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Television broadcasting - channel system standards
Many different channel systems are in use throughout the world, and vary per country.
A channel number represents a frequency. To the average person, a channel is represented
with a number (channel 2, channel 5, etc.). To a television set, a channel number is actually
a frequency. One way channel systems differ is in the amount of space between channels.
Other differences include the number of lines per screen and sound offset.
There are four distinct broadcast bands in television: VHF, UHF, KU-Band and C-Band.
VHF (Very High Frequency) is the original broadcast band and consists of the lower numbered
channels. UHF (Ultra High Frequency) is an extension of broadcasting channels using a
higher range of frequencies. The C-band is used for satellite broadcasting using frequencies
in the 4GHz range and the KU-band is also used for satellite broadcasting using frequencies
in the 11GHz range.
Channel systems have almost no dependence on audio, video or subtitling systems,
but most are defined to a specific broadcast band.
Exemptions to dependencies include the channel system M which is always used with NTSC.
Other channel systems are used in certain areas of the world. For example
channel system K and K' are used only by France and its territories. Russia and many former
Eastern Block countries use both D and K systems. Many countries use two different channel systems.
The first one listed applies to VHF channels, while the second applies to UHF channels.
The chart below gives some technical aspects of each different channel system.
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CHANNEL SYSTEM TECHNICAL ASPECTS
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| System |
# / Frames |
# / Lines |
Freq. Band |
Channel
Width |
Vision Width |
Sound
Offset |
Vision
Modulation |
Sound
Modulation |
In Use? |
| A |
25 |
405 |
VHF |
. |
. |
-3.5 |
Pos. |
. |
No |
| B |
25 |
625 |
VHF |
7.0 |
5.0 |
+5.5 |
Neg. |
FM |
Yes |
| C |
25 |
625 |
VHF |
. |
. |
+5.5 |
Pos. |
FM |
Yes |
| D |
25 |
625 |
VHF |
8.0 |
6.0 |
+6.5 |
Neg. |
FM |
Yes |
| E |
25 |
819 |
VHF |
. |
. |
+11 |
Neg. |
. |
No |
| F |
25 |
819 |
VHF |
. |
. |
+5.5 |
Pos. |
. |
No |
| G |
25 |
625 |
UHF |
8.0 |
5.0 |
+5.5 |
Neg. |
FM |
Yes |
| H |
25 |
625 |
UHF |
7.0 |
5.0 |
+5.5 |
Neg. |
FM |
Yes |
| I |
25 |
625 |
UHF |
8.0 |
5.5 |
+6.0 |
Neg. |
FM |
Yes |
| K |
25 |
625 |
UHF |
8.0 |
6.0 |
+6.5 |
Neg. |
FM |
Yes |
| K' |
25 |
625 |
UHF |
8.0 |
6.0 |
+6.5 |
Neg. |
FM |
Yes |
| L |
25 |
625 |
UHF |
8.0 |
6.0 |
+6.5 |
Pos. |
AM |
Yes |
| M |
30 |
525 |
both |
6.0 |
4.2 |
+4.5 |
Neg. |
FM |
Yes |
| N |
25 |
625 |
both |
6.0 |
4.2 |
+4.5 |
Neg. |
FM |
Yes |
| C- |
varies |
varies |
11GHz |
. |
. |
+6.5 |
Pos. |
FM |
Yes |
| Ku- |
varies |
varies |
11GHz |
. |
. |
+6.5 |
Neg. |
FM |
Yes |
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frames |
lines |
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MHz |
MHz |
MHz |
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