High frequency

High frequency

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). Shortwave (2.310 - 25.820 MHz) overlaps and is slightly lower than HF.

Propagation characteristics

Since the ionosphere often reflects HF radio waves quite well (a phenomenon known as skywave propagation), this range is extensively used for medium and long range radio communication. 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 terminator
*Sunspot cycle
*Solar activity
*Polar aurora
*Maximum usable frequency
*Lowest usable high frequency
*Frequency of operation within the HF range


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-188-141A and MIL-STD-188-141B for automated connectivity and frequency selection, along with the high costs of satellite usage, have led to a renaissance in HF usage among these communities. The development of higher speed modems such as those conforming to MIL-STD-188-110B which support data rates up to 9600 bit/s has also increased the usability of HF for data communications. 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 is believed to have 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.

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

ee also

*Low frequency
*High Frequency Internet Protocol
*AM radio
*High Frequency Active Auroral Research Program
*Radio propagation
*Space weather

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, " [http://www.vlf.it/frequency/bands.html Definition of frequency bands (VLF, ELF... etc.)] ". IK1QFK Home Page (vlf.it).
* Douglas C. Smith, [http://www.emcesd.com/ High Frequency Measurements Web Page; Index and Technical Tidbits] . D. C. Smith Consultants, Los Gatos, CA.
* [http://www.its.bldrdoc.gov/elbert/hf.html High Frequency Propagation Models] , its.bldrdoc.gov.
* [http://www.cscamm.umd.edu/programs/hfw05/ High Frequency Wave Propagation] , cscamm.umd.edu.
* " [http://www.analog.com/UploadedFiles/Application_Notes/698455131755584673020828AN_345.pdf Grounding for Low- and High-Frequency Circuits] " (PDF)
* " [http://www.mrec.org/pubs/HighFrequencyNoise_InformationalPage_05.pdf High frequency noise] " (PDF)
* " [http://www.codan.com.au/HFRadio/WhyHF/tabid/305/Default.aspx Advantages of HF Radio] " Codan

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Look at other dictionaries:

  • high frequency — ► NOUN ▪ (in radio) a frequency of 3 30 megahertz …   English terms dictionary

  • high frequency — n. any radio frequency between 3 and 30 megahertz …   English World dictionary

  • high frequency — high frequency, adj. the range of frequencies in the radio spectrum between 3 and 30 megahertz. [1890 95] * * * …   Universalium

  • high-frequency — ˈ ̷ ̷| ̷ ̷ ̷ ̷ ̷ ̷ adjective Etymology: high frequency 1. : occurring very frequently drills based on the repetition of high frequency words 2. : relating to high frequency: as a. : involving a radio wave of high frequency used especi …   Useful english dictionary

  • high frequency — noun Date: 1892 a radio frequency between very high frequency and medium frequency see radio frequency table …   New Collegiate Dictionary

  • high frequency — /haɪ ˈfrikwənsi / (say huy freekwuhnsee) noun 1. any radiofrequency between 3 and 30 megahertz. Abbrev.: HF 2. any audible frequency which is high in pitch. –high frequency, adjective …  

  • high-frequency — adjective Of or pertaining to high frequency sound or other radiation …   Wiktionary

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  • high frequency — aukštasis dažnis statusas T sritis Standartizacija ir metrologija apibrėžtis Dažniausiai tai elektromagnetinių virpesių dažnis nuo 10⁵ Hz iki 10¹² Hz. atitikmenys: angl. high frequency vok. Hochfrequenz, f rus. высокая частота, f pranc. haute… …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

  • high frequency — aukštasis dažnis statusas T sritis Standartizacija ir metrologija apibrėžtis Radijo dažnis nuo 3 MHz iki 300 MHz. atitikmenys: angl. high frequency vok. Hochfrequenz, f rus. высокая частота, f pranc. haute fréquence, f …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

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