405 line standard outside the UK

[Steve]

Between 1969 (duplication of BBC1 and ITV on 625) and 1985 (405 shutdown) distribution was all 625. Converters, first analogue, then digital, were used at each main transmitter site.

It always struck me as being a bit odd having a standards converter at each site given its cost. Perhaps it was still cheaper than having the converter at each regional broadcasting center and distributing it seperately?

Actually - Having just checked the network maps, each region only has 1 (some 2) main stations. Maybe when there were 2, one was relaying offair.

From 1967 (start of colour) analogue distribution was always in PAL composite. Then sound-in-syncs was added to save a separate sound channel. This puts digitally coded sound in the sync pulses. Stripped off before it goes to the transmitter.

Was sound-in-sync used to distribute just the associated TV audio, or was there spare capacity for radio feeds too? Was this the basis for NICAM?

Composite digital distribution was used, and probably still is used. AFAIK the signals going to the analogue terrestrial transmitters were and are always composite PAL, whether digitised or not. It is possible that has changed since digital terrestrial transmissions. These are inherently component and should never have seen a PAL coding process ever. It would make sense to send component signals to each main TX, then PAL code for analogue and COFDM code etc for digital.

Going back to distribution - Within the studio complex, was everything always kept component? Or is that just something that came along in the digital age?

I have read that you could resolve an 819 line picture > on a 405 set. You would get 2 half width pictures across the screen.

From what I can remember, that's correct. Back when I was about 10 there was a big sporadic-E lift and I clearly remember being able to receive, and resolve, pictures from French TV on a 405 set. The results were similar to what you described IIRC.

Tez.

[ppppenguin]

Steve

Standards converters were expensive but the Post Office/BT charged a fortune for links. I suspect it was much cheaper to convert at the TX. It was only main stations anyway, all the relays received " off air " from their parent stations.

There was no spare capacity in the SIS signal. It was upgraded to stereo when NICAM sound was introduced. I don't think the SIS was compressed but I'd have to check that.

Standard studio practice was composite throughout until the 1980s. If only because all the VTRs were composite. When Betacam became available people started to build analogue component facilities. Very expensive for switching and routing as you needed everything x3. Composite was still used very heavily until areas were rebuilt as digital. There was a limited amount of digital composite too. A large facility, such as TC, would have digital and component islands in a sea of composite analogue. Until the main routing infrastructure was rebuilt as digital. Now the moves are towards video over IP using big disk servers, gigabit ethernet, optical networking etc.

[Hybrid tellies]

Hah, For those that long for the return of the 405 line system you would soon be sorry. Yes there were advantages with bandwidth but there were other problems. First you would have to get used to that 10Khz line whistle which from some sets was quite objectionable, Second you could get good pictures on smaller screens but 20 " screens was pushing it. On 24 " screens the space between the lines was very noticable, unless of course the crt was knackered . Finally they used AM+ going video modulation which was very prone to all forms of impulsive interference ie showing up as bright white lines across the picture, this problem is reduced considerably by using AM- going modulation.
No I am afraid technology had caught up with 405 by the early 1960's. 405 should have been shut down by the mid 1970's and the VHF channels re engineered for 625 line working.
It is for the reasons I have mentioned that the rest of the world opted for 625 lines apart from France Japan and the Americas.
To give you some idea of 405/819 bandwidth. Where I used to live in Cornwall every Summer all the old BBC1 405 line channels were effected by continental interference, when the French 819 line system was crashing in it would effect 2 of our 405 line channels.
Mind you,some of the digital pictures I have seen on both Satellite and Freeview have been a good deal worse than those 405 line pictures I can remember watching. Sometimes I think we have taken a few steps forward and a dozen back

[ppppenguin]

Line whistle no longer a problem with LCDs. Or with line doubling on CRTs. This also solves the line visibility problem.

Co-channel problems are much worse on VHF, esp. band 1. Nothing to do with line standard.

Positive vision modulation is not a fundamental problem. I think it may still be used with 625 in a few countries but I'm not sure. Spot suppression circuitry gets rid of the worst of the problems. Again it was much worse when car ignition was badly suppressed and also much worse on VHF than UHF.

I've got a moderation problem here too. This topic has drifted a lot but the discussion is still interesting. Any ideas for a new topic name where we can continue this discussion. I'll put links both ways so we can follow it easily.

[oldeurope]

Hello Jeffrey,
you wrote 3x3x3x3x5 for 405 and 5x5x5x5 for 625 lines
When I modified my camera, I found an other way to
get 405 and 625 in the free run mode.
I doubled the line frequency and divided it with a
modulo counter to get a V-trigger puls.
So I get interlaced video in the free run mode at 405
and 625 lines.
Before the modifikation, V was line triggered.
look here:
www.pixum.de/viewalbum/?id=1175787
Darius

[ppppenguin]

The usual method in olden times was to start with an oscillator at 2xFh. 31250Hz for 625, 20250Hz for 405. Then divide by 2 for H and by the number of lines for V. The important point is that before transistors the usual method for making frequency dividers was locked oscillators. Usually blocking oscillators. Divide by 3 or 5 is easy. Much more than that and there is a real risk of locking to the wrong frequency. Divide by 25 could easily drift to 26 or 24.

[oldeurope]

There is a clever way for an analogue divider made
by Fortescue.
When I was young I used monoflops for dividing.
Darius

[AC/HL]

Steve asks why the French never persued 819 lines. I seem to remember reading somewhere that 819 was only transmitted from the Paris (Eiffel tower) transmitter, and that transmitter was destroyed by a fire. If true, and given the problems highlighted in this thread (possibly also lack of economies of scale, as the rest of Europe is now 625) it was probably a convenient point to quietly drop it.

[Steve]

Steve asks why the French never persued 819 lines. I seem to remember reading somewhere that 819 was only transmitted from the Paris (Eiffel tower) transmitter, and that transmitter was destroyed by a fire. If true, and given the problems highlighted in this thread (possibly also lack of economies of scale, as the rest of Europe is now 625) it was probably a convenient point to quietly drop it.

Ooh, I know the answer to this one.

You're correct about the fire and the French then dropping the standard. But this was a few years after the war and the system was the 441 line system the Germans had introduced.

Pity they didn't do the same with their Syndicat des Constructeurs d'Appareils Radiorécepteurs et Téléviseurs connector!

[Hybrid tellies]

The French 441 line system, which was similiar to our 405 line system, did come to an end when the Eiffel tower transmitter burnt out. The 819 line system then became their main system using an extensive network of vhf transmitters. The 819 line system was then closed down by the early 1980's and replaced with their present 625 line system using the same uhf channels as us. Unlike us they re engineered the vhf channels for a 625 line service called Canal Plus. This is an encrypted pay as you view service.
I hope this is of some help.
On the subject of line whistle, at work we have these new lcd vdu things and some of them are starting to emitt a rather loud and annoying whistling sound which can be heard right across our office In fact it sounds like a 9-10Khz tone!

Interesting to know that 405 line sets could easily turn up in Hong Kong, Ireland and Gibraltar, perhaps these are other places to search. Did any of these locations use Channel 1, the same as the original frequency used for the Alexandra Palace transmissions? It would be interesting to find one of the cable 405 line sets from Hong Kong.

We had a 405 only set right up until the closedown, I remember well watching the weather, then the picture of a 405 line TV set, then the BBC globe and closing announcement and then....nothing. It was very sad. My mother was furious that she had to have a new aerial and a new TV set and also pay for a colour licence!

My interest in 405 started before the closedown and, after the closedown, it was spurred on, it was some years after the shutdown though before I was able to watch anything other than pre-recorded 405 line tapes, but they were certainly better than nothing.

I was in my early teens at the time, I now cringe when I think of the few pre-war sets I pulled to pieces in my attempt to learn how they worked. They had been a a dealers shed for years and years after he retired, I got them for next to nothing and I just wish I had of really appreciated what I had got hold of before I butchered them!

Well i will always have a soft spot for 405 line and 405 line tvs i was in my teens in the last years of its life i remember our old dual standard set very well.

Even when 405 closed down it was a while before my dad got a colour set and i think that was a bush.

It was very much like my GEC colour set to look at obviously it had tr*ns*st*rs...

[Hybrid tellies]

Sadly I missed the 405 line shutdown as I was in the middle of moving and helping someone else move as well. I don't think it would have made much difference though as both Wenvoe and St Hilary 405 line transmitters were on such reduced power that where we lived just outside Bath there was hardly any signal even when the transmitters were on full power

Fableglade wrote;

(re Ireland, HK and Gibraltar)

> Did any of these locations use Channel 1, the same
> as the original frequency used for the Alexandra
> Palace transmissions? It would be interesting to find > one of the cable 405 line sets from Hong Kong.

Not sure offhand, but if someone has a World Radio & TV Handbook from the 60s or 70s chances are a full list of frequencies for those countries will be in there. Pretty sure the Republic of Ireland didn't use Channel 1; apart from the fact that the BBC's transmitter at Divis in Belfast was on Channel 1, RTE's main 405-line transmitter at Kippure operated on Channel 7 (B7, as opposed to E7) in Band III, IIRC.

Tez.

[peter_scott]

I have read that you could resolve an 819 line picture on a 405 set. You would get 2 half width pictures across the screen. Seems reasonable as the line length on 819 was almost exactly half that on 405. Can't imagine the resolution would have been too great with the limited bandwidth of a 405 set.

I can remember taking some photos of 819 line broadcasts on a 405 line set back in the 1960s. I think this is one showing a singer holding a microphone. http://www.scottpeter.pwp.blueyonder.co.uk/819.JPG
I was quite pleased at receiving the signal here in Scotland.

[Duke_Nukem]

In the Wireless and Electrical Trader mag (7th Jan 1950) they review the previous year and under " July " they have :-

" Eiffel tower television station is to change from it's present definition of 455 lines to the British 405-line system. This is decided at a conference of the International Radio Consultative Committee. "

Does anyone know if the French actually used 405-lines ? Or did they appeal against the decision ? (Or more likely just ignore it )

TTFN,
Jon

[Hybrid tellies]

Hi Jon
I don't think they did. Being French of course they saw us sticking with 405, the rest of Europe going to 625 so they decided to be different again and go to 819. Totally ignoring the IRCC of course
If I do hear any more about French 405 I will post it up.
Cheers Simon.