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en:vhf [2019/03/22 21:50] (aktuell)
mb angelegt
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 +====== VHF =====
 +Radio spectrum frequencies above 30 MHz (above the shortwave bands) up to 300 MHz are known as **Very High Frequency**.
  
 +===== FM Broadcasting Band =====
 +FM broadcasting stations are located in the 87,5 - 108 MHz frequency range, as these signals are frequency modulated, this band is also known as "FM band", although there signals in other VHF bands and even a few shortwave signals which use frequency modulation.
 +
 +
 +In Germany, in the early years only the 87,5 - 100 MHz segment has been used for FM broadcasting stations, internationally,​ 88 - 108 MHz have been in use much earlier. ​
 +
 +In eastern europe (with exception of the GDR, the former German Democratic Republic), 65,9 - 73,1 MHz band was used, the so called OIRT band.
 +
 +In Japan, the 76 - 90 MHz range has been used for broadcasting,​ on the higher frequencies,​ television signals can be found in in Japan.
 +
 +===== Military communications =====
 +In World War II, VHF frequencies between 30 and 88,5 MHz found use for military communications,​ as frequency modulated signals suffer less from noise (sparks vom cars, motors, electric tramway and trains), they were found to be very reliable and a squelch funktion was easier to construct.
 +
 +The VHF is also used for public organisations,​ police, ambulance, firefighters - in Europe, it was illegal to monitor these signals for many years. As in Germany and Italy, even the possesion of receiver covering these frequencies was forbidden; in Switzerland it was legal to possess a set covering VHF, but it was only to be used on public broadcast bands. In case, accidentally a public service VHF stations was tunes, it was not allowed to make use of any on the information - and you should not be cought by the police with the set tunes to their operation frequency.
 +
 +===== Television ===== 
 +In the lower fraction of the VHF band, on frequencies below the FM broadcast band, in Europe, you could receive the VHF television channels 2, 3 and 4; the audio carrier 5,5 MHz above the video signal.
 +
 +On frequencies higher then the FM broadcast band, the television transmitters on channels 5 - 12 could be found in the 174 - 230 MHz frequency range; the audio carrier can also be found 5,5 MHz above the video signal. After terrestrial VHF television has been stopped in Europe, the frequencies are used for cable television and DAB (digital audio broadcasting).
 +
 +===== Air Band =====
 +After World War II, air traffic communications were moved from shortwaves to the VHF band. But in the Air Band, amplitude modulation is still used, the only service in the VHF range not using frequency modulation.
 +
 +The frequency range of 118 - 137 MHz is used for voice communications,​ initially a 50 kHz channel spacing was used, followed by a 25 kHz actually a 8,33 kHz channel spacing, so the number of available channels could be moultiplied.
 +
 +The 108 - 118 MHz range ist used by VOR (VHF Omnidirectional Radio Range) air traffic beacons. ​
en/vhf.txt · Zuletzt geändert: 2019/03/22 21:50 von mb