TV Prisma 91 - Belgian 625/819 automatic hybrid

[LENINGRAD T2]

In my country, in the early 1970s, radio and television stores introduced a system of reducing prices if someone delivered an old receiver. In a country with a capitalist economy, this is often practiced. Under socialism, financial considerations did not matter. Collected old tube devices were destroyed and burned en masse. Witnesses of such events speak of a mass of molten glass that flowed like volcanic lava. In this way, a huge number of components, mainly valves, was annihilated. I believe it had military significance. At that time, there were many radio amateurs who constructed transceivers. Unfortunately, a big barrier for them was the lack of parts.

I didn't know about the existence of cable television in the UK in the 60's. Was it an alternative to broadcasting over the air? What was the range? How was the network built? Were there intermediate devices - amplifiers? Were TV sets of any special design? My questions go beyond the topic of the post. Maybe someone would like to write something in a new chapter?

[Richard_FM]

If I remember correctly, many Belgian cities had cable systems, which I presume included channels from neighbouring countries. I've seen a picture of a 1970s TV with a row of about 15 channel buttons for use with such a system.

Thorn made the 1400 dual standard sets into the mid 1970s, and some of the other manufacturers made 405 / 625 line sets this late.

Thorn's last generation of 12 inch 405 line only portable sets were common to find in use up to the switch off in the mid 1980s.

[Murphyv310]

Have a watch of this video Adam
https://youtu.be/ltI09lTuGjk?si=AYoMWRzyhpRRrOD8

[Geordie McBoyne]

In the 1950s and up to the '80s as well as British Relay Wireless (BRW) the other major player in the UK cable TV business was Rediffusion Ltd. During the 405 line only era the two companies employed similar technologies for the distribution of the two 405 line TV services. Sound distribution was different, BRW sent the sound channels by RF and Rediffusion at loudspeaker levels.
Trevor will confirm if this is correct. As for Rediffusion and I guess it was some something similar with BRW both companies employed a tete-beche system, that is, the BBC TV vision carrier was 4.95Mhz with the video content on the upper sideband and the ITV vision carrier was 8.45Mhz with the video in the lower sideband. Transmission by balanced feeders to reject cross-talk.
Everything was fine until BBC2 came along in the mid-sixties which resulted a great deal of re-engineering of the cable system. Rediffusion converted to to all three TV services to 625 line transmission in late 1969. Not so sure how British Relay converted their system to three channel 625 line TV. Again I hope Trevor will enter the debate about BRW 625 line cable TV transmission.

It's rumoured a special French 405-819 line TV receiver was made for use in Northern France and the Channel Islands. Sound IF 39.2 for both TV standards but the vision IFs are totally different. If designing a vision receiver wasn't difficult enough another difficulty must have been designing a line output stage to operate at 10,125Hz and 20,475Hz.
The attachments were posted up on the vintage-radio forum by member "Synchrodyne".

Geordie McBoyne.

[LENINGRAD T2]

Interesting YT video Trevor.

Cable television in the UK created, as I see it, a powerful infrastructure. I suppose that the quality of the signal delivered this way was better than the air. A huge number of people had to operate this system. Is the cabling of this network used for anything today?

"Vision carrier was 4.95Mhz" - this value is lower than in the air

The 405/819 television receiver could be produced by, for example, Pye. In 1958, its engineers created a television set for Poland and Sweden operating in a 625-line system. It wasn't a big production. This proves a certain technological "flexibility" of Pye. These are of course my speculations. I also found something like this:

   

Is it only 819?

[Murphyv310]

Thanks Adam.
My home town of Kilmarnock is even seen in the video.... Well just the town's sign on the road.
On 405 the vision carrier for the British Relay line system was 3.5mhz (some radio amateurs complained of breakthrough on 80 meters) the TV sound was at 2.01 MHz. Radio was at AF fed from 4, 1 kilowatt valve amplifiers.
Once 625 line colour started, only the vision carrier was changed to 4.43mhz and the colour subcarrier was 8.86mhz, all picked for a sound reason of being able to lock the carriers so there were no artifacts of hue changes if there was slight breakthrough on the very long cable runs (MVF) that could be noticeable on screen.
A lot to remember from the 70s

[DrStrangelove]

The cable tv here was run by Red Dragon Relays which had started before WWII as a cable wireless system run by a pharmacist.

The tv side of it was distributed across Band I and Band III and gave alternative options to the local Welsh variety of BBC Wales and TWW (ITV in the pre Harlech days) plus Westward TV which served the south west in Devon/Cornwall.

Due to the nature of the terrain, the valleys were poorly served with tv and the cable system ran for decades until it was taken over by Radio Rentals in the 1970s.

TV sets were either equipped with suitable tuners (the dual standard ones were an easy conversion) or for single standard sets with UHF tuners the option was the Televerter which translated the Band I & Band III signals to UHF.

Down in the shed there's the woodworm riddled remains of a Pye dual standard set which has a system switch that selects 405, 625 on VHF, or 625 on UHF.

[Geordie McBoyne]

TV licences issued in the UK by March 1961. Almost every set was at that time a 405 line only receiver. Later that year the first dual-standard 405-625 receivers were the Pye V700D and the Ekco T398. Other manufacturers played safe and produced convertible sets.

Geordie McBoyne.

[Richard_FM]

I imagine some early 405 - 625 line dual standard sets were made at first for the Irish market, with the option to tune to 625 lines on VHF.

[Mike Watterson]

But in Ireland the people in 625 areas would not have been able to pick up 405. In the Irish 405 areas (existing due to those people already having 405 for BBC & ITV) there was no UK 625 to pick up till some years later and the further away from east coast and Border Irish 625 would not have been easily received, or not at all. Irish TV (using 405 OR 625, never both, according to region) started 31st December 1961. BBC 2 was 1964. Not sure when NI (Divis and Strabane?) and Wales got BBC2.
Ireland's 2nd channel wasn't launched till 1978.

Most of the new TVs in 1961-1963 would have been for 625 areas. Dublin was an aircraft hazard with masts for UK BBC/ITV. They even considered a TV licence in the 1950s. By 1962 the uptake of 405 in areas where any sort of giant mast and aerial would get BBC/ITV was very high. Cable TV was driven by BBC/ITV in Dublin and Dublin was once the most cabled city in Europe. The reason for having 405 or 625 (nowhere had both) in Ireland was the existing high takeup of 405 lines and the dual standard sets to allow UK 405 and Irish 625 didn't exist yet anyway.