Which do most countries outside of North America use? Or do they use both like we do?
Assuming we’re talking TV…
Australia: Both. Primarily VHF (for now).
There are three TV broadcast bands: lower VHF (ch 2-6, 54 -82 Mhz), upper VHF (ch 7 - 13, 174 - 210 Mhz) and UHF (ch 14 -83, 470 - 884 Mhz).
AFAIK, in Europe, and I assume elsewhere, they are used pretty much the same as in the USA: Transmissions started in lower VHF and later some stations have started higher up.
And is this the same whether the country in question uses PAL, SECAM, or NTSC?
That information is from the US but I believe the bands are the same in Europe and possibly most of the world. It may not be the case and it is not as starightforward as it seems at first sight, not because of different color systems you have mentioned but because of different bandwidths.
http://www.ee.surrey.ac.uk/Contrib/WorldTV/broadcast.html shows TV systems used by countries. You can see for example that Germany uses PAL-I while Italy uses PAL-B which differ in the bandwidth used so it is probable that the assignment of channels is not the same in both countries but I cannot confirm this as I cannot find the information. In general though I would expect the bands to be roughly similar. Countries tend to standardrise these things internationally, at least in large regions.
Note also that we are talking broadcast channels because cable have their own set of channels with no need to leave gaps between bands.
I’ll see if I can find further information on this
PAL, SECAM, and NTSC are encoding methods. They have nothing to do with what frequency band is used to transmit the signal.
Even where the frequency is the same, there can still be differences. For example, I was taught that in the UK, VHF television signals are vertically polarized, and in the USA, they are horizontally polarized. UHF broadcasts are always circularly polarized in practice, as far as I know.
In Australia, we started out with TV being exclusively on the VHF band. Even when FM radio was starting to become significant in the USA, we still had authorities here who had decided that FM broadcasting was just a passing idea.
Unfortunately for them, their short-sightedness became apparent when FM radio was introduced about twentyfive years ago. Suddenly there was much conflict and interference of signal between TV and radio.
This saw a large scale migration of many regional services away from the low VHF band to UHF, which then had its own consequences of forcing many people into upgrading all aspects of their TV system. While there are still many high band VHF services happily running as they have done for years, all new free-to-air services are new exclusively UHF.
In the UK most VHF radio transmissions are circulary polarized. UHF television is mostly horizontaly polarized but some low power (infill) transmitters are vertically polarized. There are no longer any VHF television transmissions in Britain.
>> There are no longer any VHF television transmissions in Britain
That is interesting. Have the VHF TV bands been reassigned or are they just empty? My guess is eventually they will be reassigned everywhere.
Yes, the VHF TV band has been reassigned to be used for (I think) for mobile radio use. The British Government is also keen to end analogue UHF transmissions (just leaving digital UHF broadcasts) the reason for this is that they can auction off this spectrum for cell-phone and other mobile comms. use. They can pick up millions of pounds in revenue this way. Target date for the analogue switch off is between 2006 and 2010.
I read that in the 60s it was decided that if the TV manufacturers wouldn’t agree to allow every set to get UHF that they would reassign each city so that some cities were strictly VHF and some UHF.
The VHF band was channels 1-13 (with Ch 1 being given back to moblie services such as taxis). Then the UHF band was 14-83 (with Ch 70-83 being given back to cellular phones). After HDTV comes in (mandated by 2006 but not expected) Ch 60-69 will be taken away from TV.
Correct me if this is wrong.
Also according to an FCC article it says that stations now broadcasting on TV and DTV can decided in 2006 to keep which channel they want. For example WGN-TV is channel 9 and DTV channel 19. It can decide then which channel to keep. Obviously channels over 60 will have to keep their DTV designation at they won’t be anymore. So in Chicago Ch 60,62 and 66 will be gone.
I also read that under todays technology the seperation of channels like channels 2 and 3 can’t occur in the same city. By one channel in VHF and six channels in UHF would not be necessary.
[Channels 6 and 7 are next to each other but really not they are seperated by High VHF and Low VHF so they are OK in one city. Also channels 4 and 5 are next to each other but for some reason don’t interfere either.]
I have a 1984 Emerson television with VHF and UHF dials. The UHF dial goes up to channel 81. If you can tune in channels 79, 80, and 81 at the right place, you can listen to phone conversations for a few seconds before the sound goes back to static.
Also, I have a Sears portable radio from the 70’s. It can tune in on the audio of the VHF channels. If you tune to the spaces between channels 10, 11, and 12, you can also hear phone conversations.