27-08-2023, 06:08 PM
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.
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.
