Interlacing for newbs

[DaveWM]

learned some thing new today (being a newbe to TV everthing is new so this is aimed at other newbs).

I noticed that my 24" B&W pictrue was a bit course, while reading some of my fix it your self books I determined it was due to poor interlacing of the two pics of the same frame. there was talk of checking the integrating circuit, but also one of the books mentioned adjusting the vert hold.

Up until now I figured the vert hold was the vert hold and if it was not rolling it was adjusted right. So I adjusted it and sure enough I was able to get a much better pic (you could see the overlapping scans spread apart.

Wow that was easy.

anyway FWIW...

[old_tv_nut]

All sets with a vertical hold control suffered from this to some extent. The problem is due to the high-voltage, high-current horizontal sweep getting into the vertical sync. This is very hard to compensate in any given chassis, since it can be a function of ground loops from the horizontal sweep circuit, and once the chassis and circuits are laid out, trying to fix them could be impossible. Later chassis that used a digital countdown for sync fixed this once and for all, since it could trigger on the edge of a 2x horizontal frequency and therefore start vertical retrace exactly on a whole line or a half line on alternate fields.

In 1953, Motorola even based an ad campaign on the quality of its interlacing.

[DaveWM]

so did motorola really have better interlacing? back in the early 50's anyway.

[old_tv_nut]

Wish I knew