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About RF Cafe
Copyright: 1996 - 2024 Web BSEE - KB3UON RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while typing up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived... All trademarks, copyrights, patents, and other rights of ownership to images
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Radio Electromagnetic Spectrum Frequency Bands |
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This chart shows the relative positions of the most common frequency bands, and is not to scale. ELF = Extremely Low Frequency VF = Voice Frequency VLF = Very Low Frequency LF = Low Frequency MF = Medium Frequency HF = High Frequency VHF = Very High Frequency UHF = Ultra High Frequency SHF = Super High Frequency EHF = Extremely High Frequency If you do a search on the origin of the designations for the various frequency bands, what you will find that nobody really knows. I have seen some pretty bogus explanations for how the band designation came to be, but I seriously doubt that the letters were assigned in order to confuse the enemy during WWII, or that "X" band was named for "cross," like in the cross hairs of precision targeting radars. There is some logic in the upper and lower frequencies of the bands, however. The "3x10n" frequencies derive from wavelength in meters. Recalling that the speed of light in air is 300,000 km/s, that means a 1 meter wavelength translates to a frequency of 300 MHz, 10 meters is 30 MHz, 100 meters is 3 MHz, etc. At some point, some wise soul decided that it was time to start over at a single digit for L-band at 1 GHz. The new regions are in octaves, except for 3 GHz, to 8 GHz. If anyone knows why 12.5, 18, and 26.5 GHz band edges were chosen, I would appreciate your letting me know. Regarding the Ku, K, and Ka bands, supposedly K was named after the German word for "short," as in shortwave - Kurz. Ku is supposedly for K-under and Ka is supposedly K-above. That, of course, is inconsistent since since the K, if is derives from Kurz in wavelength, so K-under would be a lower (lesser) wavelength (hence higher frequency) and K-above would be a longer (greater) wavelength (hence lower frequency). Mostly likely, the certain origins are buried with their progenitors.
Posted February 22, 2018 (update) |
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