Channel grid
With channel spacing is in the radio technology , the difference of the center frequencies of two adjacent transmission channels in a frequency band designated. The required bandwidth of one of these transmission channels can be smaller, equal to or larger than the channel grid. If the channel grid is smaller than the channel bandwidth, one speaks of overlapping channels.
Long and medium and short wave broadcasting
In Europe, Asia, Africa and Australia, the channel spacing in the long and medium wave broadcast bands is 9 kHz, with the channel center frequency in kHz being divisible by 9 without a remainder. Exceptions are the two transmitters, Felsberg-Berus (program Europe 1 ), originally coordinated for 180 kHz, and the now switched off transmitter Zehlendorf ( Deutschlandradio Kultur ), which have been shifted up or down by 3 kHz to reduce mutual interference. On the American continent, the channel grid is 10 kHz, with the channel center frequency in kHz being divisible by 10 without a remainder. In the shortwave range, a 5 kHz grid is used worldwide within the broadcasting bands (channel center frequency in kHz can be divided by 5 without remainder).
Ultra-short wave volume II
In radio band II (VHF radio) a channel grid of 100 kHz is used. In some countries and in broadband cables, a channel spacing of 50 kHz is also used in isolated cases. The channels in the 300 kHz grid that were often shown on the frequency scale in receiving devices until the 1970s, beginning with channel 2 (corresponds to 87.6 MHz), have long been of no practical significance.
Television broadcasting
In Germany and Western Europe the channels are in the bands VHF band I (channels 2 to 4, 7 MHz distance) and III (channels 5 to 12, 7 MHz distance) as well as UHF band IV and V (channels 21 to 69, Distance 8 MHz). See the frequencies of the television channels .
Aeronautical radio
Until the early 1970s, the channel spacing in aeronautical radio (voice radio) was 50 kHz and was then reduced to 25 kHz. This meant a doubling of the usable channels.
For VHF radiotelephony in aeronautical radio, the range from 117.975 MHz to 137.000 MHz is specified by the International Telecommunication Union (ITU) in the radio regulations . Frequencies from 118.000 MHz to 136.975 MHz are possible for aeronautical radio applications. With the 25 kHz channel grid, there are 760 possible VHF radio frequencies. The operating mode is AM (amplitude modulation). The frequencies are published on the aerodrome maps and flight maps, applications for frequency allocation for a ground radio station can be made via the responsible state authorities, in Germany at the Federal Network Agency .
The increase in air traffic required an increase in air traffic management capacity. In order to multiply the frequencies available for aeronautical radio, the 8.33 kHz channel grid has been mandatory in European airspace since 1999 in the airspace above flight level 245 (24,500 feet = approx. 7.5 km), from 2007 from FL 195. General The new grid has been mandatory for aeronautical radio stations since January 1, 2018, and for ground radio stations from January 1, 2019.
Commercial radio
In German analog commercial radio, the channel spacing has been 12.5 kHz since July 2020 (previously 20 kHz). The 20 kHz channel grid can be used for existing radio networks until December 31, 2028 at the latest. In digital commercial radio, the channel spacing is 12.5 kHz ( DMR ) and 6.25 kHz ( dPMR ).
BOS radio
In the bad radio there is no single channel spacing:
- The 8 m band, for example, has a straight 20 kHz grid. The frequencies are therefore z. B. 34.360 MHz; 34.380 MHz; 34.400 MHz.
- In the 4 m band there is the odd 20 kHz grid with a 5 ending. z. B. 74.215 MHz; 74.235 MHz; 74.255 MHz.
- In the 2 m band, there is both the odd (channels 101–125 e.g. 165.210 MHz; 165.230 MHz; 165.250 MHz) and the even (channels 1–92 e.g. 167.560 MHz; 167.580 MHz; 167.600 MHz) ) 20 kHz grid.
- In the 70 cm band, the 12.5 kHz grid applies, i.e. 443.6000 MHz; 443.6125 MHz; 443.6250 MHz etc.
The operating mode is FM (frequency modulation).
Marine radio
There is also no uniform grid in VHF marine radio . The frequency spacing between two consecutive channel numbers is always 50 kHz, but there are sometimes two differently numbered channels on adjacent frequencies at a spacing of only 25 kHz. The operating mode is FM (frequency modulation).
Examples:
- Channel 60: 156.025 MHz
- Channel 1: 156.050 MHz
- Channel 61: 156.075 MHz
- Channel 2: 156.100 MHz
This channel allocation is historical, since the channels with higher numbers were only allocated later and inserted between the existing ones.
Amateur radio
Even in amateur radio, there is no uniform channel grid, if one is available at all. Due to the narrow-band operating modes such as CW and SSB on shortwave and the radios that are usually continuously tunable, there is no need to introduce a channel grid. You just look for a free place in the middle between two neighboring stations in order to transmit. Due to the bandwidth that a type of modulation occupies, we speak of channel in this sense when we mean the occupied frequency range. With CW this is a few 100 Hz, with SSB approx. 2.7 kHz. On higher bands, where one also works with wider types of modulation, a recommendation has become established to adhere to a “channel grid” that is dictated by the bandwidth of the type of modulation. The channel spacing in the FM range of the 10-meter band is usually 10 kHz. In the VHF range, where PLL-tuned devices are the rule, the channel spacing is dictated by the step size of the tuning. In the 2-meter band and in the 70-centimeter band , 25 kHz was traditionally defined as the channel spacing for FM devices. Due to better use of the frequencies and the capabilities of newer devices, the raster in the 2 m band has been halved to 12.5 kHz - which, however, often causes problems because the bandwidth of most devices and the hub are not adapted to the small channel spacing . In the USA and other countries, the channel spacing in the 2 m and 70 cm bands is 20 kHz. For bands that have not been used by radio amateurs for as long as the 6-meter band , an attempt is made to introduce frequency modulation 20 kHz (instead of 25 kHz) as the channel spacing , as a narrow-band operating mode 10 kHz (instead of 12.5 kHz), accordingly as with 25 / 12.5 with 5 and 2.5 kHz stroke.
Modulation types in amateur radio are:
- Short wave: usually SSB and CW, also AM and FM
- VHF 2 m, 70 cm: both FM in a channel grid, as well as SSB and CW freely tuned
AM = amplitude modulation, FM = frequency modulation, CW = continuous wave, SSB = single side band
Freenet
In the area of Freenet radio (semi-professional radio without approval and without charges with 1 W), only six frequencies are allocated with a channel grid of 12.5 kHz. The frequencies are thus: 149.0250 MHz; 149.0375 MHz; 149.0500 MHz; 149.0875 MHz; 149.100 MHz; 149.1125 MHz. Operating mode is FM (frequency modulation)
literature
- Ralf Rudersdorfer: Radio receiver compendium - understanding how it works, areas of application and international assignments, determining and interpreting parameters, optimizing receiving systems . 1st edition. Elektor International Media BV, Aachen 2010, ISBN 978-3-89576-224-6 .
- Frequency plan of the Federal Network Agency
Individual evidence
- ↑ final acts of the Regional Administrative Conference for the Planning of VHF Sound broadcasting (Region 1 and Part of Region 3) Geneva, 1984 (GE84), Annex 2 Chapter 3.2: "A uniform channel spacing of 100 kHz was adopted in principle for both monophonic and stereophonic emissions. The nominal carrier frequencies are, in principle, integral multiples of 100 kHz. "
- ↑ Institute for Radio Technology , Radio and TV Broadcasters in the Federal Republic of Germany, Wittsmoor List: VHF - CHANNEL DESIGNATIONS FREQUENCY RANGE II
- ↑ Eurocontrol: VHF 8.33 kHz
- ↑ Luftfahrt-Bundesamt: Rules for VHF aeronautical radio in the 8.33 kHz channel grid
- ^ Administrative regulation for the non-public mobile land radio (VVnömL). Retrieved July 15, 2020 .
- ↑ Frequency plan of the Federal Network Agency