View Single Post
  #6  
Old 01-13-2017, 08:15 AM
Robert Grant's Avatar
Robert Grant Robert Grant is offline
VideoKarma Member
 
Join Date: Feb 2008
Location: Monroe County, MI
Posts: 518
British monochrome analog television used only 405 scanning lines and only 25 frames per second, resulting in only 10,125 lines transmitted per second (compared with 15,750 or 15,734.2xx per second for USA analog television). This meant that the British system only needed 5MHz for a television channel instead of America's 6MHz, and yet had more horizontal resolution than American television

This allowed the UK to place eight highband channels 6 through 13 in Band III with two MHz left over.

Note that Britain's five Band I channels ended at 68MHz and that they never had Band II over-the-air television at all.

Unusual about UK television is that it has been through not one, but two, incompatible transitions.

From 1964 to 1985, they had the 405-line VHF to 625 line UHF transition, including television sets in the UK that were dual standard sets, which switched from positive modulation 405-line video with AM audio and -3.5 MHz audio offset, to negative modulation 625-line video with FM audio and +6MHz offset when the user switched from VHF (BBC1 and ITV) to UHF (BBC2).

From November 1969, UHF 625 line transmissions of BBC1 and ITV were added, so television sets made from about 1970 onward had no 405, positive picture detection, AM audio, nor VHF tuner.

The second transition was done like everywhere else in the world. UHF Digital transmitters were shoehorned among UHF analog transmitters with the latter shut down years later and some improvements made to the digital transmitters later.

Last edited by Robert Grant; 01-13-2017 at 09:40 AM.
Reply With Quote