posted by Admin on Nov 29
High frequency
By Teddy Lim
HF Radio
High frequency (HF) radio frequencies are between 3 and 30 MHz. 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.
When all factors are at their optimum, worldwide communication is possible on HF radio. 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. 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 radio 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 radio bands. In recent years, concerns have risen among certain users of the HF radio spectrum over “broadband over power lines” (BPL) Internet access, which is believed to have an almost destructive effect on HF radio communications. Some radio frequency identification (RFID) tags utilize HF.
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