 《話》(酒・麻薬などに)酔って / 『高く』,高い所に / (価値・程度などが)高く,高度に,激しく / 〈C〉《話》高水準,高値 / 〈U〉(自動車の)高速ギア / 〈C〉《話》(麻薬などによる)酔った状態
4. 〈U〉しばしば起こること,頻繁 / 〈C〉頻度数,(発生・生現などの)回数 / 〈C〉振動数;周波数

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/03/16 19:18:38」(JST)

wiki en

[Wiki en表示]

High frequency Frequency range 3 to 30 MHz

ITU Radio Band Numbers 1 2 3 4 5 6 7 8 9 10 11 12 ITU Radio Band Symbols ELF SLF ULF VLF LF MF HF VHF UHF SHF EHF THF NATO Radio bands A B C D E F G H I J K L M IEEE Radar bands HF VHF UHF L S C X Ku K Ka Q V W D

High frequency (HF) radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters (ten to one hundred metres). Frequencies immediately below HF are denoted medium frequency (MF), and the next higher frequencies are known as very high frequency (VHF). The HF band is a major part of the shortwave band of frequencies, so communication at these frequencies is often called shortwave radio. Because radio waves in this band can be reflected back to Earth by the ionosphere layer in the atmosphere, called "skip" or skywave propagation, these frequencies can be used for long distance communication, at intercontinental distances. The band is used by international shortwave broadcasting stations (2.310 - 25.820 MHz), aviation communication, government time stations, weather stations, amateur radio and citizens band services, among other uses.

Propagation characteristics

A modern Icom M700Pro two-way radio for marine HF radio communications.

The dominant means of long distance communication in this band is skywave (skip) propagation, in which radio waves directed at an angle into the sky reflect (actually refract) back to Earth from layers of ionized atoms in the ionosphere. By this method HF radio waves can travel beyond the horizon, around the curve of the Earth, and can be received at intercontinental distances. However, suitability of this portion of the spectrum for such communication varies greatly with a complex combination of factors:

• Sunlight/darkness at site of transmission and reception
• Transmitter/receiver proximity to solar terminator
• Season
• Sunspot cycle
• Solar activity
• Polar aurora

At any point in time, for a given "skip" communication path between two points, the frequencies at which communication is possible are specified by these parameters

• Maximum usable frequency (MUF)
• Lowest usable high frequency (LUF) and a
• Frequency of optimum transmission (FOT)

The maximum usable frequency regularly drops below 10 MHz in darkness during the winter months, while in summer during daylight it can easily surpass 30 MHz. It depends on the angle of incidence of the waves; it is lowest when the waves are directed straight upwards, and is higher with less acute angles. This means that at longer distances, where the waves graze the ionosphere at a very blunt angle, the MUF may be much higher. The lowest usable frequency depends on the absorption in the lower layer of the ionosphere (the D-layer). This absorption is stronger at low frequencies and is also stronger with increased solar activity (for example in daylight); total absorption often occurs at frequencies below 5 MHz during daytime. The result of these two factors is that the usable spectrum shifts towards the lower frequencies and into the Medium Frequency (MF) range during winter nights, while on a day in full summer the higher frequencies tend to be more usable, often into the lower VHF range.^{[citation needed]}

When all factors are at their optimum, worldwide communication is possible on HF. At many other times it is possible to make contact across and between continents or oceans. At worst, when a band is 'dead', no communication beyond the limited groundwave paths is possible no matter what powers, antennas or other technologies are brought to bear. When a transcontinental or worldwide path is open on a particular frequency, digital, SSB and Morse code communication is possible using surprisingly low transmission powers, often of the order of milliwatts, provided suitable antennas are in use at both ends and that there is little or no man-made or natural interference. On such an open band, interference originating over a wide area affects many potential users. These issues are significant to military, safety and amateur radio users of the HF bands.

Uses

An amateur radio station incorporating two HF transceivers.

The main users of the high frequency spectrum are:

• Military and governmental communication systems
• Aviation air-to-ground communications
• Amateur radio
• Shortwave international and regional broadcasting
• Maritime sea-to-shore services
• Over the horizon radar systems

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.

However, the development of Automatic Link Establishment technology based on MIL-STD-188-141 for automated connectivity and frequency selection, along with the high costs of satellite usage, have led to a renaissance in HF usage in government networks. The development of higher speed modems such as those conforming to MIL-STD-188-110C which support data rates up to 120 kilobit/s has also increased the usability of HF for data communications and video transmission. Other standards development such as STANAG 5066 provides for error free data communications through the use of ARQ protocols.

CB radios operate in the higher portion of the range (around 27 MHz), as do some studio-to-transmitter (STL) radio links. Some modes of communication, such as continuous wave morse code transmissions (especially by amateur radio operators) and single sideband voice transmissions are more common in the HF range than on other frequencies, because of their bandwidth-conserving nature, but broadband modes, such as TV transmissions, are generally prohibited by HF's relatively small chunk of electromagnetic spectrum space.

Noise, especially man-made interference from electronic devices, tends to have a great effect on the HF bands. In recent years, concerns have risen among certain users of the HF spectrum over "broadband over power lines" (BPL) Internet access, which has an almost destructive effect on HF communications. 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. Some BPL providers have installed "notch filters" to block out certain portions of the spectrum (namely the amateur radio bands), but a great amount of controversy over the deployment of this access method remains. Other electronic devices including plasma televisions can also have a detrimental effect on the HF spectrum.

In aviation, HF communication systems are required for all trans-oceanic flights. These systems incorporate frequencies down to 2 MHz to include the 2182 kHz international distress and calling channel.

Some radio frequency identification (RFID) tags utilize HF. These tags are commonly known as HFID's or HighFID's (High Frequency Identification).

See also

• High Frequency Active Auroral Research Program
• High Frequency Internet Protocol
• Low frequency
• Radio propagation
• Space weather

References

Further reading

• Maslin, N.M. "HF Communications - A Systems Approach". ISBN 0-273-02675-5, Taylor & Francis Ltd, 1987
• Johnson, E.E., et al., "Advanced High-Frequency Radio Communications". ISBN 0-89006-815-1, Artech House, 1997
• V. Narayanamurti, et al., "Selective Transmission of High-Frequency Phonons by a Superlattice: The "Dielectric" Phonon Filter". Phys. Rev. Lett. 43, 2012–2016 (Issue 27 – 31 December 1979).
• Boulos-Paul Bejjani, et al., "Transient Acute Depression Induced by High-Frequency Deep-Brain Stimulation". New England Journal of Medicine, Volume 340:1476-1480 May 13, 1999 Number 19. Massachusetts Medical Society.
• H. C. Liu, "Analytical model of high-frequency resonant tunneling: The first-order ac current response". Phys. Rev. B 43, 12538–12548 (Issue 15 – 15 May 1991).
• Sipila, M., et al., "High-frequency periodic time-domain waveform measurement system". IEEE Transactions on Microwave Theory and Techniques, Volume 36, Issue 10, pg. 1397-1405, Oct 1988. ISSN 0018-9480 INSPEC 3291255 DOI 10.1109/22.6087
• Morched, A., et al., "A high frequency transformer model for the EMTP". IEEE Transactions on Power Delivery, Volume 8, Issue 3, pg. 1615-1626, Jul 1993. ISSN 0885-8977 INSPEC 4581865 DOI 10.1109/61.252688

External links

• Tomislav Stimac, "Definition of frequency bands (VLF, ELF... etc.)". IK1QFK Home Page (vlf.it).
• Douglas C. Smith, High Frequency Measurements Web Page; Index and Technical Tidbits. D. C. Smith Consultants, Los Gatos, CA.
• High Frequency Propagation Models, its.bldrdoc.gov.
• High Frequency Wave Propagation, cscamm.umd.edu.
• "High frequency noise" (PDF)
• "Advantages of HF Radio" Codan
• Solar conditions for HF-radio

UpToDate Contents

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English Journal

• High nonlinearities in Langevin transducer: A comprehensive model.

• Guyomar D, Ducharne B, Sebald G.SourceUniversite de Lyon, INSA-Lyon, Laboratoire de Genie Electrique et Ferroelectricite, Bat. Gustave FERRIE, 8 rue de la Physique, 69621 Villeurbanne cedex, France.
• Ultrasonics.Ultrasonics.2011 Dec;51(8):1006-13. Epub 2011 Jun 12.
• The design and simulation of power transducers are difficult since piezoelectric, dielectric and elastic properties of ferroelectric materials differ from linear behavior when driven at large levels. This paper is devoted to modeling of a resonant power transducer at a high level of dynamic mechanic
• PMID 21724220

• Dual energy time reversed elastic wave propagation and nonlinear signal processing for localisation and depth-profiling of near-surface defects: A simulation study.

• Janssen EN, Abeele KV.SourceWave Propagation and Signal Processing, K.U. Leuven Campus Kortrijk, E. Sabbelaan 53, B-8500 Kortrijk, Belgium.
• Ultrasonics.Ultrasonics.2011 Dec;51(8):1036-43. Epub 2011 Jun 12.
• Nonlinear Elastic Wave Spectroscopy (NEWS) relies on the activation of defects by wave energy that propagates through the medium. In general, the response of activated defects will not scale linearly with the excitation amplitude, and the resulting nonlinear signatures can be identified and used for
• PMID 21714981

Japanese Journal

• Frequency of CD45RO+ subset in CD4+CD25high regulatory T cells associated with progression of hepatocellular carcinoma

• Takata Yoshiko,Nakamoto Yasunari,Nakada Akiko,Terashima Takeshi,Arihara Fumitaka,Kitahara Masaaki,Kakinoki Kaheita,Arai Kuniaki,Yamashita Taro,Sakai Yoshio,Yamashita Tatsuya,Mizukoshi Eishiro,Kaneko Shuichi
• Cancer Letters 307(2), 165-173, 2011-08-28
• … The purpose of this study was to assess the properties of CD4+CD25high/low/negative T cell subsets and analyze their relation with dendritic cells (DCs) in patients with hepatocellular carcinoma (HCC). … In HCC patients, the prevalence of CD45RO+ cells in CD4+CD25high T cells was increased and associated with higher frequencies of plasmacytoid DCs. …
• NAID 120003141809

• リングファンの動翼回転騒音に及ぼす後流の影響

• 佐々木 壮一,徳重 達也,鳥瀬 一貴,林 秀千人,Sasaki Soichi,Tokushige Tatsuya,Torise Ikki,Hayashi Hidechito
• 長崎大学工学部研究報告 41(77), 1-5, 2011-07
• … The blade rotating noise was assumed for the mechanism of the discrete frequency noise in the ring fan. … The overall noise level of the ring fan was decreased 3 dB than that of the propeller fan due to the discrete frequency noise in the first harmonics. … As a result of CFD analysis, it is considered that the discrete frequency noise was generated from the blade surface of the impeller by the periodic pressure fluctuation synchronizing with the blade passing frequency. …
• NAID 120003182955

Related Links

• Higher Frequency

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リンク元	「frequent」「高頻度」「alphoid」「radio frequency」「高周波」
拡張検索	「high frequency ventilation」
関連記事	「frequency」「high」

「frequent」

　　[★]

• adj.

• たびたびの、しばしばの、頻繁な、、高頻度の、頻回の、頻々たる。常習的な。よくある、ありがちな。いくつもの

Large artery diseases with concomitant artherothrombotic risk factors were more frequent in VB stroke patients with prior TNA compared to those without.(大血管疾患はTNAがなかった患者よりTNAが先行した椎骨脳底梗塞患者でよくありがちである/よく見られる)

• (脈拍が)早い

• vt.

• しばしば訪れる、～に常に出入りする。(大勢で)常に集まる、～に良くいる
• 常に～と交際する

関

alphoid、continual、continually、frequently、high frequency、high incidence、repeated

frequentness, frequented, frequenter

　 　 　 　

「高頻度」

　　[★]

英

high frequency、high incidence、frequent、alphoid

関

高周波、頻回、頻繁、アルフォイド

「alphoid」

　　[★]

• adj.

• 高頻度の

• n.

• アルフォイド

関

frequent、high frequency、high incidence

「radio frequency」

　　[★]

• 高周波

関

high frequency、radiofrequency

同

ラジオ波 RF

「高周波」

　　[★]

英

high frequency、radiofrequency、radio frequency

関

高頻度

「high frequency ventilation」

　　[★] 高頻度人工換気法 HFV

「frequency」

　　[★]

• n.

• しばしば起こること/状態。頻発、頻繁(⇔infrequency)
• 頻度。(脈拍・訪問・乗り物の運搬などの)回数
• (物理)振動数、周波数。(数学・統計)度数、頻度
• (生態)一定区画における種の個体数、頻度(特定の種がその区域の中の小区分の何パーセントに出現したかを示す数値)
• (医)頻尿(urinary frequency)

　 　 　 　

「high」

　　[★]

• adj.

• 高い、高度な

関

advanced、altitude、high degree、high level、high-grade、highly、tall