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High Frequency
Propagation characteristics
Since the ionosphere often refract HF radio waves quite well (a phenomenon known as reflected wave propagation), this range is widely used for radio communication medium range and long term. However, the appropriateness of this portion of the spectrum for communication varies greatly with a complex combination of factors:
Sunlight / darkness in the place of transmission and reception
Transmitter / proximity receiver terminator
Season
Sunspot cycle
Solar activity
Polar Aurora
These and other factors contribute, at each point in time for a given communication path, a
Maximum usable frequency (MUF)
Lowest usable frequency (LUF) and
Frequency optimum transmission (FOT)
The exploitation of, and the limits imposed by these characteristics
When all factors are in communication optimal worldwide is available on the IC. On many other occasions, you may contact across and between continents and oceans. At worst, when a band is "dead", no communication beyond the limited ground wave paths possible, no matter what powers, antennas and other technologies are brought to endure. When a transcontinental route or around the world is open at a given frequency, digital SSB, CW and communication is possible through the transfer of power surprisingly low, often the order of tens of watts, provided suitable antennas are in use at both ends and there is interference by natural or man-little or nothing. In a as open band, interference originating over a wide area affects many potential users. These issues are important for military, security and radio users amateur HF bands.
Applications
A modern M700PRO Icom two-way radio for marine HF radio communications.
The high frequency band is very popular amateur radio operators, who can take advantage of direct, long distance (often intercontinental) communications and the "thrill factor" resulting able to network variables. International shortwave broadcasting utilizes this set of frequencies as well as an apparently declining number of "utility" users (marine, aviation, military and diplomatic interests), they have, in recent years, staggered to less volatile means of communication (Eg via satellite), but you can keep HF stations after switch backup purposes. However, the development of technology Linking automatic based on MIL-STD-188-141A and MIL-STD-188-141B for automatic connection and frequency selection, along with high the cost of using satellites, have led to a renaissance in the use of FC in these communities. The development of high-speed modems such as those conforming to MIL-STD-188-110B to support speeds of up to 9600 bits / s also increased the ability to use HF data communications. the development of other standards such as STANAG 5066 provides for communications error-free data through the use of ARQ protocols.
CB radios operate in the top of the range (around 27 MHz), as well as study some of the links radio-transmitter (STL). Some modes of communication such as continuous wave morse code transmissions (especially by amateur radio operators) and only transmissions side band voice are more common in the HF range than other frequencies, due to their bandwidth conservation of nature, but the modes of broadband, such as transmissions television, are generally prohibited by HF relatively small piece of space in the electromagnetic spectrum.
Noise, interference, especially man-made electronic devices tend to have a great effect on the HF bands. In recent years, concerns have increased among users of certain 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 to the HF band) and the tendency for the BPL "signal" to get away from power lines. Some BPL providers have installed "notch filters" to block certain parts of the spectrum (ie the amateur bands), but a great deal of controversy on the implementation of this access method remains.
Some radio frequency identification (RFID) use IC. These labels are commonly known as HFID or HighFID of (high-frequency identification).
See also
Low frequency
High Frequency Internet Protocol
AM Radio
High Frequency Active Auroral Research Program
Next month
Space weather
References
^ Paul Harden (2005). "The activity solar and HF propagation. "QRP Amateur Radio Club International. http://www.qrparci.org/content/view/58/118/. Retrieved on 02/22/2009.
^ "Radio Amateur emergency communications. "American Radio Relay League, Inc.. 2008. Http://www.arrl.org/pio/emergen1.html. Retrieved on 02/22/2009.
Read more
Maslin, NM "HF Communications - A Systems Approach." ISBN 0-273-02675-5, Taylor & Francis Ltd., 1987
Johnson, EA, et al. "Advanced of high frequency radio communications. "ISBN 0-89006-815-1, Artech House, 1997
Narayanamurti V., et al, "Selective transmission of high frequency phonons by a superlattice: The ". Dielectric" Phonon Filter ". Phys. Rev. Lett. 43, 20,122,016 (Number 27 December 31, 1979).
Boulos Bejjani, Paul et al., "Transient acute depression induced by high frequency stimulation of deep brain." New England Journal of Medicine, Volume 340:1476-1480, 13 May 1999 Issue 19. Massachusetts Medical Society.
HC Liu, "Analytical model of high frequency resonant tunneling: The first order current response alternative. "Phys. Rev. B 43, 1253812548 (Number 15 May 15, 1991).
Sipila, M., et al. "High frequency periodic waveform time-domain system of measurement. "IEEE Transactions on Microwave Theory and Techniques, Volume 36, Number 10, pg. 1397-1405, October 1988. ISSN 0018-9480 DOI 10.1109/22.6087 INSPEC 3291255
Morshed, A., et al., "A high frequency transformer model for the" EMTP. IEEE Transactions on Power Delivery, Volume 8, Number 3, pg. 1615-1626, July 1993. ISSN 0885-8977 DOI 10.1109/61.252688 INSPEC 4,581,865
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 Recommendations. DC Smith Consultants, Los Gatos, CA.
Propagation models of HF, its.bldrdoc.gov.
High frequency wave propagation, cscamm.umd.edu.
"Grounding for high frequency circuits and low "(PDF)
"The high-frequency noise" (PDF)
"Benefits of Radio HF" Codan
vd e
Time signal stations
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Spectrum
ELF
3 Hz
30 Hz
SLF
30 Hz
300 Hz
ULF
300 Hz
3 kHz
VLF
3 kHz
30 kHz
LF
30 kHz
300 kHz
MF
300 kHz
3 MHz
HF
3 MHz
30 MHz
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30 MHz
300 MHz
UHF
300 MHz
3 GHz
SHF
3 GHz
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300 GHz
EV
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Radio
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Wavelength types
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