09-11-2023, 03:06 PM
(This post was last modified: 09-11-2023, 03:06 PM by ppppenguin.)
Recording video on magnetic tape was a subject of much R&D in the 1950s. In the USA, with multiple time zones, it would allow peak time programmes to be shown at the right time in all areas. So it's not surprising that Bing Crosby's company sponsored R&D int he field.
All the early attempts used tape running at very high speed, many feet per second, to allow high frequencies to be recorded. The octave problem is severe for video. A magnetic head's output is proportional to rate of change of flux so low frequencies give much lower output than high ones. Audio needs about 7 octaves, video about 18. This made direct recording impossible so many efforts were made to use carrriers and/or band splitting and multiple tracks to get it to work.
None of these linear systems got beyond lab demos.
The attachment is the first pages of an article from the 1956 volume of RCA Review. It describes successful recording of NTSC colour and refers back to earlier results in 1953.
In 1956 Ampex announced the Quadruplex system, using 2" wide tape at 15 inches per second. https://en.wikipedia.org/wiki/Quadruplex_videotape This was an immediate commercial success.
So what on earth was the BBC doing with VERA (Video Electronic Recording Apparatus) in 1958? It was used just once on air: https://www.youtube.com/watch?v=56V3QPpyOO8 It then sank almost without trace. The Broadcast Engineering Museum will soon hold the largest collection of relics from VERA. That's not saying much! One spool, a control panel and a label. I understand that the Bradford museum has a spool and a tape head.
Why did the BBC pursue the development of VERA well after it was obvious that Quadruplex was the answer? I've no idea. Perhaps they thought it would be cheaper than the very expensive Ampex and RCA machines.
All the early attempts used tape running at very high speed, many feet per second, to allow high frequencies to be recorded. The octave problem is severe for video. A magnetic head's output is proportional to rate of change of flux so low frequencies give much lower output than high ones. Audio needs about 7 octaves, video about 18. This made direct recording impossible so many efforts were made to use carrriers and/or band splitting and multiple tracks to get it to work.
None of these linear systems got beyond lab demos.
The attachment is the first pages of an article from the 1956 volume of RCA Review. It describes successful recording of NTSC colour and refers back to earlier results in 1953.
In 1956 Ampex announced the Quadruplex system, using 2" wide tape at 15 inches per second. https://en.wikipedia.org/wiki/Quadruplex_videotape This was an immediate commercial success.
So what on earth was the BBC doing with VERA (Video Electronic Recording Apparatus) in 1958? It was used just once on air: https://www.youtube.com/watch?v=56V3QPpyOO8 It then sank almost without trace. The Broadcast Engineering Museum will soon hold the largest collection of relics from VERA. That's not saying much! One spool, a control panel and a label. I understand that the Bradford museum has a spool and a tape head.
Why did the BBC pursue the development of VERA well after it was obvious that Quadruplex was the answer? I've no idea. Perhaps they thought it would be cheaper than the very expensive Ampex and RCA machines.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv