13-03-2023, 11:20 AM
Like any analogue colour TV system, be it NTSC or PAL, without the luxury of comb filters the picture quality will be degraded to a certain extent by the presence of the colour sub-carrier in the video signal. Apart from the more prominent line structure 405 colour won't look any better or worse than any of the other analogue colour TV systems.
The BBC digital 625 to 405 converter uses the LM1596 modulator IC as the sync and blanking mixer. Metal encapsulation version of the more common MC1486.
Video bandwidth of the 405 video is no more than 3.1Mhz. Wasn't the pre-war video bandwidth 2.7Mhz? 5 : 4 aspect ratio. That was when the active video was 83uS. Became 4 : 3 in 1949/50. Later reduced to 80uS, hence the increased video bandwidth requirement.
Geordie McBoyne.
The BBC digital 625 to 405 converter uses the LM1596 modulator IC as the sync and blanking mixer. Metal encapsulation version of the more common MC1486.
Video bandwidth of the 405 video is no more than 3.1Mhz. Wasn't the pre-war video bandwidth 2.7Mhz? 5 : 4 aspect ratio. That was when the active video was 83uS. Became 4 : 3 in 1949/50. Later reduced to 80uS, hence the increased video bandwidth requirement.
Geordie McBoyne.
