For continuation of the TV part of the discussion started in this thread.

Here's a very brief and somewhat simplified outline of the basic difference between NTSC, PAL, and SECAM.

All three systems work by deriving color difference signals for transmission. The overall luminance signal is called Y, so the color difference signals are R-Y, B-Y, and G-Y. In all three systems only the red and blue color diff. signals are transmitted (G-Y can be reconstructed at the receiver from R-Y, B-Y, and Y).

Both NTSC and PAL use a principle called quadrature modulation, which is basically a way of putting two distinct signals on one carrier by making sure that there is a 90-degree phase difference between them. NTSC puts each signal "as is" onto the color sub-carrier (to be accurate, they are actually both phase shifted a little to get NTSC's I and Q signals, but let's not get into that!).

Somebody mentioned earlier that PAL was designed as an improved version of NTSC. In simple terms, that's true. PAL uses the same basic modulation principle as NTSC (although without the I/Q phase shifting). The PAL signals after adjustment are called U and V. Where PAL adds its twist is that the V signal is phase inverted on every other line. (Hence the name PAL = Phase Alternation by Line.)

The 180-degree phase difference on alternate lines means that any phase error which causes a shift in color on one line will cause a shift in the other direction on the next line. The errors cancel out on the screen, or in a delay line, as I mentioned in an earlier post.

SECAM works on a different concept which doesn't involve quadrature modulation. In SECAM, the R-Y signal is transmitted on one line and the B-Y signal is transmitted on the next. A delay line stores each signal in turn, so that when a line with the R-Y signal is being transmitted, the receiver gets B-Y from the delay line (i.e. from the previous line), and vice versa. The delay line acts like a memory. Sequential Color To Memory -- Get it?

Between the systems, Paul?,
Which gives the best picture?, or is it a situation of each to their own?.

I notice most of europe uses "Western European" or "Eastern European" channel system.

Ireland uses "Irish"
Italy uses "Italian"
and UK uses "British"

amazing how the same countries always seem to do it their own way!

BS 1363 and the italian plug!

I also notice that the Irish plug type specified is "A" (Europlug). I think that's something to do with our TV system too though. Irish TVs have to ship with UHF and VHF & cable ready hyperband tuners as most of the country uses wide band cable for analogue tv and RTE uses PAL I (PalPlus widescreen & Nicam digital stereo) on a mix of UHF and VHF to broadcast RTE 1, Network 2, TV3 and TG4. Apparently VHF still gives better overall coverage in very hilly and mountanous areas (e.g. South west of ireland). RTE have been switching off VHF transmitters and adding extra UHF stations though to make frequencies available for DTT (Digital TV) and Digital Radio.

Yes, even though many countries throughout Western Europe use the 625-line PAL standard, there are still quite a few variations of it. As I mentioned before, the vision/sound spacing is 5.5MHz in system B (West), 6.5MHz in system D (East), and 6MHz in system I (UK/Ireland). Other differences include the overall video bandwidth, bandwidth of the vestigial sideband, and so on.

Channel allocations are another matter entirely. UHF allocations are the same thoughout Europe, although the sound carrier frequencies vary because of the spacing mentioned above. For VHF, most of Western Europe uses a common set of channels. That includes Germany, Austria, Switzerland, Netherlands, Sweden, Norway, Spain, etc. France went its own way as usual, with its 819-line system and unique channels, and as you noted, Italy adopted its own channels, identified with letters rather than numbers.

Similarly, most of Eastern Europe uses a common set of (different) channels, the OIRT allocation referred to in an earlier post.

Britain's VHF used its own channels 1 through 13, but broadcasts were to a different standard entirely - The old 405-line monochrome network (system A), which was finally shut down in 1985.

The allocation of VHF channels in the Republic of Ireland is more complex because there were two sets of channels sharing the same spectrum.

TV broadcasting didn't start in Ireland until the end of 1961. By that time, most countries in Europe, including Ireland, had decided that they would all ultimately adopt the 625-line standard.

However, many people in the RoI were already receiving British transmissions from across the border using imported 405-line receivers. So to keep them happy, Telefis Eireann (later RTE) opened 405-line transmitters to serve those areas where TV receivers were already in use (north & east), while going straight to 625 in other areas (e.g. the southwest). The 405-line transmitters, quite naturally, followed the British channel numbering 1 through 13, while the 625-line service was allocated the unique Irish channels A through J, which you still use today.


[This message has been edited by pauluk (edited 01-15-2003).]

Trumpy,
Each of the systems has various merits and drawbacks. You also have to look at the combinations used, for example throughout almost all of the world the PAL color system is coupled with 625-lines and the NTSC color system is used with 525-lines. The inherent difference in resolution between 525 and 625 can't really be attributed to the difference between NTSC and PAL, of course (and there are one or two exceptions to the PAL-625/NTSC-525 rule).

As I mentioned before, NTSC vertical color resolution is better than that of PAL or SECAM, even with its fewer lines to start with. On the other hand, PAL and SECAM survive phase errors much more happily and don't need the phase angle adjusted with a separate hue control.

Whatever the technical specifications, given a good signal path and properly adjusted equipment all three can give an excellent picture. Once you start talking about a poor signal, be it due to multipath distortion on a broadcast signal or due to a poor cable network, the picture can degrade fast on all three.

Believe me Paul, you don't need to tell me about faults in Coaxial cables!.
I've seen the whole spectrum of them, from a simple fault caused by a bad connection at the Aerial, to a complex fault in a Multi-point MATV system, caused by the person owning the house, looping all of the points in the house together, in a Daisy-Chain fashion, to save using a splitter in the roof void,
these people always(and I mean always!) complain, when the Bill comes in for the job, to fix it all up.

[This message has been edited by Trumpy (edited 01-16-2003).]

RTE has pretty much replaced the VHF network bar in one or two areas with UHF transmission sites. It doesn't seem to be anything to do with improving quality it's simply to free VHF spectrum up for other services. TG4 and TV3 are only available on UHF.
Channels A-J are pretty much gone.

Irish cable systems use Band I, II, III and UHF though and as nearly 2/3 of the population recieves analogue tv from cable networks tvs sold here must come with Band I/II/III and UHF tuners (hyperband) otherwise you can't watch the full analogue cable service (typically about 18 channels with no decoder) As digital TV is becoming more and more common I doubt that it'll make much difference as long as a TV can accept PAL or RGB via a SCART lead.

There are also spots that use VHF transmission for RTE 1 and Net 2 so UK TV's won't necessarily work.

Are new British-market TV sets still sold with VHF tuners? I thought some of those little portable sets still came with both VHF and UHF.

What happens if you take a VHF-405 line set to RoI and try to use it with their 625 VHF system? Will it pick up something?

Thanks for that info DJK. I know the last time I had a list from RTE that they were gradually closing down the band I transmitters (channels A, B, C). If I recall correctly, the only remaining high-power band-I transmitter was Maghera (Co. Clare). I see that RTE-1 from Maghera has now been moved up to band III (ch. E).

It does indeed seem as though in many countries the VHF TV allocation is being vacated more for government money-grabbing purposes than for real technical reasons. In the U.K. the govt. is now pressing for a move toward digital TV as fast as possible so that the spare UHF channels used only by analog at the moment can be auctioned off for yet more mobile phone usage. If that goes ahead, bands IV/V will be a complete mess here.

I've run into a couple of British tourists who have taken their UK portable to Ireland and found that reception was very poor in the popular Cork/Kerry area. Turns out, of course, that they were receiving distant UHF signals (probably Cairn Hill) and hadn't realized that they needed VHF in some areas.

Sven,
Most British-market 625-only sets are sold with just a UHF tuner, as the British VHF channels were never used for anything other than the 405-line standard. A few sets incorporating VHF tuners have re-appeared in recent years, although of course most people have no use for the VHF section here. I've also seen a few models where the on-screen menus and set-up might include VHF, but there's actually no VHF tuner fitted. Some of these have the VHF tuning options supposedly locked out and undocumented in the U.K. version of the manual, but glitches in the firmware sometimes allow someone to store a VHF channel on a preset, even though it will never work.

As for taking an old 405 (system A) receiver to Ireland, it wouldn't work anymore. For a start, system A used positive video modulation and system I uses negative (like America), so you'd never be able to get anything other than a confused mass of patterns and lines on the screen.

Some of the old British dual-standard sets were designed in such a way that they could be fairly easily modified to allow 625-line operation on VHF, however. Some were intended for the few (very few) cable systems which were used many years ago, and I don't doubt that these models were also particularly popular in the Irish Republic for the reasons outlined above.

P.S. You might find this link interesting: www.irish-tv.com


[This message has been edited by pauluk (edited 01-16-2003).]

I was thinking that if you had a modern-day British PAL set that had a working VHF tuner and if you lived close enough to the Channel, you could catch the TV stations broadcast off the top of the Eiffel Tower in Paris.

Wonder if that's even possible anymore with a little bit of tinkering inside the set...if needed (and a good rooftop aerial).

Does European PAL have "Channel 1" on the dial?

American-market TV sets don't. Of course this is much easier to visualize on a conventional [real] set with physical channel selectors instead of buttons.

Like this old relic:



[This message has been edited by SvenNYC (edited 01-16-2003).]

Here in Austria we have 2 national stations and several local ones that are available on cable only. The 2 national ones are almost commercial-free (only short blocks between movies in the evening), but you have to pay for them (actually you have to pay for setting up a TV here, about 15 Euro/month, no matter if you have an antenna or not). The " national stations are ORF 1 (VHF channel 1, already answers Sven's question) and ORF 2 (UHF channel 36 IIRC). So people who only have an antenna can watch 1&2, people who want more need cable TV (ca. 150 Euro/year) or a satellite dish (cost slightly more than 1 year of cable TV). ORF 2 interferes with many video recorders that are preset to UHF 38.

I'm not sure about the rest of the world but in Ireland due to rugged landscapes most people don't recieve their TV directly from the transmitter. There are loads of smaller relay stations all over the country filling in the gaps. So you can't say that RTE 1 is on Channel I or Network 2 is on channel J etc. It varies from place to place.

Normally you'll find RTE1 and Network 2 on VHF and possibily at 2 different locations on UHF (Same for TV3 and TG4) we seem to be in the footprint of a main transmission site and 2 relays.

As for the UK television in West Cork. That area, west cork and kerry has particular problems with UHF. There are more relays operating in the region than anywhere else and for technical reasons VHF seems to give a more reliable signal in mountanous regions than UHF although that's being fixed by just doubling the number of relays. It's nearly as bad as a cellular telephone system! Although it does give excellent reception. It's possible they needed to be on a VHF Band III channel or that they were tuning into VHF with a UHF antennaa

There is also a UHF relay (technically illegal but no politician could stop them and get elected again) "south coast community television" re-broadcasting HTV Wales, BBC wales (1/2) and Channel 4 They have a large number of UHF relays around the region but tend to require a roof mounted wideband antenna and a lot of amplification to get a good signal. A portable tv wouldn't pick up much.

one scary fact. If we disconnect all the cables from our television it still receives the four main networks (RTE1, Network 2, TV3 and TG4) in good quality!

No antenna, no cables, just from coax socket in the back! I think we're being fried by UHF / VHF tranmitters!

Typically in West Cork on UHF you'll pick up RTE1, Network 2, TV3, TG4, BBC1, BBC2, HTV and Channel 4 (the last four being illegally rebroadcast)

I still have one of those "old relic" dual-standard sets sitting in my spare room!

Some models had a UHF position on the VHF turret tuner, while others had a separate changeover switch for 405 and 625. The UHF was either continuously variable, as in the set you pictured above, or came with typically 4 presets.

Re channel 1 in America, it used to exist back in the 1940s. Have a look at here .

The multitude of relay stations (transposers to left-of-ponders) in southwest Ireland is also found in parts of Britain. Over here in the east of England the landscape is relatively flat, and a few high-power transmitters provide good coverage to most areas. There are one or two low power relays, typically in the "dip" of a built-up city, but they are few. Go over to Wales (which is very hilly) and the change to UHF meant that dozens of relays had to be built to provide complete coverage.

When the VHF 405 service was closed down in 1985, there were complaints from some parts of Wales and Scotland from people who still had inadequate UHF signals.

By the way, in Britain band I (ch. 1 - 5) was used only by the BBC. When ITA (Independent TV) started in the 1950s the authorities assigned band III, although in later years some BBC stations also used band III channels.



[This message has been edited by pauluk (edited 01-17-2003).]

I checked the OIRT acronym that was mentioned earlier. It stands for Organisation Internationale de Radiodiffusion et Télévision.

Curious that an organization for Eastern European standards chose a French name, but maybe they thought it would be more widely understood.

Paul,
I have heard that the old Russia, uses PAL(B/G) signals as well, I would have thought that they would have gone with the NTSC system.
Your thoughts on this.

Why in the world should the russians have used the "enemie's" NTSC system? It's at any rate a US invention!
I'd rather have guessed they were on SECAM eastern European.

There's no way they'd have used NTSC I'm supprised that they didn't just invent their own totally incompatable system though. SECAM's almost too mainstream!

Yes, the old USSR used SECAM, systems D and K, with the OIRT channel allocations.

I'm not sure what has happened in recent years with the former Soviet Republics which broke away, such as Latvia, Estonia, etc. They may well have taken a decision to changeover to PAL.